Water in the Atmosphere | Earth Science

<!DOCTYPE html> <html lang="en" dir="ltr"> <head>  <meta http-equiv="X-UA-Compatible" content="ie=edge"> <meta charset="utf-8"> <base href="https://www.visionlearning.com"> <title>Water in the Atmosphere | Earth Science | Visionlearning</title> <link rel="canonical" href="https://www.visionlearning.com/en/library/earth-science/6/water-in-the-atmosphere/289"> <meta name="description" content="Water in the atmosphere is responsible for moving precipitation around the planet and contributing to the characteristics of Earth’s various climatic zones. The amount of water in the atmosphere varies due to daily temperature and pressure changes, as well as from the global prevailing wind directions and speeds. As global temperatures change, the amount of water vapor in the atmosphere will also change."> <meta name="keywords" content="water, atmosphere, hygrometer, precipitation, evaporation, humidity, meteorologist, saturation, trade wind, rain gauge, climatic zones, adiabatic, cloud condensation nuclei"> <meta name="viewport" content="width=device-width, initial-scale=1.0, shrink-to-fit=no"> <meta name="msvalidate.01" content="D8E20F39AD48052260032E56DE409970"> <script type="application/ld+json"> { "@context": "http://schema.org/", "@type": "Article", "mainEntityOfPage": { "@type": "WebPage", "@id": "https://visionlearning.com/en/library/earth-science/6/water-in-the-atmosphere/289" }, "name": "Water in the Atmosphere", "headline": "Water in the Atmosphere: The factors that influence evaporation and condensation", "author": [ { "@type": "Person", "name": "Anne E. Egger, Ph.D." } , { "@type": "Person", "name": "Ulyana Horodyskyj Pena, Ph.D." }], "datePublished": "2023-08-28 11:29:22", "dateModified": "2017-02-12T08:30:00+05:00", "image": { "@type": "ImageObject", "url": "/img/library/moduleImages/mod-image-289.jpg", "width": 696, "height": 464 }, "publisher": { "@type": "Organization", "name": "Visionlearning, Inc.", "logo": { "@type": "ImageObject", "url": "http://visionlearning.com/images/logo.png", "width": 278, "height": 60 } }, "description": "Water is essential to our existence. Human civilizations have worked endlessly to understand and predict rainfall patterns. In this module, we’ll explore the different ways water collects and forms in the atmosphere, along with developments humans have made in measuring and understanding its patterns. Some of these patterns are outside human control, based on planetary features. But we’ve discovered ways our actions have changed water distribution and rainfall. The findings may surprise you.", "keywords": "water, atmosphere, hygrometer, precipitation, evaporation, humidity, meteorologist, saturation, trade wind, rain gauge, climatic zones, adiabatic, cloud condensation nuclei", "inLanguage": { "@type": "Language", "name": "English", "alternateName": "en" }, "copyrightHolder": { "@type": "Organization", "name": "Visionlearning, Inc." }, "copyrightYear": "2023"} </script> <meta property="og:url" content="https://visionlearning.com/en/library/earth-science/6/water-in-the-atmosphere/289"> <meta property="og:title" content="Water in the Atmosphere | Earth Science | Visionlearning" /> <meta property="og:type" content="website"> <meta property="og:site_name" content="Visionlearning"> <meta property="og:description" content="Water in the atmosphere is responsible for moving precipitation around the planet and contributing to the characteristics of Earth’s various climatic zones. The amount of water in the atmosphere varies due to daily temperature and pressure changes, as well as from the global prevailing wind directions and speeds. As global temperatures change, the amount of water vapor in the atmosphere will also change."> <meta property="og:image" content="https://visionlearning.com/images/logo.png"> <meta property="fb:admins" content="100000299664514"> <link rel="stylesheet" type="text/css" href="/css/visionlearning.css">  <link rel="stylesheet" type="text/css" href="/css/visionlearning-icons.css">  <link rel="preconnect" as="font" href="https://fonts.gstatic.com" crossorigin> <link href="https://fonts.googleapis.com/css2?family=Open+Sans:ital,wght@0,400;0,700;1,400;1,700&family=Schoolbell&display=swap" rel="stylesheet"> <style> textarea.myEditor { width: 90%; height: 350px; } </style> <script type="text/x-mathjax-config" src="/js/mathjax-config.js"></script> <script id="MathJax-script" async src="/js/mathjax/tex-svg.js"></script> <script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-9561344156007092" crossorigin="anonymous"></script> </head> <body>  <header 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href="/en/library/earth-science/6/factors-that-control-earths-temperature/234">Factors that Control Earth's Temperature</a></li> <li><a href="/en/library/earth-science/6/circulation-in-the-atmosphere/255">Circulation in the Atmosphere</a></li> </ul> </div> <button class="accordion__button" id="acc-button-hazards" data-accordion="button" aria-controls="acc-panel-hazards" aria-expanded="false"> <span class="accordion__button__label"> Hazards </span> </button> <div class="accordion__panel" id="acc-panel-hazards" data-accordion="panel" aria-labelledby="acc-button-hazards" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/earth-science/6/natural-hazards-and-risk/288">Natural Hazards and Risk</a></li> </ul> </div> <button class="accordion__button" id="acc-button-earth-history" data-accordion="button" aria-controls="acc-panel-earth-history" aria-expanded="false"> <span class="accordion__button__label"> Earth History </span> </button> <div class="accordion__panel" 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aria-controls="acc-panel-ecology" aria-expanded="false"> <span class="accordion__button__label"> Ecology </span> </button> <div class="accordion__panel" id="acc-panel-ecology" data-accordion="panel" aria-labelledby="acc-button-ecology" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/environmental-science/61/biodiversity-i/276">Biodiversity I</a></li> <li><a href="/en/library/environmental-science/61/biodiversity-ii/281">Biodiversity II</a></li> <li><a href="/en/library/environmental-science/61/ecosystem-services/279">Ecosystem Services</a></li> <li><a href="/en/library/environmental-science/61/population-biology/287">Population Biology</a></li> </ul> </div> <button class="accordion__button" id="acc-button-earth-cycles" data-accordion="button" aria-controls="acc-panel-earth-cycles" aria-expanded="false"> <span class="accordion__button__label"> Earth Cycles </span> </button> <div class="accordion__panel" id="acc-panel-earth-cycles" data-accordion="panel" aria-labelledby="acc-button-earth-cycles" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/environmental-science/61/the-nitrogen-cycle/98">The Nitrogen Cycle</a></li> <li><a href="/en/library/environmental-science/61/the-carbon-cycle/95">The Carbon Cycle</a></li> <li><a href="/en/library/environmental-science/61/the-phosphorus-cycle/197">The Phosphorus Cycle</a></li> </ul> </div> <button class="accordion__button" id="acc-button-scientific-research" data-accordion="button" aria-controls="acc-panel-scientific-research" aria-expanded="false"> <span class="accordion__button__label"> Scientific Research </span> </button> <div class="accordion__panel" id="acc-panel-scientific-research" data-accordion="panel" aria-labelledby="acc-button-scientific-research" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/environmental-science/61/collaborative-research-in-the-arctic-towards-understanding-climate-change/183">Collaborative Research in the Arctic Towards Understanding Climate Change</a></li> <li><a href="/en/library/environmental-science/61/atmospheric-chemistry-research-that-changed-global-policy/211">Atmospheric Chemistry Research that Changed Global Policy</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-general-science" data-accordion="button" aria-controls="acc-panel-general-science" aria-expanded="false"> <span class="accordion__button__label"> General Science </span> </button> <div class="accordion__panel" id="acc-panel-general-science" data-accordion="panel" aria-labelledby="acc-button-general-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-methods" data-accordion="button" aria-controls="acc-panel-methods" aria-expanded="false"> <span class="accordion__button__label"> Methods </span> </button> <div class="accordion__panel" id="acc-panel-methods" data-accordion="panel" aria-labelledby="acc-button-methods" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/the-scientific-method/45">The Scientific Method</a></li> </ul> </div> <button class="accordion__button" id="acc-button-measurement" data-accordion="button" aria-controls="acc-panel-measurement" aria-expanded="false"> <span class="accordion__button__label"> Measurement </span> </button> <div class="accordion__panel" id="acc-panel-measurement" data-accordion="panel" aria-labelledby="acc-button-measurement" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/the-metric-system/47">The Metric System</a></li> </ul> </div> <button class="accordion__button" id="acc-button-physical-properties" data-accordion="button" aria-controls="acc-panel-physical-properties" aria-expanded="false"> <span class="accordion__button__label"> Physical Properties </span> </button> <div class="accordion__panel" id="acc-panel-physical-properties" data-accordion="panel" aria-labelledby="acc-button-physical-properties" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/temperature/48">Temperature</a></li> <li><a href="/en/library/general-science/3/density-and-buoyancy/37">Density and Buoyancy</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-math-in-science" data-accordion="button" aria-controls="acc-panel-math-in-science" aria-expanded="false"> <span class="accordion__button__label"> Math in Science </span> </button> <div class="accordion__panel" id="acc-panel-math-in-science" data-accordion="panel" aria-labelledby="acc-button-math-in-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-equations" data-accordion="button" aria-controls="acc-panel-equations" aria-expanded="false"> <span class="accordion__button__label"> Equations </span> </button> <div class="accordion__panel" id="acc-panel-equations" data-accordion="panel" aria-labelledby="acc-button-equations" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/unit-conversion/144">Unit Conversion</a></li> <li><a href="/en/library/math-in-science/62/linear-equations/194">Linear Equations</a></li> <li><a href="/en/library/math-in-science/62/exponential-equations-i/206">Exponential Equations I</a></li> <li><a href="/en/library/math-in-science/62/exponential-equations-ii/210">Exponential Equations II</a></li> <li><a href="/en/library/math-in-science/62/scientific-notation/250">Scientific Notation</a></li> <li><a href="/en/library/math-in-science/62/measurement/257">Measurement</a></li> </ul> </div> <button class="accordion__button" id="acc-button-statistics" data-accordion="button" aria-controls="acc-panel-statistics" aria-expanded="false"> <span class="accordion__button__label"> Statistics </span> </button> <div class="accordion__panel" id="acc-panel-statistics" data-accordion="panel" aria-labelledby="acc-button-statistics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/introduction-to-descriptive-statistics/218">Introduction to Descriptive Statistics</a></li> <li><a href="/en/library/math-in-science/62/introduction-to-inferential-statistics/224">Introduction to Inferential Statistics</a></li> <li><a href="/en/library/math-in-science/62/statistical-techniques/239">Statistical Techniques</a></li> </ul> </div> <button class="accordion__button" id="acc-button-trigonometric-functions" data-accordion="button" aria-controls="acc-panel-trigonometric-functions" aria-expanded="false"> <span class="accordion__button__label"> Trigonometric Functions </span> </button> <div class="accordion__panel" id="acc-panel-trigonometric-functions" data-accordion="panel" aria-labelledby="acc-button-trigonometric-functions" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/wave-mathematics/131">Wave Mathematics</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-physics" data-accordion="button" aria-controls="acc-panel-physics" aria-expanded="false"> <span class="accordion__button__label"> Physics </span> </button> <div class="accordion__panel" id="acc-panel-physics" data-accordion="panel" aria-labelledby="acc-button-physics" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-light-and-optics" data-accordion="button" aria-controls="acc-panel-light-and-optics" aria-expanded="false"> <span class="accordion__button__label"> Light and Optics </span> </button> <div