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<!DOCTYPE HTML><html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html;charset=utf-8" /> <link rel="stylesheet" type="text/css" href="https://www.giss.nasa.gov/css/css2104.css" media="all" /> <title>Data.GISS: Global Aerosol Climatology Project</title> <link rel="apple-touch-icon" href="/gfx/apple-touch-icon-180x180.png" /> <link rel="apple-touch-icon-precomposed" href="/gfx/apple-touch-icon-180x180.png" /> <link rel="apple-touch-icon" sizes="192x192" href="/gfx/apple-touch-icon-192x192.png" /> <link rel="apple-touch-icon" sizes="180x180" href="/gfx/apple-touch-icon-180x180.png" /> <link rel="apple-touch-icon" sizes="152x152" href="/gfx/apple-touch-icon-152x152.png" /> <link rel="apple-touch-icon" sizes="128x128" href="/gfx/apple-touch-icon-128x128.png" /> <link rel="apple-touch-icon" sizes="76x76" href="/gfx/apple-touch-icon-76x76.png" /> <meta name="orgcode" content="611" /> <meta name="rno" content="Gavin.A.Schmidt.1" /> <meta name="content-owner" content="Robert.B.Schmunk.1" /> <meta name="webmaster" content="Robert.B.Schmunk.1" /> <meta name="viewport" content="width=956, initial-scale=1" /><script id="_fed_an_ua_tag" src="https://dap.digitalgov.gov/Universal-Federated-Analytics-Min.js?agency=NASA&subagency=GISS&yt=true&dclink=true" async="async"></script> </head> <body> <div id="bkg1"><div id="bkg2"></div></div> <div id="page"> <div id="archive"> <p>This page's content is no longer actively maintained, but the material has been kept on-line for historical purposes.<br />The page may contain broken links or outdated information, and parts may not function in current web browsers.</p></div> <div class="hidden"> <a href="#content" title="Go to Main Content" accesskey="2">Go to Main Content (Accesskey 2)</a><br /><a href="#nav" title="Go to Site Menu" accesskey="3">Go to Site Menu (Accesskey 3)</a></div> <div id="header"> <div id="headerlogo"> <a href="https://www.nasa.gov/"><img src="https://www.giss.nasa.gov/gfx/2013/nasa_x2.png" alt="NASA Logo, National Aeronautics and Space Administration" style="width:140px;height:98px" /></a></div> <div id="centername"> <h1><a href="https://www.nasa.gov/">National Aeronautics and Space Administration</a></h1> <h2><a href="https://www.giss.nasa.gov/">Goddard Institute for Space Studies</a></h2></div> <div id="hierarchy"> <h2><a href="https://www.nasa.gov/goddard/">Goddard Space Flight Center</a><br /><a href="https://science.gsfc.nasa.gov/sci">Sciences and Exploration Directorate</a><br /><a href="https://science.gsfc.nasa.gov/earth">Earth Sciences Division</a></h2></div></div> <div id="paper"> <div id="content"> <div id="cbanner" style="height:96px"> <h2><img src="gfx/gacp_1488x196.jpg" style="width:744px;height:96px" alt="Global Aerosol Climatology Project" /></h2> </div> <div id="cpad"> <div style="text-align:center;border:solid gray 1px;margin-bottom:12px;padding:0;background:#eee"> <p style="padding:2px;margin:0;font-weight:bold">GACP — <a href="/gacp/">Home</a> — <a href="/gacp/publications/">Publications</a> — <a href="/gacp/datasets/">Datasets</a> — <a href="/gacp/projects/">Projects</a> — <a href="/gacp/campaigns/">Field Campaigns</a> — <a href="/gacp/meeting/">Meetings</a> </p> </div> <div class="col1"> <p> Tropospheric aerosols are thought to cause a significant direct and indirect climate forcing, but the magnitude of this forcing remains highly uncertain because of poor knowledge of global aerosol characteristics and their temporal changes. The standard long-term global NOAA product, the one-channel AVHRR aerosol optical thickness over the ocean, relies on a single predefined aerosol model and can be inaccurate in many cases. TOMS data can be used to detect absorbing aerosols over land, but are insensitive to aerosols located below 1 km. It is thus clear that innovative approaches must be employed in order to extract a more quantitative and accurate aerosol climatology from available satellite and other measurements, thereby enabling more reliable estimates of the direct and indirect aerosol forcings. </p> <p> The Global Aerosol Climatology Project (GACP) was established in 1998 in response to the recommendations of the <a href="https://www.giss.nasa.gov/events/aerosols1997/">1997 Aerosol Workshop</a> held at the NASA <a href="https://www.giss.nasa.gov/">Goddard Institute for Space Studies</a> (GISS) and the resulting call for a focused effort aimed at extracting an improved multi-decadal aerosol record from existing satellite measurements as outlined in the Aerosol Radiative Forcing NRA. Specifically, the main objective has been to develop advanced global aerosol climatologies for the full period of satellite data, supplement them by improved modeling results, and to make these aerosol datasets broadly available and suitable for use in studies of the direct and indirect effects of aerosols on climate. </p> <p> The project was part of the NASA Radiation Sciences Program and the <a href="http://www.gewex.org/">Global Energy and Water Cycle Experiment</a> (GEWEX). Its main objectives were to: </p> <ol> <li>Analyze satellite radiance measurements and field observations in order to infer the global distribution of aerosols, their properties, and their seasonal and interannual variations; and </li> <li>Perform advanced global and regional modeling studies of the aerosol formation, processing, and transport.