{"id":179011,"date":"2012-06-19T23:24:18","date_gmt":"2012-06-20T06:24:18","guid":{"rendered":"http:\/\/www.esri.com\/arcgis-blog\/?post_type=blog&p=179011"},"modified":"2018-12-18T10:32:33","modified_gmt":"2018-12-18T18:32:33","slug":"world-average-annual-evapotranspiration-web-map-now-available","status":"publish","type":"blog","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-online\/mapping\/world-average-annual-evapotranspiration-web-map-now-available","title":{"rendered":"World average annual evapotranspiration web map now available"},"author":5221,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","format":"standard","meta":{"_acf_changed":false,"_searchwp_excluded":""},"categories":[22941,23051],"tags":[24981],"industry":[],"product":[36551],"class_list":["post-179011","blog","type-blog","status-publish","format-standard","hentry","category-mapping","category-water","tag-hydro","product-arcgis-online"],"acf":{"short_description":"EvapotranspirationMost of us understand the hydrologic cycle in terms of the visible paths that water can take: rainstorms, rivers, waterfalls, ","flexible_content":[{"acf_fc_layout":"content","content":"

\"Evapotranspiration\"Most of us understand the hydrologic cycle in terms of the visible paths that water can take: rainstorms, rivers, waterfalls, swamps, etc.\u00a0\u00a0However, an even larger volume of water flows through the air all around us in two\u00a0invisible\u00a0paths: evaporation and transpiration. They claim 61% of all terrestrial precipitation, and together are referred to as evapotranpsiration.\u00a0In order to better understand this important process, Esri\u2019s Mapping Center has produced a web map showing the world\u2019s\u00a0average annual evapotranspiration<\/strong><\/a>.<\/p>\n

\"World<\/p>\n

This map was built using the\u00a0MOD16 Global Evapotranspiration Product<\/a><\/strong>, which is derived from satellite imagery by researchers at the University of Montana.\u00a0 The imagery is from the Moderate Resolution Imaging Spectroradiometer (MODIS), an instrument with 1-km resolution carried by two NASA satellites.\u00a0 The\u00a0MOD16 algorithm<\/a><\/strong>\u00a0derives from raw imagery a number of secondary data products like land surface temperature, leaf area index, and net solar radiation.\u00a0 These intermediate data are used to solve the\u00a0Penman-Monteith<\/a><\/strong>\u00a0equation for total daily evapotranspiration.\u00a0 MODIS was first launched aboard the Terra satellite in 2000, and the full 11-year evapotranspiration time series is available as\u00a08-day<\/a><\/strong>,\u00a0monthly<\/a><\/strong>, and\u00a0annual<\/a><\/strong>\u00a0averages.\u00a0 A\u00a0toolbox<\/strong><\/a>\u00a0for downloading monthly MODIS data is available in the ArcGIS Resource Center.\u00a0 We calculated the average annual evapotranspiration for the period of record, which we display along with an\u00a0elevation hillshade<\/a><\/strong>using the\u00a0No Alteration of Grayscale or Intensity<\/strong>\u00a0(NAGI<\/a><\/strong>) method.<\/p>\n

Click anywhere on the map, and a pop-up window shows evapotranspiration as a fraction of the evapotranspiration potential.\u00a0 For example,\u00a0Scotland and Norway have a lower rate of evapotranspiration than the Congo, despite\u00a0receiving\u00a0just as much rain, because\u00a0potential\u00a0evapotranspiration is lower, which means that there is not enough solar energy to vaporize all the water.\u00a0 The Sahara Desert has high potential evapotranspiration, but receives little rain, and the unused solar energy heats the sand to over 170 degrees Fahrenheit.\u00a0 In the Congo River Basin, there is high potential evapotranspiration and ample precipitation, so less of the potential goes unused.\u00a0 The result is a much cooler, more humid climate with abundant plant life.\u00a0 Also, look for irrigation projects, which show up as bright red splotches in otherwise barren regions.<\/p>\n

\"Nile<\/p>\n

If you want to use this map as a canvas for your own observational data, find it\u00a0here<\/a>. You can also access any of the individual services that make up the web map:<\/p>\n