class="accordion__panel" id="acc-panel-light-and-optics" data-accordion="panel" aria-labelledby="acc-button-light-and-optics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/physics/24/the-nature-of-light/132">The Nature of Light</a></li> <li><a href="/en/library/physics/24/electromagnetism-and-light/138">Electromagnetism and Light</a></li> </ul> </div> <button class="accordion__button" id="acc-button-mechanics" data-accordion="button" aria-controls="acc-panel-mechanics" aria-expanded="false"> <span class="accordion__button__label"> Mechanics </span> </button> <div class="accordion__panel" id="acc-panel-mechanics" data-accordion="panel" aria-labelledby="acc-button-mechanics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/physics/24/defining-energy/199">Defining Energy</a></li> <li><a href="/en/library/physics/24/waves-and-wave-motion/102">Waves and Wave Motion</a></li> <li><a href="/en/library/physics/24/gravity/118">Gravity</a></li> <li><a href="/en/library/physics/24/thermodynamics-i/200">Thermodynamics I</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-process-of-science" data-accordion="button" aria-controls="acc-panel-process-of-science" aria-expanded="false"> <span class="accordion__button__label"> Process of Science </span> </button> <div class="accordion__panel" id="acc-panel-process-of-science" data-accordion="panel" aria-labelledby="acc-button-process-of-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-introduction" data-accordion="button" aria-controls="acc-panel-introduction" aria-expanded="false"> <span class="accordion__button__label"> Introduction </span> </button> <div class="accordion__panel" id="acc-panel-introduction" data-accordion="panel" aria-labelledby="acc-button-introduction" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-process-of-science/176">The Process of Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-the-culture-of-science" data-accordion="button" aria-controls="acc-panel-the-culture-of-science" aria-expanded="false"> <span class="accordion__button__label"> The Culture of Science </span> </button> <div class="accordion__panel" id="acc-panel-the-culture-of-science" data-accordion="panel" aria-labelledby="acc-button-the-culture-of-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-nature-of-scientific-knowledge/185">The Nature of Scientific Knowledge</a></li> <li><a href="/en/library/process-of-science/49/scientists-and-the-scientific-community/172">Scientists and the Scientific Community</a></li> <li><a href="/en/library/process-of-science/49/scientific-ethics/161">Scientific Ethics</a></li> <li><a href="/en/library/process-of-science/49/scientific-institutions-and-societies/162">Scientific Institutions and Societies</a></li> </ul> </div> <button class="accordion__button" id="acc-button-ideas-in-science" data-accordion="button" aria-controls="acc-panel-ideas-in-science" aria-expanded="false"> <span class="accordion__button__label"> Ideas in Science </span> </button> <div class="accordion__panel" id="acc-panel-ideas-in-science" data-accordion="panel" aria-labelledby="acc-button-ideas-in-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/theories-hypotheses-and-laws/177">Theories, Hypotheses, and Laws</a></li> <li><a href="/en/library/process-of-science/49/scientific-controversy/181">Scientific Controversy</a></li> <li><a href="/en/library/process-of-science/49/creativity-in-science/182">Creativity in Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-research-methods" data-accordion="button" aria-controls="acc-panel-research-methods" aria-expanded="false"> <span class="accordion__button__label"> Research Methods </span> </button> <div class="accordion__panel" id="acc-panel-research-methods" data-accordion="panel" aria-labelledby="acc-button-research-methods" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-practice-of-science/148">The Practice of Science</a></li> <li><a href="/en/library/process-of-science/49/experimentation-in-scientific-research/150">Experimentation in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/description-in-scientific-research/151">Description in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/comparison-in-scientific-research/152">Comparison in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/modeling-in-scientific-research/153">Modeling in Scientific Research</a></li> </ul> </div> <button class="accordion__button" id="acc-button-data" data-accordion="button" aria-controls="acc-panel-data" aria-expanded="false"> <span class="accordion__button__label"> Data </span> </button> <div class="accordion__panel" id="acc-panel-data" data-accordion="panel" aria-labelledby="acc-button-data" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/data-analysis-and-interpretation/154">Data Analysis and Interpretation</a></li> <li><a href="/en/library/process-of-science/49/uncertainty-error-and-confidence/157">Uncertainty, Error, and Confidence</a></li> <li><a href="/en/library/process-of-science/49/statistics-in-science/155">Statistics in Science</a></li> <li><a href="/en/library/process-of-science/49/using-graphs-and-visual-data-in-science/156">Using Graphs and Visual Data in Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-scientific-communication" data-accordion="button" aria-controls="acc-panel-scientific-communication" aria-expanded="false"> <span class="accordion__button__label"> Scientific Communication </span> </button> <div class="accordion__panel" id="acc-panel-scientific-communication" data-accordion="panel" aria-labelledby="acc-button-scientific-communication" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/understanding-scientific-journals-and-articles/158">Understanding Scientific Journals and Articles</a></li> <li><a href="/en/library/process-of-science/49/utilizing-the-scientific-literature/173">Utilizing the Scientific Literature</a></li> <li><a href="/en/library/process-of-science/49/peer-review-in-scientific-publishing/159">Peer Review in Scientific Publishing</a></li> <li><a href="/en/library/process-of-science/49/the-how-and-why-of-scientific-meetings/186">The How and Why of Scientific Meetings</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-scientists-and-research" data-accordion="button" aria-controls="acc-panel-scientists-and-research" aria-expanded="false"> <span class="accordion__button__label"> Scientists and Research </span> </button> <div class="accordion__panel" id="acc-panel-scientists-and-research" data-accordion="panel" aria-labelledby="acc-button-scientists-and-research" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-scientific-research" data-accordion="button" aria-controls="acc-panel-scientific-research" aria-expanded="false"> <span class="accordion__button__label"> Scientific Research </span> </button> <div class="accordion__panel" id="acc-panel-scientific-research" data-accordion="panel" aria-labelledby="acc-button-scientific-research" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/scientists-and-research/58/collaborative-research-in-the-arctic-towards-understanding-climate-change/183">Collaborative Research in the Arctic Towards Understanding Climate Change</a></li> <li><a href="/en/library/scientists-and-research/58/from-stable-chromosomes-to-jumping-genes/184">From Stable Chromosomes to Jumping Genes</a></li> <li><a href="/en/library/scientists-and-research/58/an-elegant-experiment-to-test-the-process-of-dna-replication/187">An Elegant Experiment to Test the Process of DNA Replication</a></li> <li><a href="/en/library/scientists-and-research/58/the-founding-of-neuroscience/233">The Founding of Neuroscience</a></li> <li><a href="/en/library/scientists-and-research/58/tracking-endangered-jaguars-across-the-border/189">Tracking Endangered Jaguars across the Border</a></li> <li><a href="/en/library/scientists-and-research/58/atmospheric-chemistry-research-that-changed-global-policy/211">Atmospheric Chemistry Research that Changed Global Policy</a></li> <li><a href="/en/library/scientists-and-research/58/revolutionizing-medicine-with-monoclonal-antibodies/220">Revolutionizing Medicine with Monoclonal Antibodies</a></li> <li><a href="/en/library/scientists-and-research/58/uncovering-the-mysteries-of-chronic-mountain-sickness/238">Uncovering the Mysteries of Chronic Mountain Sickness</a></li> </ul> </div> <button class="accordion__button" id="acc-button-profiles-in-science" data-accordion="button" aria-controls="acc-panel-profiles-in-science" aria-expanded="false"> <span class="accordion__button__label"> Profiles in Science </span> </button> <div class="accordion__panel" id="acc-panel-profiles-in-science" data-accordion="panel" aria-labelledby="acc-button-profiles-in-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/scientists-and-research/58/luis-e.-miramontes/232">Luis E. Miramontes</a></li> <li><a href="/en/library/scientists-and-research/58/bernardo-houssay/237">Bernardo Houssay</a></li> <li><a href="/en/library/scientists-and-research/58/craig-lee/256">Craig Lee</a></li> <li><a href="/en/library/scientists-and-research/58/david-ho/241">David Ho</a></li> <li><a href="/en/library/scientists-and-research/58/louis-tompkins-wright/244">Louis Tompkins Wright</a></li> <li><a href="/en/library/scientists-and-research/58/carlos-j.-finlay/217">Carlos J. Finlay</a></li> <li><a href="/en/library/scientists-and-research/58/cecilia-payne/290">Cecilia Payne</a></li> <li><a href="/en/library/scientists-and-research/58/jazmin-scarlett/291">Jazmin Scarlett</a></li> <li><a href="/en/library/scientists-and-research/58/ramari-stewart/292">Ramari Stewart</a></li> <li><a href="/en/library/scientists-and-research/58/johnson-cerda/300">Johnson Cerda</a></li> <li><a href="/en/library/scientists-and-research/58/ellen-ochoa/201">Ellen Ochoa</a></li> <li><a href="/en/library/scientists-and-research/58/ruth-benerito/205">Ruth Benerito</a></li> <li><a href="/en/library/scientists-and-research/58/franklin-chang-díaz/219">Franklin Chang Díaz</a></li> <li><a href="/en/library/scientists-and-research/58/percy-lavon-julian/221">Percy Lavon Julian</a></li> <li><a href="/en/library/scientists-and-research/58/luis-walter-alvarez/229">Luis Walter Alvarez</a></li> <li><a href="/en/library/scientists-and-research/58/france-anne-dominic-córdova/230">France Anne-Dominic Córdova</a></li> </ul> </div> </div> </div> </div> </div> </li> <li>  <button class="button" data-toggle="dropdown">Earth Science </button> <div class="nav__dropdown box-shadow-1 padding-1"> <div class="accordion accordion--secondary font-size-sm"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-sub-button-plate-tectonics" data-accordion="button" aria-controls="acc-sub-panel-plate-tectonics" aria-expanded="false"> <span class="accordion__button__label"> Plate Tectonics </span> </button> <div class="accordion__panel" id="acc-sub-panel-plate-tectonics" data-accordion="panel" aria-labelledby="acc-sub-button-plate-tectonics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/earth-science/6/origins-of-plate-tectonic-theory/65">Origins of Plate Tectonic Theory</a></li> <li><a href="/en/library/earth-science/6/plate-boundaries/66">Plate Boundaries</a></li> <li><a href="/en/library/earth-science/6/earth-structure/69">Earth Structure</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-earth-cycles" data-accordion="button" aria-controls="acc-sub-panel-earth-cycles" aria-expanded="false"> <span class="accordion__button__label"> Earth Cycles </span> </button> <div class="accordion__panel" id="acc-sub-panel-earth-cycles" data-accordion="panel" aria-labelledby="acc-sub-button-earth-cycles" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/earth-science/6/the-rock-cycle/128">The Rock Cycle</a></li> <li><a href="/en/library/earth-science/6/the-hydrologic-cycle/99">The Hydrologic Cycle</a></li> <li><a href="/en/library/earth-science/6/the-carbon-cycle/95">The Carbon Cycle</a></li> <li><a href="/en/library/earth-science/6/the-nitrogen-cycle/98">The Nitrogen Cycle</a></li> <li><a href="/en/library/earth-science/6/the-phosphorus-cycle/197">The Phosphorus Cycle</a></li> </ul> </div> <button 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class="accordion__panel" id="acc-sub-panel-atmosphere-and-oceans" data-accordion="panel" aria-labelledby="acc-sub-button-atmosphere-and-oceans" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/earth-science/6/ocean-currents/282">Ocean Currents</a></li> <li class="current">Water in the Atmosphere</li> <li><a href="/en/library/earth-science/6/weather-fronts-and-forecasts/303">Weather, Fronts, and Forecasts</a></li> <li><a href="/en/library/earth-science/6/history-of-earths-atmosphere-i/202">History of Earth's Atmosphere I</a></li> <li><a href="/en/library/earth-science/6/history-of-earths-atmosphere-ii/203">History of Earth's Atmosphere II</a></li> <li><a