</li> </ol> <p> To accomplish these objectives, the Earth Science Enterprise (formerly called Mission to Planet Earth) of NASA Headquarters established a processing center at the Goddard Institute for Space Studies and issued a research announcement (NRA-97-MTPE-16). The principal investigators of the successful proposals formed the GACP Science Team. Besides pursuing their individual research objectives, the members of the Science Team have participated in selecting candidate algorithms to be applied to the full period of satellite measurements in order to estimate parameters of significance to the aerosol climatology. The processing center has been employing the algorithms recommended by the Science Team to produce the satellite element of the combined GACP aerosol product. </p> <p> In the framework of GACP, multichannel aerosol retrieval algorithms, as suggested or reviewed by the GACP Science Team, have been systematically applied to the full period of satellite measurements. The algorithms have been tested and refined using ground-based/in situ data and contemporaneous EOS results. The full period of available satellite data has been reprocessed as improved algorithms or data calibration were achieved. The satellite retrievals over oceans and limited surface measurements have been used to calibrate 3-D tracer aerosol models for individual aerosol types and sources. These calibrated tracer models have thus provided an alternative estimate of the aerosol distribution over continents. Still further refinements of the aerosol climatologies may be possible using TOMS and in situ/ground-based data. </p> <p> A major outcome of this collective research effort is a 23-year global aerosol climatology compiled from channel-1 and -2 AVHRR data and supplemented by data from other satellites, field observations, and chemical-transport modeling. The resulting datasets and analysis products have been documents in numerous peer-reviewed publications, including a special issue of the <cite>Journal of Atmospheric Sciences</cite>. They have been used to improve the understanding and modeling of the climate forcing due to changing aerosols, including both the direct radiative forcing by the aerosols and the indirect radiative forcing caused by the effects of changing aerosols on cloud properties. </p> <p> The results of this project have also been used in outreach programs, thus providing a mechanism to test the use of the aerosol research as a tool for teaching science. </p> </div> <div class="col2"> <h2>Contacts</h2> <p> <b>Hal Maring</b><br /> <i>Program Manager</i><br /> Radiation Sciences Program<br /> Sun-Earth System Division<br /> NASA Headquarters<br /> 300 E ST SW<br /> Washington DC 20546-0001 </p> <p> <b>Paul D. Try</b><br /> <i>Director</i><br /> <a href="http://www.gewex.org/contact/"> International GEWEX Project Office</a><br /> 1010 Wayne Ave.<br /> Suite 450<br /> Silver Spring, MD 20910 USA </p> <p> <b>Joyce E. Penner</b><br /> <i>Science Team Leader</i><br /> Dept. of Atmospheric, Oceanic and Space Sciences<br /> University of Michigan<br /> 2455 Hayward Street<br /> Ann Arbor, MI 48109-2143 </p> <p> <b>Michael Mishchenko</b><br /> <i>Project Manager</i><br /> NASA Goddard Institute for Space Studies<br /> 2880 Broadway<br /> New York, NY 10025 </p> </div> <div style="clear:both; margin-top:12px"></div> <div style="text-align:center;border:solid gray 1px;margin-bottom:12px;padding:0;background:#eee"> <p style="padding:2px;margin:0;font-weight:bold">GACP — <a href="/gacp/">Home</a> — <a href="/gacp/publications/">Publications</a> — <a href="/gacp/datasets/">Datasets</a> — <a href="/gacp/projects/">Projects</a> — <a href="/gacp/campaigns/">Field Campaigns</a> — <a href="/gacp/meeting/">Meetings</a> </p> </div> </div> </div> <div id="nav"><h3>Site Menu</h3> <ul id="mnav"> <li><a href="https://www.giss.nasa.gov/">GISS Home</a></li> <li><a href="https://www.giss.nasa.gov/research/">News & 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