href="/en/library/earth-science/6/earths-atmosphere/107">Earth's Atmosphere</a></li> <li><a href="/en/library/earth-science/6/factors-that-control-earths-temperature/234">Factors that Control Earth's Temperature</a></li> <li><a href="/en/library/earth-science/6/circulation-in-the-atmosphere/255">Circulation in the Atmosphere</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-hazards" data-accordion="button" aria-controls="acc-sub-panel-hazards" aria-expanded="false"> <span class="accordion__button__label"> Hazards </span> </button> <div class="accordion__panel" id="acc-sub-panel-hazards" data-accordion="panel" aria-labelledby="acc-sub-button-hazards" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/earth-science/6/natural-hazards-and-risk/288">Natural Hazards and Risk</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-earth-history" data-accordion="button" aria-controls="acc-sub-panel-earth-history" aria-expanded="false"> <span class="accordion__button__label"> Earth History </span> </button> <div class="accordion__panel" id="acc-sub-panel-earth-history" data-accordion="panel" aria-labelledby="acc-sub-button-earth-history" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/earth-science/6/extinction/295">Extinction</a></li> <li><a href="/en/library/earth-science/6/paleontology-and-the-fossil-record/301">Paleontology and the Fossil Record</a></li> <li><a href="/en/library/earth-science/6/mass-extinctions/294">Mass Extinctions</a></li> </ul> </div> </div> </div> </div> </li> </ul> </nav>  <div id="theTop"></div> <main id="skip-header-content"> <div class="margin-bottom-5"> <div class="container narrow wide--lg margin-y-4"> <article class="module"> <header class="module__header"> <span class="subcategory"> <strong><em>Atmosphere and Oceans</em></strong> </span> <h1>Water in the Atmosphere: <sub><em>The factors that influence evaporation and condensation</em></sub></h1> <p class="byline">by Anne E. Egger, Ph.D., Ulyana Horodyskyj Pena, Ph.D.</p> </header> <nav class="module__tabs"> <ul class="tabs-nav tabs-nav--pill tabs-nav--horizontal--md library"> <li> <a href="/en/library/earth-science/6/water-in-the-atmosphere/289/reading" class="is-active" aria-current="page" >Reading</a> </li> <li> <a href="/en/library/earth-science/6/water-in-the-atmosphere/289/quiz" >Quiz</a> </li> <li> <a href="/en/library/earth-science/6/water-in-the-atmosphere/289/resources" >Teach with this</a> </li> </ul> </nav> <hr class="module__divider" />  <div class="module__tools"> <aside class="module__tools__container border-radius box-shadow-1"> <div class="tabs tabs--toggle-mobile--lg" role="tablist"> <ul class="tab__buttons"> <li> <button class="button button--icon-over-text" aria-label="In this module" aria-controls="tab-panel-module__tools" aria-selected="true" role="tab"> <span class="button__icon"> <span class="icon icon-list" aria-hidden="true"></span> </span> <span class="button__text">Contents</span> </button> </li> <li> <button class="button button--icon-over-text" aria-controls="tab-panel-toggle-terms" aria-selected="false" role="tab"> <span class="button__icon"> <span class="icon icon-glossary-highlight"></span> </span> <span class="button__text">Glossary Terms</span> </button> </li> <li> <button class="button button--icon-over-text" aria-controls="tab-panel-toggle-ngss" aria-selected="false" role="tab"> <span class="button__icon"> <span class="icon icon-ngss" aria-hidden="true"></span> </span> <span class="button__text">NGSS</span> </button> </li> </ul> <div class="tabs__panel shown" id="tab-panel-module__tools" aria-labelledby="tab-button-module__tools" role="tabpanel"> <div class="table-of-contents"> <p class="table-of-contents__title"> Table of Contents </p> <ul class="table-of-contents__nav"> <li><a href="/en/library/earth-science/6/water-in-the-atmosphere/289#toc_1">Introduction</a> </li> <li><a href="/en/library/earth-science/6/water-in-the-atmosphere/289#toc_2">History of measuring water in the atmosphere</a> </li> <li><a href="/en/library/earth-science/6/water-in-the-atmosphere/289#toc_3">Measuring water vapor using hygrometers</a> </li> <li><a href="/en/library/earth-science/6/water-in-the-atmosphere/289#toc_4">How water gets into the atmosphere</a> </li> <li><a href="/en/library/earth-science/6/water-in-the-atmosphere/289#toc_5">How water vapor condenses in the atmosphere</a> </li> <li><a href="/en/library/earth-science/6/water-in-the-atmosphere/289#toc_6">The distribution of precipitation</a> </li> <li><a href="/en/library/earth-science/6/water-in-the-atmosphere/289#toc_7">Measuring and influencing water in the atmosphere</a> </li> <li><a href="/en/library/earth-science/6/water-in-the-atmosphere/289#toc_8">The human influence</a> </li> </ul> </div> </div> <div class="tabs__panel" id="tab-panel-toggle-terms" aria-labelledby="tab-button-toggle-terms" role="tabpanel"> <div class="reading-toggle"> <div class="reading-toggle__switch"> <div class="form-entry__option__switch"> <label> <input type="checkbox" name="termsToggleSwitch" id="terms-toggle-switch" /> <span class="switch__slider"></span> <span class="option__label text-decoration-none font-size-md"> Highlight Glossary Terms </span> </label> </div> </div> <div class="reading-toggle__help"> <p> <em> Activate glossary term highlighting to easily identify key terms within the module. Once highlighted, you can click on these terms to view their definitions. </em> </p> </div> </div> <div class="glossary-container"></div> </div> <div class="tabs__panel" id="tab-panel-toggle-ngss" aria-labelledby="tab-button-toggle-ngss" role="tabpanel"> <div class="reading-toggle"> <div class="reading-toggle__switch"> <div class="form-entry__option__switch"> <label> <input type="checkbox" name="ngssToggleSwitch" id="ngss-toggle-switch" /> <span class="switch__slider"></span> <span class="option__label text-decoration-none font-size-md"> Show NGSS Annotations </span> </label> </div> </div> <div class="reading-toggle__help"> <p> <em> Activate NGSS annotations to easily identify NGSS standards within the module. Once highlighted, you can click on them to view these standards. </em> </p> </div> </div> <div class="ngss-container"></div> </div> </div> </aside> <div class="margin-3"> <script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-9561344156007092" crossorigin="anonymous"></script>  <ins class="adsbygoogle" style="display:block" data-ad-client="ca-pub-9561344156007092" data-ad-slot="7634263342" data-ad-format="auto" data-full-width-responsive="true"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> </div> </div>     <div class="module__main"> <div class="module__main__container"> <div class="accordion">  <button class="accordion__button" id="acc-button-key-concepts" data-accordion="button" aria-controls="acc-panel-key-concepts" aria-expanded="true" tabindex="0"> Did you know? </button> <div class="accordion__panel shown show" id="acc-panel-key-concepts" data-accordion="panel" aria-labelledby="acc-button-key-concepts" role="region"> <div class="accordion__panel__content"> <p>Have you ever noticed your hair becomes frizzy when it's humid outside? Did you know this occurrence was the basis for one scientist inventing a tool to measure humidity? Though it was invented hundreds of years ago, the device is still used by scientists today. It's just one of the many ways we measure water in the atmosphere.</p> </div> </div>  <button class="accordion__button" id="acc-button-table-of-contents" data-accordion="button" aria-controls="acc-panel-table-of-contents" aria-expanded="false" tabindex="0"> Key concepts </button> <div class="accordion__panel" id="acc-panel-table-of-contents" data-accordion="panel" aria-labelledby="acc-button-table-of-contents" role="region" aria-hidden="true"> <div class="accordion__panel__content"> <ul class="bulleted"> <li><p>The rate of evaporation from Earth’s surface is determined by the air temperature, water temperature, wind, and the amount of water vapor already in the air. These factors vary regionally and change over a wide range of timescales on Earth.</p></li> <li><p>As warm, saturated air rises and cools, it leads to the condensation of water vapor into liquid droplets and the formation of clouds. This process determines the amount of precipitation in different regions of the planet.</p></li> <li><p>Using observations from weather balloons and satellites, scientists can map the amount of water vapor in the atmosphere and show that it circulates in predictable patterns, contributing to the characteristics of Earth’s climatic zones.</p></li> </ul> </div> </div>  <button class="accordion__button" id="acc-button-terms-you-should-know" data-accordion="button" aria-controls="acc-panel-terms-you-should-know" aria-expanded="false" tabindex="0"> Terms you should know </button> <div class="accordion__panel" id="acc-panel-terms-you-should-know" data-accordion="panel" aria-labelledby="acc-button-terms-you-should-know" role="region" aria-hidden="true"> <div class="accordion__panel__content"> <dl> <dt><a href="/en/glossary/view/atmosphere">Atmosphere </a></dt> <dd> The collective mass of gasses that surrounds the Earth or another planet </dd> <dt><a href="/en/glossary/view/precipitation">Precipitation </a></dt> <dd> Water that falls from the atmosphere to the ground in any form, such as rain, snow, hail, or sleet </dd> <dt><a href="/en/glossary/view/latitude">Latitude </a></dt> <dd> The angular distance of a place north or south of the Earth’s equator, expressed in degrees </dd> <dt>Meteorologist </dt> <dd> An expert in the study of the atmosphere, including the processes that cause particular weather conditions </dd> <dt><a href="/en/glossary/view/climatic+zones">Climatic zones </a></dt> <dd> Areas characterized by distinct climates that correspond either with weather patterns, latitude, or communities of plants and animals</dd> </dl> </div> </div> </div> <section> <section id="toc_1" class=""> <h2>Introduction</h2> <p>The Hawaiian Islands lie in the middle of the Pacific Ocean at about 19° N <mark class="term" data-term="latitude" data-term-def="the angular distance of a place north or south of the Earth’s equator, expressed in degrees, minutes and seconds." data-term-url="/en/glossary/view/latitude/12930">latitude</mark>. Hawai’i, the “Big Island” furthest to the southeast, is home to the small cities of Hilo on the east coast and Kailua-Kona on the west coast (Figure 1). The cities are roughly 100 kilometers (60 miles) apart and connected by Saddle Road, which winds between Mauna Kea and Mauna Loa, two major volcanic mountains that form the island. Despite the proximity of these cities, one thing about them is very different: While a <mark class="term" data-term="rain gauge" data-term-def="a device for collecting and measuring the amount of falling precipitation." data-term-url="/en/glossary/view/rain+gauge/12933">rain gauge</mark> at the Hilo airport collects approximately 3.3 meters (3300 millimeters) of <mark class="term" data-term="precipitation" data-term-def="Water that falls from the atmosphere to the ground in any form, such as rain, snow, hail, or sleet." data-term-url="/en/glossary/view/precipitation/8562">precipitation</mark> annually, the one at Kailua-Kona collects 0.3 meters (300 millimeters) in the same time <mark class="term" data-term="period" data-term-def="A row of elements in the periodic table." data-term-url="/en/glossary/view/period/8565">period</mark> (Figure 1). Why do two cities less than an hour’s drive from each other have a ten-fold difference in the amount of rain they receive?</p>  <div class="figure"> <figure> <button class="lightbox-button" data-lightbox-src="/img/library/large_images/image_12909.png" data-lightbox="image"> <img src="/img/library/modules/mid289/Image/VLObject12909-23080801081140.png" alt="Figure 1: Annual average rainfall in mm/year on the Big Island of Hawai’i. Rainfall data are from The Online Rainfall Atlas of Hawaii." /> </button> <figcaption> <p><strong>Figure 1:</strong> Annual average rainfall in mm/year on the Big Island of Hawai’i. Rainfall data are from The Online Rainfall Atlas of Hawaii.</p> <span class="credit">image ©<a href="https://journals.ametsoc.org/view/journals/bams/94/3/bams-d-11-00228.1.xml"> Giambelluca et al., 2013</a> </span> </figcaption> </figure> </div> <p><mark id="ngss-599" class="ngss"> This is a big difference on a small island, and we see even bigger differences as we look at other locations around the world. Think about <mark class="term" data-term="precipitation" data-term-def="Water that falls from the atmosphere to the ground in any form, such as rain, snow, hail, or sleet." data-term-url="/en/glossary/view/precipitation/8562">precipitation</mark> where you live. How often does it rain? How much rain or snow falls in a year? When it’s not raining, is the air where you live dry, or does it feel damp? How often is it cloudy? You might think about precipitation, clouds, and humidity as you prepare to go to school or to <mark class="term" data-term="work" data-term-def="A process that occurs when a force acts over a distance, as when an object is moved. Work equals the multiple&hellip;" data-term-url="/en/glossary/view/work/1502">work</mark> for the day—will you be comfortable going outside? Should you bring a raincoat or umbrella?</mark></p> <p>Precipitation, clouds, and humidity are all examples of water in the <mark class="term" data-term="atmosphere" data-term-def="The collective mass of gases that surrounds the Earth or another planet." data-term-url="/en/glossary/view/atmosphere/8529">atmosphere</mark>. The amount and nature of water in the atmosphere vary based on <mark class="term" data-term="latitude" data-term-def="the angular distance of a place north or south of the Earth’s equator, expressed in degrees, minutes and seconds." data-term-url="/en/glossary/view/latitude/12930">latitude</mark>, geographic setting, and regional climate: some parts of the world are wetter and cloudier than others. The amount and nature (or “phase”) of water in the atmosphere also change over time as water moves through the atmosphere. <mark class="term" data-term="learning" data-term-def="The influence of action based off individual experience over time." data-term-url="/en/glossary/view/learning/13154">Learning</mark> more about these processes will help us explain why the eastern side of the Big Island is so much wetter than the western side.</p></section> <section id="toc_2"> <h2>History of measuring water in the atmosphere</h2><p><mark id="ngss-600" class="ngss"> Human societies have long been concerned with understanding precipitation—how much will fall and when—because rain is critical for growing food. For example, on the Big Island of Hawai’i, historic sugarcane plantations were all on the eastern (Hilo) side of the island. Sugarcane depends on large amounts of rainfall to thrive, and the plantations maintained rigorous observational <mark class="term" data-term="record" data-term-def="A written account or description. <br> <b>[verb]</b> To write an account or description." data-term-url="/en/glossary/view/record/8239">records</mark> (Giambelluca et al., 2013).</mark></p> <p><mark id="ngss-601" class="ngss">Rain gauges provide a way to collect and measure fallen <mark class="term" data-term="precipitation" data-term-def="Water that falls from the atmosphere to the ground in any form, such as rain, snow, hail, or sleet." data-term-url="/en/glossary/view/precipitation/8562">precipitation</mark>.</mark> The first known rainfall records date back to the ancient Greeks. But the earliest <mark class="term" data-term="rain gauge" data-term-def="a device for collecting and measuring the amount of falling precipitation." data-term-url="/en/glossary/view/rain+gauge/12933">rain gauge</mark> is credited to King Sejong of Korea in the early 1400s, who mounted bronze canisters of uniform size on posts at observatories across the region (Figure 2). Officials at the observatories would observe the precipitation in these canisters and report back to the King. Based on these <mark class="term" data-term="observation" data-term-def="1. The act of noticing something. 2. A record of that which has been noticed." data-term-url="/en/glossary/view/observation/8255">observations</mark>, court officials would determine the potential harvest and, thus, how much the farmers in the region should be taxed.</p> <div class="container margin-y-4 text-align-center"> <script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-9561344156007092" crossorigin="anonymous"></script>  <ins class="adsbygoogle" style="display:inline-block;width:300px;height:250px" data-ad-client="ca-pub-9561344156007092" data-ad-slot="9090201191"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> </div>  <div class="figure"> <figure> <button class="lightbox-button" data-lightbox-src="/img/library/large_images/image_12910.jpeg" data-lightbox="image"> <img src="/img/library/modules/mid289/Image/VLObject12910-23080801081416.jpg" alt="Figure 2: A modern installation of a rain gauge from the era of King Sejong in Korea, displayed in the Jang Yeong Sil Science Garden in Busan." /> </button> <figcaption> <p><strong>Figure 2:</strong> A modern installation of a rain gauge from the era of King Sejong in Korea, displayed in the Jang Yeong Sil Science Garden in Busan.</p> <span class="credit">image ©<a href="https://commons.wikimedia.org/wiki/File:Jang_Yeong-sil_Science_Garden-Rain_Gauges_13-11789_Busan,_South_Korea_03.JPG"> CC-BY-SA-3.0 Steve46814</a> </span> </figcaption> </figure> </div> <p>Later versions of the <mark class="term" data-term="rain gauge" data-term-def="a device for collecting and measuring the amount of falling precipitation." data-term-url="/en/glossary/view/rain+gauge/12933">rain gauge</mark> included features like funnels that channeled water into a bucket which tipped when it was full, allowing for more accurate measurements of the amount of <mark class="term" data-term="precipitation" data-term-def="Water that falls from the atmosphere to the ground in any form, such as rain, snow, hail, or sleet." data-term-url="/en/glossary/view/precipitation/8562">precipitation</mark>. Modifications allow for measurement of snow and hail in addition to rain.</p> <p><mark id="ngss-602" class="ngss">Rain gauges are still widely used today as one component of modern weather stations and remain relatively simple, with a funnel directing the water into a calibrated canister (Figure 3). However, the purposes of measuring precipitation today are about something other than crop taxation. Instead, measurements from <mark class="term" data-term="network" data-term-def="An interconnected system; an interrelated net-like arrangement of parts." data-term-url="/en/glossary/view/network/8740">networks</mark> of rain gauges are used for weather forecasting, as long-term <mark class="term" data-term="record" data-term-def="A written account or description. <br> <b>[verb]</b> To write an account or description." data-term-url="/en/glossary/view/record/8239">records</mark> of precipitation help us understand how <mark class="term" data-term="climate" data-term-def="Climate describes the average and patterns of a particular area’s weather over time. Climate includes such elements as temperature, precipitation, humidity,&hellip;" data-term-url="/en/glossary/view/climate/9334">climate</mark> is changing over time. Because precipitation can vary so much even in a small geographic area, these forecasts and predictions benefit from many rain gauges, more than any one <mark class="term" data-term="group" data-term-def="A column of elements in the periodic table." data-term-url="/en/glossary/view/group/8566">group</mark> or agency can install and maintain.</mark> To address this need, a grassroots organization called <a href="https://www.cocorahs.org/Application.aspx">CoCoRaHS</a> (pronounced KO-ko-rozz and stands for the Community Collaborative Rain, Hail and Snow Network) began in 1998 at the Colorado Climate Center, hosted by Colorado State University. A flood in Fort Collins, where the university is based, prompted the <mark class="term" data-term="development" data-term-def="The gradual exposure to stimuli in the early-developmental stages that influences the size, shape, and function of animal once mature." data-term-url="/en/glossary/view/development/13147">development</mark> of the organization. Currently, CoCoRaHS has more than 25,000 active observers. Anyone can participate in making precipitation <mark class="term" data-term="observation" data-term-def="1. The act of noticing something. 2. A record of that which has been noticed." data-term-url="/en/glossary/view/observation/8255">observations</mark> that are important to the network, and many thousands of people report their observations on any given day (Figure 4).</p>  <div class="figure"> <figure> <button class="lightbox-button" data-lightbox="image"> <img src="/img/library/modules/mid289/Image/VLObject12911-23080801081642.jpg" alt="Figure 3: A 4” plastic rain gauge, typical of those used at CoCoRaHS observing stations." /> </button> <figcaption> <p><strong><strong>Figure 3:</strong> </strong>A 4” plastic rain gauge, typical of those used at CoCoRaHS observing stations.</p> <span class="credit">image ©<a href="https://commons.wikimedia.org/wiki/File:2013-06-24_17_39_11_A_4-inch_plastic_rain_gauge_typical_of_those_used_by_the_CoCoRaHS_program.jpg"> Famartin</a> </span> </figcaption> </figure> </div>  <div class="figure"> <figure> <button class="lightbox-button" data-lightbox-src="/img/library/large_images/image_12912.png" data-lightbox="image"> <img src="/img/library/modules/mid289/Image/VLObject12912-23080801081931.png" alt="Figure 4: An example of reports from CoCoRAHs users on 2 July 2023. A total of nearly 11,700 observations were submitted on this day." /> </button> <figcaption> <p><strong>Figure 4:</strong> An example of reports from CoCoRAHs users on 2 July 2023. A total of nearly 11,700 observations were submitted on this day.</p> <span class="credit">image ©<a href="https://www.cocorahs.org/ "> CC BY 3.0 CoCoRAHs</a> </span> </figcaption> </figure> </div> <p>Precipitation may be the most obvious form of water in the atmosphere: we can see <mark class="term" data-term="liquid" data-term-def="The state of matter characterized by its condensed nature and ability to flow. Unlike gases, molecules within a liquid often experience&hellip;" data-term-url="/en/glossary/view/liquid/8727">liquid</mark> water actively falling from the sky and feel ourselves get wet. <mark class="term" data-term="precipitation" data-term-def="Water that falls from the atmosphere to the ground in any form, such as rain, snow, hail, or sleet." data-term-url="/en/glossary/view/precipitation/8562">Precipitation</mark> is also relatively easy to measure, but it is only a small proportion of the water that exists in the <mark class="term" data-term="atmosphere" data-term-def="The collective mass of gases that surrounds the Earth or another planet." data-term-url="/en/glossary/view/atmosphere/8529">atmosphere</mark>. Instead, most water is in the vapor phase in the atmosphere (see our <a href="https://www.visionlearning.com/en/library/Earth-Science/6/Composition-of-Earths-Atmosphere/107">Composition of Earth’s Atmosphere</a> module).</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form name="cc12871"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">Forecasts and predictions benefit from many rain gauges because _______.</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-12871-0-option-a" name="quiz-option-12871" type="radio" value="precipitation can vary greatly in a small area" > <span class="option__label"> <span class="screen-reader-only">a.</span> precipitation can vary greatly in a small area </span> </label> <span class="quiz__response" id="response-12871-0"> <strong>Correct!</strong> </span> </div> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-12871-1-option-b" name="quiz-option-12871" type="radio" value="rain gauges are inaccurate in measuring precipitation" > <span class="option__label"> <span class="screen-reader-only">b.</span> rain gauges are inaccurate in measuring precipitation </span> </label> <span class="quiz__response" id="response-12871-1"> <strong>Incorrect.</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_3"> <h2>Measuring water vapor using hygrometers</h2><p><mark id="ngss-603" class="ngss">Water in the vapor phase is invisible. It is also more difficult to measure than <mark class="term" data-term="precipitation" data-term-def="Water that falls from the atmosphere to the ground in any form, such as rain, snow, hail, or sleet." data-term-url="/en/glossary/view/precipitation/8562">precipitation</mark> and more important for weather forecasting. Accurate measurements of the amount of water vapor in the air, called “humidity,” can help forecast rapid phase changes of water in the <mark class="term" data-term="atmosphere" data-term-def="The collective mass of gases that surrounds the Earth or another planet." data-term-url="/en/glossary/view/atmosphere/8529">atmosphere</mark>, including cloud formation and precipitation.</mark></p> <p><mark id="ngss-604" class="ngss">One of the earliest descriptions of an instrument for measuring humidity (also known as a “hygrometer”)</mark> is in a Chinese Han Dynasty <mark class="term" data-term="manuscript" data-term-def="An article or other document submitted or considered for publication." data-term-url="/en/glossary/view/manuscript/8245">manuscript</mark> from 120 <mark class="term" data-term="BCE" data-term-def="An abbreviation for Before the Common Era, which is a designation for the years prior to year 1 of the Gregorian&hellip;" data-term-url="/en/glossary/view/BCE/3720">BCE</mark>. Unlike a <mark class="term" data-term="rain gauge" data-term-def="a device for collecting and measuring the amount of falling precipitation." data-term-url="/en/glossary/view/rain+gauge/12933">rain gauge</mark>, which measures <mark class="term" data-term="liquid" data-term-def="The state of matter characterized by its condensed nature and ability to flow. Unlike gases, molecules within a liquid often experience&hellip;" data-term-url="/en/glossary/view/liquid/8727">liquid</mark> water directly, <mark class="term" data-term="hygrometer" data-term-def="an instrument capable of measuring the relative humidity of the air, or extent to which the air is saturated." data-term-url="/en/glossary/view/hygrometer/12929">hygrometers</mark> measure water vapor indirectly, making use of the fact that some substances <mark class="term" data-term="absorb" data-term-def="Take in or soak up (energy, liquids, or other substances), usually gradually, through a chemical or physical action." data-term-url="/en/glossary/view/absorb/11219">absorb</mark> water vapor more readily than others. The Han Dynasty instrument consisted of equal masses of feathers and charcoal hanging in balance. Charcoal readily absorbs water vapor, whereas feathers do not. When the amount of water vapor in the air increased, the charcoal would absorb more and become heavier, hanging below the feathers. When the humidity decreased, the water absorbed by the charcoal would evaporate, and the charcoal would become lighter, regaining balance with the feathers.</p> <p>Later inventors and cultures used the same <mark class="term" data-term="principle" data-term-def="In the sciences, a principle is a fundamental, primary, or general law or truth. For instance, one of the most basic&hellip;" data-term-url="/en/glossary/view/principle/5289">principle</mark> (that some materials absorb water more readily than others) to develop more precise hygrometers, allowing observers to <mark class="term" data-term="quantify" data-term-def="To express something in terms of a number value, measurement, or amount." data-term-url="/en/glossary/view/quantify/8237">quantify</mark> the amount of water vapor rather than just visualize it. In 1480, Leonardo da Vinci placed beeswax, a waterproof material that doesn’t change due to moisture, in one balance pan and a cotton ball that could absorb moisture in the other pan. If the cotton absorbed moisture from the air, its <mark class="term" data-term="weight" data-term-def="A measure of the force exerted on an object by a gravitational field. The weight of an object equals its mass&hellip;" data-term-url="/en/glossary/view/weight/3418">weight</mark> increased, tipping the balance. An observer could measure the difference with a measuring stick.</p> <p><mark id="ngss-605" class="ngss">A few hundred years later, Swiss physicist and geologist Horace Benedict de Saussure observed that strands of human hair lengthen by as much as 2% as the humidity increases. You may have noticed this effect, especially if you have long hair: On a humid day, your hair might be curlier or “frizzy” as water <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecules</mark> are incorporated into its structure. Saussure used this knowledge to invent the hair hygrometer, which is still in use today as it can react quickly to changes in humidity. These are the only <mark class="term" data-term="mechanical" data-term-def="Involving physical force or motion." data-term-url="/en/glossary/view/mechanical/8516">mechanical</mark> hygrometers still usable at temperatures below freezing, as all other hygrometers respond much too slowly at low temperatures to be useful.</mark></p> <p>However, the amount of water vapor in the air is not an <mark class="term" data-term="independent variable" data-term-def="In science, an independent variable is a condition or parameter that is consciously manipulated in some way in the course of&hellip;" data-term-url="/en/glossary/view/independent+variable/3798">independent variable</mark>. If you live in a place with cold winters, you might have noticed that your hair and skin are drier in the winter. That’s partly because the air is drier: The amount of moisture that air can contain is directly related to the air temperature, and warmer air can contain more water vapor than colder air.</p> <p><mark id="ngss-606" class="ngss">In <mark class="term" data-term="meteorology" data-term-def="The scientific study of the atmosphere including the processes that cause particular weather conditions." data-term-url="/en/glossary/view/meteorology/11227">meteorology</mark>, <mark class="term" data-term="saturation" data-term-def="the state at which a body or parcel of air has reached its maximum capacity for holding dissolved moisture as water vapor." data-term-url="/en/glossary/view/saturation/12936">saturation</mark> is the state of the atmosphere in which air contains the maximum amount of water vapor that it can exist at a specific temperature and air pressure. Saturation is the principle that underlies the concept of <mark class="term" data-term="relative humidity" data-term-def="expressed as a percentage, this is the amount of water vapor present in the air when compared with the amount needed&hellip;" data-term-url="/en/glossary/view/relative+humidity/12935">relative humidity</mark>, which measures how close the air is to saturation with water vapor at a specific temperature and pressure. Whereas <mark class="term" data-term="absolute humidity" data-term-def="a measure of the amount of water vapor or moisture in the air, regardless of the air’s temperature. It is typically&hellip;" data-term-url="/en/glossary/view/absolute+humidity/12923">absolute humidity</mark> is a measure of the actual amount of water vapor in the air, regardless of the air’s temperature, relative humidity is expressed as a percentage and changes as air temperature changes. For example, on a typical spring day in the northern part of the United States, when a nighttime low of 45° F is reached, the relative humidity is close to 100% and there may be dew or frost on the ground by morning. As the day warms to a high of 70° F, the relative humidity decreases to around 45%.</mark></p> <p><mark id="ngss-623" class="ngss">Relative humidity is measured by taking advantage of the <mark class="term" data-term="process" data-term-def="Method, procedure; series of actions or steps." data-term-url="/en/glossary/view/process/8256">process</mark> of <mark class="term" data-term="evaporation" data-term-def="a change in the state of matter from the liquid phase (water) into the gas phase (water vapor)." data-term-url="/en/glossary/view/evaporation/12928">evaporation</mark> with a pair of calibrated thermometers (Figure 5). The first is a regular thermometer with a dry bulb that measures the air temperature. The second thermometer has a wet cloth on the bulb, which stays damp through a wicking mechanism. In an <mark class="term" data-term="environment" data-term-def="The conditions that surround and affect an organism." data-term-url="/en/glossary/view/environment/8270">environment</mark> like a desert, most moisture is quickly evaporated due to the warm, dry air, few clouds and low humidity, which encourages evaporation. Water evaporating from the wick into the air uses <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> and lowers the thermometer's temperature. With greater evaporation, the difference in temperature between these two thermometers is greater, and the relative humidity is lower. As the air nears saturation, evaporation decreases. If the air is fully saturated, no water can evaporate from the wet bulb, and the temperature readings will be the same. In this case, the relative humidity is 100%. Modern wet-dry bulb hygrometers typically have tables associated with them that allow for easy relative humidity calculations (Figure 5).</mark></p>  <div class="figure"> <figure> <button class="lightbox-button" data-lightbox-src="/img/library/large_images/image_12913.jpeg" data-lightbox="image"> <img src="/img/library/modules/mid289/Image/VLObject12913-23080801082257.jpeg" alt="Figure 5: A wet-dry bulb hygrometer with a table. " /> </button> <figcaption> <p><strong>Figure 5:</strong> A wet-dry bulb hygrometer with a table. </p> <span class="credit">image ©Creative Commons CC-BY</span> </figcaption> </figure> </div> <p>Understanding and measuring <mark class="term" data-term="relative humidity" data-term-def="expressed as a percentage, this is the amount of water vapor present in the air when compared with the amount needed&hellip;" data-term-url="/en/glossary/view/relative+humidity/12935">relative humidity</mark> was an important step in weather forecasting. Modern versions of these early instruments are still used in weather stations around the world. In the United States, many stations are operated by the National Weather Service, and the <mark class="term" data-term="data" data-term-def="(plural form of <b>datum</b>) A collection of pieces of information, generally taking the form of numbers, text, bits, or facts, that&hellip;" data-term-url="/en/glossary/view/data/3729">data</mark> they collect are used as input for local and regional forecasting <mark class="term" data-term="model" data-term-def="A representation, pattern, or mathematical description that can help scientists replicate a system." data-term-url="/en/glossary/view/model/8236">models</mark>.</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form name="cc12876"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">Water vapor in the air is measured ______.</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-12876-0-option-a" name="quiz-option-12876" type="radio" value="indirectly" > <span class="option__label"> <span class="screen-reader-only">a.</span> indirectly </span> </label> <span class="quiz__response" id="response-12876-0"> <strong>Correct!</strong> </span> </div> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-12876-1-option-b" name="quiz-option-12876" type="radio" value="directly" > <span class="option__label"> <span class="screen-reader-only">b.</span> directly </span> </label> <span class="quiz__response" id="response-12876-1"> <strong>Incorrect.</strong> </span> </div> </div> </div> </div> </form> </div> <div class="container margin-y-4 text-align-center"> <script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-9561344156007092" crossorigin="anonymous"></script>  <ins class="adsbygoogle" style="display:inline-block;width:300px;height:250px" data-ad-client="ca-pub-9561344156007092" data-ad-slot="3321739899"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> </div> </section> <section id="toc_4"> <h2>How water gets into the atmosphere</h2><p><mark id="ngss-607" class="ngss">Although water vapor is everywhere in Earth’s <mark class="term" data-term="atmosphere" data-term-def="The collective mass of gases that surrounds the Earth or another planet." data-term-url="/en/glossary/view/atmosphere/8529">atmosphere</mark>, the amount varies over time and space. One important factor is the <mark class="term" data-term="evaporation" data-term-def="a change in the state of matter from the liquid phase (water) into the gas phase (water vapor)." data-term-url="/en/glossary/view/evaporation/12928">evaporation</mark> rate or the extent to which water vapor gets into the atmosphere through the evaporation of <mark class="term" data-term="liquid" data-term-def="The state of matter characterized by its condensed nature and ability to flow. Unlike gases, molecules within a liquid often experience&hellip;" data-term-url="/en/glossary/view/liquid/8727">liquid</mark> water from Earth’s <mark class="term" data-term="surface" data-term-def="The outside or external part; the topside face of something." data-term-url="/en/glossary/view/surface/8275">surface</mark>. In evaporation, water undergoes a phase change from the lower-energy liquid phase to the higher-energy <mark class="term" data-term="gas" data-term-def="The state of matter characterized by its non-condensed nature and ability to flow. Unlike liquids, molecules within a gas remain far&hellip;" data-term-url="/en/glossary/view/gas/8725">gas</mark> phase, requiring an input of <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark>. On most of Earth’s surface, the energy source for evaporation is the sun: When sunlight warms the water, the <mark class="term" data-term="heat" data-term-def="A measure of the total internal energy of a substance that can be increased or decreased when objects with different temperatures&hellip;" data-term-url="/en/glossary/view/heat/1506">heat</mark> energy excites the water <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecules</mark>, and they move faster and faster until they move so fast that they escape as a gas. The warmer the water is, the greater the evaporation rate.</mark></p> <p><mark id="ngss-608" class="ngss">The sun is also warming the air. As the air temperature increases, its <mark class="term" data-term="saturation" data-term-def="the state at which a body or parcel of air has reached its maximum capacity for holding dissolved moisture as water vapor." data-term-url="/en/glossary/view/saturation/12936">saturation</mark> point increases and more water vapor can exist in the air. So, the warmer the air above the water, the greater the evaporation rate. If the air and water on Earth did not move, the evaporation <mark class="term" data-term="process" data-term-def="Method, procedure; series of actions or steps." data-term-url="/en/glossary/view/process/8256">process</mark> would be controlled almost entirely by daily temperature changes. However, both the atmosphere and the ocean are characterized by movement. <mark class="term" data-term="circulation" data-term-def="Generally, movement within a system. 1. [Atmospheric] the movement of air masses within the troposphere, driven by the redistribution of energy&hellip;" data-term-url="/en/glossary/view/circulation/10355">Circulation</mark> in the atmosphere produces winds on the ocean’s surface (see our <a href="https://www.visionlearning.com/en/library/Earth-Science/6/Factors-that-Control-Regional-Climate/255">Factors that <mark class="term" data-term="control" data-term-def="In science, a control is a system for which the expected change or outcome is well known and is measured or&hellip;" data-term-url="/en/glossary/view/control/3801">Control</mark> Regional Climate</a> module), and circulation in the ocean produces <mark class="term" data-term="current" data-term-def="a flow, as of electricity or water. In oceanography and hydrology, a channel of water that flows together at the same velocity" data-term-url="/en/glossary/view/current/8278">currents</mark> (see our <a href="https://www.visionlearning.com/en/library/Earth-Science/6/Ocean-Currents/282">Ocean Currents</a> module). The presence of wind <mark class="term" data-term="mean" data-term-def="In statistics, mean commonly refers to the arithmetic mean, also called the average, which is one measure of the mid-point of&hellip;" data-term-url="/en/glossary/view/mean/4221">means</mark> that a parcel of air (defined as a local <mark class="term" data-term="mass" data-term-def="A fundamental property of matter which is a numerical measure of the inertia of an object or the amount of matter&hellip;" data-term-url="/en/glossary/view/mass/3417">mass</mark> of air with temperature and/or moisture characteristics that are different from the surrounding air) saturated with water vapor will be moved out, leaving “space” for unsaturated air to move in, thus allowing more evaporation to occur. Ocean currents mean that waters of different temperatures can be brought in and change the evaporation rates accordingly.</mark></p> <p><mark id="ngss-609" class="ngss">Putting together all these factors, we can predict where evaporation rates are very high and very low. Evaporation is greatest where there is a large expanse of warm water with warm air temperatures and a <mark class="term" data-term="constant" data-term-def="In mathematics, a quantity that has a fixed value; something that does not vary." data-term-url="/en/glossary/view/constant/8557">constant</mark> wind that brings in unsaturated air. A good example of this is the lower <mark class="term" data-term="latitude" data-term-def="the angular distance of a place north or south of the Earth’s equator, expressed in degrees, minutes and seconds." data-term-url="/en/glossary/view/latitude/12930">latitudes</mark> of the Pacific Ocean, where <mark class="term" data-term="trade wind" data-term-def="a wind blowing steadily towards the equator from the northeast in the Northern Hemisphere and southeast in the Southern Hemisphere." data-term-url="/en/glossary/view/trade+wind/12937">trade winds</mark>, or, winds coming from the northeast and flowing towards the equator blow steadily over thousands of miles of open ocean warmed by the tropical sun (Figure 6). For that reason, the air that arrives on the east coast of the Big Island of Hawaii, where Hilo is located, is warm and fully saturated. In contrast, evaporation rates are low where there are cold water and cold air temperatures, like the Bering Sea in the northern Pacific Ocean (Figure 6). Since the air at high latitudes is so cold, it will have very little water vapor in it, so less evaporation can occur there.</mark></p>  <div class="figure"> <figure> <button class="lightbox-button" data-lightbox-src="/img/library/large_images/image_12914.png" data-lightbox="image"> <img src="/img/library/modules/mid289/Image/VLObject12914-23080801082457.png" alt="Figure 6: Map of the Pacific Ocean. The colors represent sea-surface temperature, with warmer temperatures in reds and cooler temperatures in blue. Curved white lines represent wind speed and direction." /> </button> <figcaption> <p><strong>Figure 6:</strong> Map of the Pacific Ocean. The colors represent sea-surface temperature, with warmer temperatures in reds and cooler temperatures in blue. Curved white lines represent wind speed and direction.</p> <span class="credit">image ©<a href="earth.nullschool.net"> Image derived from earth.nullschool.net. </a> </span> </figcaption> </figure> </div> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form name="cc12880"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">Warmer air can contain more water vapor because it has a ______.</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-12880-0-option-a" name="quiz-option-12880" type="radio" value="lower saturation point" > <span class="option__label"> <span class="screen-reader-only">a.</span> lower saturation point </span> </label> <span class="quiz__response" id="response-12880-0"> <strong>Incorrect.</strong> </span> </div> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-12880-1-option-b" name="quiz-option-12880" type="radio" value="higher saturation point" > <span class="option__label"> <span class="screen-reader-only">b.</span> higher saturation point </span> </label> <span class="quiz__response" id="response-12880-1"> <strong>Correct!</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_5"> <h2>How water vapor condenses in the atmosphere</h2><p><mark id="ngss-610" class="ngss">That warm, fully saturated air that arrives at Hilo with a <mark class="term" data-term="relative humidity" data-term-def="expressed as a percentage, this is the amount of water vapor present in the air when compared with the amount needed&hellip;" data-term-url="/en/glossary/view/relative+humidity/12935">relative humidity</mark> of 100% does not yet contain <mark class="term" data-term="liquid" data-term-def="The state of matter characterized by its condensed nature and ability to flow. Unlike gases, molecules within a liquid often experience&hellip;" data-term-url="/en/glossary/view/liquid/8727">liquid</mark> water. As long as the air temperature remains the same, water vapor will not condense to a liquid. For clouds to form and rain to start falling in Hilo, these factors—air temperature and capacity—must change.</mark></p> <p><mark id="ngss-611" class="ngss">If you look up at a cloud-free sky, it may appear empty. However, near-invisible sub-microscopic water droplets abound. The drops may start to clump together due to random collisions in the air, but if <mark class="term" data-term="evaporation" data-term-def="a change in the state of matter from the liquid phase (water) into the gas phase (water vapor)." data-term-url="/en/glossary/view/evaporation/12928">evaporation</mark> outpaces <mark class="term" data-term="condensation" data-term-def="The process of forming a liquid from a gas." data-term-url="/en/glossary/view/condensation/8561">condensation</mark>, the droplets will not survive long. If the air cools, the <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecules</mark> become less energetic, and the evaporation rate decreases. When there is more condensation than evaporation, liquid water droplets or ice <mark class="term" data-term="crystal" data-term-def="A solid of defined shape that is bound by plane surfaces (facets) that intersect at characteristic angles. The shape of a&hellip;" data-term-url="/en/glossary/view/crystal/1564">crystals</mark> can persist and can start to form clouds. The temperature at which this happens varies based on the relative humidity and is called the <mark class="term" data-term="dew point" data-term-def="the atmospheric temperature below which water droplets condense, forming dew or frost." data-term-url="/en/glossary/view/dew+point/12927">dew point</mark>.</mark></p> <p>How do air masses cool and reach their dew point? One way is through lifting due to the terrain. As the sun warms the air at the <mark class="term" data-term="surface" data-term-def="The outside or external part; the topside face of something." data-term-url="/en/glossary/view/surface/8275">surface</mark>, the air expands and becomes lighter, rising through the <mark class="term" data-term="atmosphere" data-term-def="The collective mass of gases that surrounds the Earth or another planet." data-term-url="/en/glossary/view/atmosphere/8529">atmosphere</mark>. The expansion causes the air temperature to decrease (see the Ideal <mark class="term" data-term="gas" data-term-def="The state of matter characterized by its non-condensed nature and ability to flow. Unlike liquids, molecules within a gas remain far&hellip;" data-term-url="/en/glossary/view/gas/8725">Gas</mark> <mark class="term" data-term="law" data-term-def="In science, a principle that describes a phenomenon, often mathematically." data-term-url="/en/glossary/view/law/8686">Law</mark> in our <a href="https://www.visionlearning.com/en/library/Chemistry/1/Properties-of-Gases/245">Properties of Gases</a> module).</p> <p>Still, water droplets and ice crystals don’t spontaneously form, even as the air cools. They need seed <mark class="term" data-term="particle" data-term-def="A tiny piece of matter." data-term-url="/en/glossary/view/particle/8259">particles</mark> to collect on—those particles could be dust, <mark class="term" data-term="salt" data-term-def="Generally, any ionic compound except those that contain hydroxide or hydrogen ions. Specifically, any compound other than water formed by&hellip;" data-term-url="/en/glossary/view/salt/1575">salt</mark> spray from the ocean, or aerosols, and, collectively, are called <mark class="term" data-term="cloud condensation nuclei" data-term-def="also called “cloud seeds”, these are small particles, typically one hundredth the size of a cloud droplet, on which water vapor&hellip;" data-term-url="/en/glossary/view/cloud+condensation+nuclei/12926">cloud condensation nuclei</mark> (CCN). When warm, saturated air rises and cools below its dew point with CCNs present, water vapor will condense, and clouds will form. So: How does the air near Hilo reach its dew point temperature and start to form clouds?</p> <p><mark id="ngss-612" class="ngss">On Hawai’i, air masses coming off the Pacific are saturated with water vapor and laden with CCN, typically salt particles. Those air masses encounter two mountains that rise gradually to over 4000 m (over 13,000’) tall, and the air masses also rise as they move up the slopes (Figure 7). As they do so, the air expands and cools, and water vapor condenses and creates clouds and <mark class="term" data-term="precipitation" data-term-def="Water that falls from the atmosphere to the ground in any form, such as rain, snow, hail, or sleet." data-term-url="/en/glossary/view/precipitation/8562">precipitation</mark>. In Figure 7, you can see that the zone with the highest annual precipitation is slightly inland (and uphill) from Hilo, where the air has risen and cooled enough to reach its dew point.</mark></p>  <div class="figure"> <figure> <button class="lightbox-button" data-lightbox-src="/img/library/large_images/image_12915.jpg" data-lightbox="image"> <img src="/img/library/modules/mid289/Image/VLObject12915-23080801083058.jpeg" alt="Figure 7: Map of Hawai’i showing annual rainfall. Direction of the trade winds are noted. Graphs show annual rainfall and elevation along the profile line shown on the map. " /> </button> <figcaption> <p><strong>Figure 7:</strong> Map of Hawai’i showing annual rainfall. Direction of the trade winds are noted. Graphs show annual rainfall and elevation along the profile line shown on the map. </p> </figcaption> </figure> </div> <p><mark id="ngss-613" class="ngss">This cooling and expansion with rising air happens at a predictable rate, called the lapse rate, which varies based on the moisture content of the air. When unsaturated air rises, it cools at a rate of 1° C per 100 m of elevation. The lapse rate decreases as the amount of moisture increases to a low of 0.6° C per 100 m of elevation for saturated air. Since the air approaching Hilo is coming from over the Pacific Ocean and will be saturated, the lapse rate near Hilo is closer to the lower rate. The graph in Figure 7 has gray lines every 1000 m. As an air parcel rises past each line, its temperature decreases by approximately 6° C (0.6°/100 m * 1000 m).</mark></p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form name="cc12885"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">In order for clouds to form, air masses must ______.</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-12885-0-option-a" name="quiz-option-12885" type="radio" value="fall, warm, and reach their dew point temperatures" > <span class="option__label"> <span class="screen-reader-only">a.</span> fall, warm, and reach their dew point temperatures </span> </label> <span class="quiz__response" id="response-12885-0"> <strong>Incorrect.</strong> </span> </div> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-12885-1-option-b" name="quiz-option-12885" type="radio" value="rise, cool, and reach their dew point temperatures" > <span class="option__label"> <span class="screen-reader-only">b.</span> rise, cool, and reach their dew point temperatures </span> </label> <span class="quiz__response" id="response-12885-1"> <strong>Correct!</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_6"> <h2>The distribution of precipitation</h2><p><mark id="ngss-614" class="ngss">Warm, saturated air full of CCN, rising and cooling, explains the high annual rainfall in Hilo but does not answer why it is so dry in Kona. Look back again at the rainfall map and the graph in Figure 7. Notice that the region of low <mark class="term" data-term="precipitation" data-term-def="Water that falls from the atmosphere to the ground in any form, such as rain, snow, hail, or sleet." data-term-url="/en/glossary/view/precipitation/8562">precipitation</mark> includes the two mountains, Mauna Kea and Mauna Loa. The air <mark class="term" data-term="mass" data-term-def="A fundamental property of matter which is a numerical measure of the inertia of an object or the amount of matter&hellip;" data-term-url="/en/glossary/view/mass/3417">mass</mark> rises more than 4000 m from sea level to pass over the mountains, meaning its temperature cools by 25° C (80° F) or more. This is a large enough change to condense most of the water vapor and <mark class="term" data-term="precipitate" data-term-def="A solid or otherwise insoluble product that is formed by a chemical reaction occuring in a liquid solution." data-term-url="/en/glossary/view/precipitate/4889">precipitate</mark> water out of the clouds on the side facing the wind. But the air mass keeps moving southwestward. As It descends and sinks along the western slope of the mountains, now at the higher lapse rate of 1° C per 100 m, the air will compress and its temperature will increase. Thus, the air mass reaches Kona as a warm, relatively dry air mass (Figure 7), with a high capacity to <mark class="term" data-term="absorb" data-term-def="Take in or soak up (energy, liquids, or other substances), usually gradually, through a chemical or physical action." data-term-url="/en/glossary/view/absorb/11219">absorb</mark> water vapor, promoting <mark class="term" data-term="evaporation" data-term-def="a change in the state of matter from the liquid phase (water) into the gas phase (water vapor)." data-term-url="/en/glossary/view/evaporation/12928">evaporation</mark> and preventing <mark class="term" data-term="condensation" data-term-def="The process of forming a liquid from a gas." data-term-url="/en/glossary/view/condensation/8561">condensation</mark>.</mark></p> <p><mark id="ngss-615" class="ngss">This pattern of precipitation is called the <mark class="term" data-term="rainshadow" data-term-def="a region that receives little rainfall because it is sheltered from prevailing rain-bearing winds by mountain slopes." data-term-url="/en/glossary/view/rainshadow/12934">rainshadow</mark> effect. The rainshadow effect occurs in many places around the world where a mountain range is aligned perpendicular to the <mark class="term" data-term="prevailing wind" data-term-def="a wind from the direction that is strongest at a particular place or season" data-term-url="/en/glossary/view/prevailing+wind/12617">prevailing winds</mark> coming off the ocean. Kona sits in the rainshadow of Mauna Kea; the Atacama Desert of Chile is in the rainshadow of the Andes; and Death Valley in California is in the rainshadow of the Sierra Nevada Mountains. The rainshadow effect is often visible in satellite imagery because the amount of rain strongly influences vegetation that can grow. Figure 8 shows a satellite image of the Big Island. The deep green vegetation on the island’s east side indicates high rainfall, while a mostly unvegetated, brown and black <mark class="term" data-term="landscape" data-term-def="The natural scenery of a region; a collection of landforms in an area." data-term-url="/en/glossary/view/landscape/8559">landscape</mark> on the west side indicates the rainshadow.</mark></p>  <div class="figure"> <figure> <button class="lightbox-button" data-lightbox="image"> <img src="/img/library/modules/mid289/Image/VLObject12916-23080801083244.jpg" alt="Figure 8: Satellite image of Hawaii from Google Earth. " /> </button> <figcaption> <p><strong>Figure 8:</strong> Satellite image of Hawaii from Google Earth. </p> </figcaption> </figure> </div> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form name="cc12888"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">A rainshadow forms due to _______.</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-12888-0-option-a" name="quiz-option-12888" type="radio" value="descending air on a mountain slope, leading to warming and prevention of condensation" > <span class="option__label"> <span class="screen-reader-only">a.</span> descending air on a mountain slope, leading to warming and prevention of condensation </span> </label> <span class="quiz__response" id="response-12888-0"> <strong>Correct!</strong> </span> </div> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-12888-1-option-b" name="quiz-option-12888" type="radio" value="ascending air on a mountain slope, leading to cooling and condensation" > <span class="option__label"> <span class="screen-reader-only">b.</span> ascending air on a mountain slope, leading to cooling and condensation </span> </label> <span class="quiz__response" id="response-12888-1"> <strong>Incorrect.</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_7"> <h2>Measuring and influencing water in the atmosphere</h2><p><mark id="ngss-616" class="ngss">Scientists still use thermometers and <mark class="term" data-term="hygrometer" data-term-def="an instrument capable of measuring the relative humidity of the air, or extent to which the air is saturated." data-term-url="/en/glossary/view/hygrometer/12929">hygrometers</mark> to make measurements at tens of thousands of weather <mark class="term" data-term="observation" data-term-def="1. The act of noticing something. 2. A record of that which has been noticed." data-term-url="/en/glossary/view/observation/8255">observation</mark> stations on the ground. Other ground-based instruments provide a bigger picture. For example, Doppler <mark class="term" data-term="radar" data-term-def="a system for detecting the presence of objects, like raindrops, by sending out pulses of high-frequency electromagnetic waves that are reflected&hellip;" data-term-url="/en/glossary/view/radar/12931">radar</mark> is a ground-based <mark class="term" data-term="system" data-term-def="A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for&hellip;" data-term-url="/en/glossary/view/system/3904">system</mark> that can detect most <mark class="term" data-term="precipitation" data-term-def="Water that falls from the atmosphere to the ground in any form, such as rain, snow, hail, or sleet." data-term-url="/en/glossary/view/precipitation/8562">precipitation</mark> within 145 km (90 miles) of the radar antenna, with heavy rain or snow detection within approximately 250 km (155 miles). However, other technologies are needed to get measurements vertically through the <mark class="term" data-term="atmosphere" data-term-def="The collective mass of gases that surrounds the Earth or another planet." data-term-url="/en/glossary/view/atmosphere/8529">atmosphere</mark> and across the globe.</mark></p> <p>Since around 1900, scientists have used weather balloons to <mark class="term" data-term="record" data-term-def="A written account or description. <br> <b>[verb]</b> To write an account or description." data-term-url="/en/glossary/view/record/8239">record</mark> temperature, pressure, and humidity vertically through the atmosphere. The National Weather Service launches modern weather balloons daily from 120 sites in the US; globally, there are 900 locations. The balloons are equipped with <mark class="term" data-term="radiosonde" data-term-def="an instrument package carried by a weather balloon to various levels of the atmosphere. It transmits information like air temperature, pressure&hellip;" data-term-url="/en/glossary/view/radiosonde/12932">radiosondes</mark>, instruments that transmit <mark class="term" data-term="data" data-term-def="(plural form of <b>datum</b>) A collection of pieces of information, generally taking the form of numbers, text, bits, or facts, that&hellip;" data-term-url="/en/glossary/view/data/3729">data</mark> back to ground-based stations. They rise at approximately 300 m per minute (1,000 feet/minute), transmitting their position, temperature, <mark class="term" data-term="relative humidity" data-term-def="expressed as a percentage, this is the amount of water vapor present in the air when compared with the amount needed&hellip;" data-term-url="/en/glossary/view/relative+humidity/12935">relative humidity</mark>, and air pressure every second or two. From this information, the wind speed and direction can also be calculated. Once the balloons reach an altitude of about 35 km (>20 miles), they burst, and the radiosondes fall back to the <mark class="term" data-term="surface" data-term-def="The outside or external part; the topside face of something." data-term-url="/en/glossary/view/surface/8275">surface</mark>, slowed by small parachutes.</p> <p><mark id="ngss-617" class="ngss">The launch of weather satellites, starting in the 1960s, expanded our ability to collect global data. Satellites can collect data to determine moisture and clouds in the atmosphere globally, enabling meteorologists to predict storm systems better. The data also allows for long-term studies showing how weather systems change over time under various influences.</mark></p> <p>Large-scale features of the planet primarily <mark class="term" data-term="control" data-term-def="In science, a control is a system for which the expected change or outcome is well known and is measured or&hellip;" data-term-url="/en/glossary/view/control/3801">control</mark> the patterns we observe in relative humidity, <mark class="term" data-term="evaporation" data-term-def="a change in the state of matter from the liquid phase (water) into the gas phase (water vapor)." data-term-url="/en/glossary/view/evaporation/12928">evaporation</mark>, and precipitation (like the <mark class="term" data-term="rainshadow" data-term-def="a region that receives little rainfall because it is sheltered from prevailing rain-bearing winds by mountain slopes." data-term-url="/en/glossary/view/rainshadow/12934">rainshadow</mark> effect). Those large-scale features are the incoming <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> from the sun, <mark class="term" data-term="circulation" data-term-def="Generally, movement within a system. 1. [Atmospheric] the movement of air masses within the troposphere, driven by the redistribution of energy&hellip;" data-term-url="/en/glossary/view/circulation/10355">circulation</mark> in the atmosphere, and the distribution of oceans and mountain ranges. However, humans also influence the distribution of water in the atmosphere.</p></section> <section id="toc_8"> <h2>The human influence</h2><p>Around 2000, meteorologist J. Marshall Shepherd was a <mark class="term" data-term="research" data-term-def="A study or an investigation." data-term-url="/en/glossary/view/research/8257">research</mark> scientist at the <mark class="term" data-term="NASA" data-term-def="The National Aeronautics and Space Administration, a US government office established in 1958 to research flight in the Earth's atmosphere and beyond." data-term-url="/en/glossary/view/NASA/5494">NASA</mark> Goddard Space Flight Center. During this time, he became interested in using space-based <mark class="term" data-term="method" data-term-def="A procedure or process; a systematic way of performing a task or conducting research." data-term-url="/en/glossary/view/method/8238">methods</mark> to demonstrate the impact of urban <mark class="term" data-term="environment" data-term-def="The conditions that surround and affect an organism." data-term-url="/en/glossary/view/environment/8270">environments</mark> on <mark class="term" data-term="precipitation" data-term-def="Water that falls from the atmosphere to the ground in any form, such as rain, snow, hail, or sleet." data-term-url="/en/glossary/view/precipitation/8562">precipitation</mark>. <mark id="ngss-618" class="ngss">Shepherd knew that ground-based measurements revealed an “urban heat-island effect,” in which replacing <mark class="term" data-term="soil" data-term-def="The loose top layer of Earth’s surface where plants grow, made up of particles of rocks, minerals, and organic material." data-term-url="/en/glossary/view/soil/8563">soil</mark> and vegetation with the asphalt and concrete of cities leads to an increase in air temperature and <mark class="term" data-term="evaporation" data-term-def="a change in the state of matter from the liquid phase (water) into the gas phase (water vapor)." data-term-url="/en/glossary/view/evaporation/12928">evaporation</mark> that influences precipitation downwind of the city.</mark> But these studies relied on volunteers and ground-based measurements, so their findings were limited to a few urban areas.</p> <p><mark id="ngss-619" class="ngss">Shepherd used the precipitation <mark class="term" data-term="radar" data-term-def="a system for detecting the presence of objects, like raindrops, by sending out pulses of high-frequency electromagnetic waves that are reflected&hellip;" data-term-url="/en/glossary/view/radar/12931">radar</mark> collected with the Tropical Rainfall Measuring Mission (TRMM) satellite from 1998 to 2000 to expand the <mark class="term" data-term="observation" data-term-def="1. The act of noticing something. 2. A record of that which has been noticed." data-term-url="/en/glossary/view/observation/8255">observations</mark> of precipitation around major cities in the southeastern United States. These cities included Atlanta, GA, Nashville, TN, and three cities in Texas: Dallas, San Antonio, and Waco. In analyzing the satellite <mark class="term" data-term="data" data-term-def="(plural form of <b>datum</b>) A collection of pieces of information, generally taking the form of numbers, text, bits, or facts, that&hellip;" data-term-url="/en/glossary/view/data/3729">data</mark>, he determined that the region downwind of these cities experienced an <mark class="term" data-term="average" data-term-def="In statistics, average commonly refers to the arithmetic mean, also called simply "mean," which is one measure of the mid-point of&hellip;" data-term-url="/en/glossary/view/average/8542">average</mark> 28% increase in precipitation compared to upwind areas (Shepherd et al., 2002). The warm air generated by the urban environment caused greater evaporation, rising and cooling, and <mark class="term" data-term="condensation" data-term-def="The process of forming a liquid from a gas." data-term-url="/en/glossary/view/condensation/8561">condensation</mark> as it moved away from the city. In Atlanta, Shepherd even determined that the number of rain delays had increased at the baseball stadium, thanks to this phenomenon!</mark></p> <p>Shepherd then sought to correlate the satellite data with ground-based measurements to extend his findings back in time. He examined a <mark class="term" data-term="rain gauge" data-term-def="a device for collecting and measuring the amount of falling precipitation." data-term-url="/en/glossary/view/rain+gauge/12933">rain gauge</mark> <mark class="term" data-term="record" data-term-def="A written account or description. <br> <b>[verb]</b> To write an account or description." data-term-url="/en/glossary/view/record/8239">record</mark> that began in the late 1890s in Phoenix, AZ, which is located in a very dry climatic zone. <mark id="ngss-620" class="ngss">The record revealed that increases in the amount and <mark class="term" data-term="frequency" data-term-def="The rate at which a vibration occurs that constitutes a wave, either in a material or in an electromagnetic field, usually&hellip;" data-term-url="/en/glossary/view/frequency/2210">frequency</mark> of precipitation only appeared after urbanization, starting in about 1950 (Shepherd, 2006). As the <mark class="term" data-term="evidence" data-term-def="Support for an idea, opinion, or hypothesis." data-term-url="/en/glossary/view/evidence/8243">evidence</mark> for the influence of urban centers on precipitation accumulated, Shepherd began to address the implications and potential hazards, including flooding (KC et al., 2015).</mark> Many communities are unprepared for these relatively rapid changes in climatic conditions. For instance, a city like Hilo, Hawaii, which experiences high yearly rainfall, is prepared to deal with runoff. However, cities downwind of Phoenix, AZ, have not had time to adapt to high rainfall and are more likely to be impacted by flooding.</p> <p>Likewise, <mark id="ngss-621" class="ngss">Earth’s warming <mark class="term" data-term="climate" data-term-def="Climate describes the average and patterns of a particular area’s weather over time. Climate includes such elements as temperature, precipitation, humidity,&hellip;" data-term-url="/en/glossary/view/climate/9334">climate</mark> is leading to global-scale changes in water distribution in the <mark class="term" data-term="atmosphere" data-term-def="The collective mass of gases that surrounds the Earth or another planet." data-term-url="/en/glossary/view/atmosphere/8529">atmosphere</mark>. Temperature and precipitation characteristics of a region change as regional <mark class="term" data-term="climatic zones" data-term-def="areas characterized by distinct climates that correspond either with weather patterns, latitude, or communities of plants and animals." data-term-url="/en/glossary/view/climatic+zones/12925">climatic zones</mark> shift in response to global temperature changes (see our <a href="https://www.visionlearning.com/en/library/Earth-Science/6/Factors-that-Control-Regional-Climate/255">Factors that Influence Regional Climate</a> module). Places like Hawaii, in the middle of the Pacific Ocean and the zone of <mark class="term" data-term="trade wind" data-term-def="a wind blowing steadily towards the equator from the northeast in the Northern Hemisphere and southeast in the Southern Hemisphere." data-term-url="/en/glossary/view/trade+wind/12937">trade winds</mark>, will experience change more slowly than places on the margins of climatic zones and on large landmasses, like Phoenix and other inland cities.</mark></p> <p>In all cases, <mark id="ngss-622" class="ngss">the regular measurements we take at the <mark class="term" data-term="surface" data-term-def="The outside or external part; the topside face of something." data-term-url="/en/glossary/view/surface/8275">surface</mark>, throughout the atmosphere, and from satellites can help us forecast the impacts of water in the atmosphere in the short term and help us identify long-term trends to make predictions about the future. Short-term forecasts and long-term trends help decide everything from whether to carry an umbrella to which crops to plant to how to build structures to withstand extreme floods.</mark></p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form name="cc12893"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">True or False: Human activity has no effect on the distribution of water in the atmosphere.</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-12893-0-option-a" name="quiz-option-12893" type="radio" value="True" > <span class="option__label"> <span class="screen-reader-only">a.</span> True </span> </label> <span class="quiz__response" id="response-12893-0"> <strong>Incorrect.</strong> </span> </div> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-12893-1-option-b" name="quiz-option-12893" type="radio" value="False" > <span class="option__label"> <span class="screen-reader-only">b.</span> False </span> </label> <span class="quiz__response" id="response-12893-1"> <strong>Correct!</strong> </span> </div> </div> </div> </div> </form> </div> </section> <footer class="module__main__footer"> <hr class="border-color-dark"> <p class="citation"> <em> Anne E. Egger, Ph.D., Ulyana Horodyskyj Pena, Ph.D. “Water in the Atmosphere” Visionlearning Vol. EAS-3 (8), 2023. </em> </p>  <div class="title-list" id="refs" name="refs"> <p class="h6 title-list__title"> References </p> <ul class="title-list__list"> <li><p>Binita, K. C., Shepherd, J. M., & Gaither, C. J. (2015). Climate change vulnerability assessment in Georgia. <em>Applied Geography, 62,</em> 62-74.</p></li> <li><p>Giambelluca, T. W., Chen, Q., Frazier, A. G., Price, J. P., Chen, Y. L., Chu, P. S., ... & Delparte, D. M. (2013). Online rainfall atlas of Hawai ‘i. <em>Bulletin of the American Meteorological Society, 94</em>(3), 313-316./p></li> <li><p>Shepherd, J. M. (2006). Evidence of urban-induced precipitation variability in arid climate regimes. <em>Journal of Arid Environments, 67</em>(4), 607-628.</p></li> <li><p>Shepherd, J. M., Pierce, H., & Negri, A. J. (2002). Rainfall modification by major urban areas: Observations from spaceborne rain radar on the TRMM satellite. <em>Journal of Applied Meteorology and Climatology, 41</em>(7), 689-701.</p></li> </ul> </div> </footer> </div>    </article> </div> </div> </main> <script id="ngssCommentdata" type="application/json"> [{"ngss_tag_id":null,"type":"p","tag":"","name":null,"description":null,"comment":"<p>The process of asking questions assists in answering questions related to a phenomena.<\/p>\r\n\r\n<p><strong>HS-SEP.1 Asking Questions and Defining Problems:<\/strong> Ask questions that arise from careful observation of phenomena, or unexpected results, to clarify and\/or seek additional information.<\/p>","is_public":"1","mod_ngss_comment_id":"599","display_order":"1","dimension":"p","dimension_full":"Science and Engineering Practices"},{"ngss_tag_id":null,"type":"dci","tag":"","name":null,"description":null,"comment":"<p>Humans rely on natural resources.<\/p>\r\n\r\n<p><strong>HS-ESS3.A Natural Resources:<\/strong>\r\nResource availability has guided the development of human society.<\/p>","is_public":"1","mod_ngss_comment_id":"600","display_order":"2","dimension":"dci","dimension_full":"Disciplinary Core Ideas"},{"ngss_tag_id":null,"type":"p","tag":"","name":null,"description":null,"comment":"<p>Rain gauges are used to monitor rainfall amounts.<\/p>\r\n\r\n<p><strong>SEP.2 Planning and Carrying Out Investigations:<\/strong> Select appropriate tools to collect, record, analyze, and evaluate data.<\/p>","is_public":"1","mod_ngss_comment_id":"601","display_order":"3","dimension":"p","dimension_full":"Science and Engineering Practices"},{"ngss_tag_id":null,"type":"p","tag":"","name":null,"description":null,"comment":"<p>Rain gauges are used to monitor rainfall amounts.<\/p>\r\n\r\n<p><strong>SEP.2 Planning and Carrying Out Investigations:<\/strong> Select appropriate tools to collect, record, analyze, and evaluate data.<\/p>","is_public":"1","mod_ngss_comment_id":"602","display_order":"4","dimension":"p","dimension_full":"Science and Engineering Practices"},{"ngss_tag_id":null,"type":"dci","tag":"","name":null,"description":null,"comment":"<p>An understanding the properties of water is needed to understand and measure moisture in the atmosphere.<\/p>\r\n\r\n<p><strong>HS-ESS2.C The Roles on Water in Earth's Surface Processes:<\/strong> The abundance of liquid water on Earth\u2019s surface and its unique combination of physical and chemical properties are central to the planet\u2019s dynamics. 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Water in the Atmosphere | Earth Science | Visionlearning