Potential Evapotranspiration

<div style='margin: 0px; padding: 0px;'>The combined processes of evaporation and transpiration, known as evapotranspiration (ET), plays a key role in the <a href='https://en.wikipedia.org/wiki/Water_cycle' rel='nofollow ugc' target='_blank'>water cycle</a>.  Precipitation that falls on land can either run off in streams and rivers, soak into the ground, or return to the atmosphere through evapotranspiration. Water that evaporates returns directly to the atmosphere while water that is transpired is taken up by plant roots and lost to the atmosphere through the leaves.<br /></div><div style='margin: 0px; padding: 0px;'><br /></div><div style='margin: 0px; padding: 0px;'>Evapotranspiration data can be used to calculate regional water and energy balance and soil water status and provides key information for water resource management. Potential evapotranspiration, the amount of ET that would occur if soil moisture were not limited, is a purely meteorological characteristic, based on air temperature, solar radiation, and wind speed. <a href='https://www.arcgis.com/home/item.html?id=31f7c3727abf42249a43fe8f25470af4' rel='nofollow ugc' target='_blank'>Actual evapotranspiration</a> also depends on water availability, so it might occur at very close to the potential rate in a rainforest, but be much lower in a desert despite the higher potential there.</div><div style='margin: 0px; padding: 0px;'><br /></div><div style='text-align: center; margin: 0px; padding: 0px;'><font size='4'><b>Dataset Summary</b></font></div><div style='margin: 0px; padding: 0px;'><div style='margin: 0px; padding: 0px;'><b>Phenomenon Mapped:</b> Evapotranspiration<br /></div><div style='margin: 0px; padding: 0px;'><div><b>Units:</b> Millimeters per year</div><div><b>Cell Size:</b> 927.6623821756539  meters</div><div><b>Source Type:</b> Continuous</div><div><b>Pixel Type:</b> 16-bit unsigned integer</div><div><b>Data Coordinate System:</b> Web Mercator Auxiliary Sphere</div><div><b>Extent:</b> Global </div><div><b>Source:</b> University of Montana <span style='box-sizing: border-box; background-image: initial; background-position: 0px 0px; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; border-bottom-width: initial; border-bottom-color: initial; transition: all 0.4s ease-in-out; margin-top: auto; margin-right: 8px; margin-bottom: auto; text-shadow: rgb(255, 255, 255) 0px 1px 0px;'>Numerical Terradynamic Simulation Group</span></div><div><b>Publication Date:</b> March 10, 2015</div><div><b>ArcGIS Server URL:</b> https://landscape6.arcgis.com/arcgis/</div><div><br /></div><div><div style='margin: 0px; padding: 0px;'>This layer provides access to a 1km cell sized raster of average annual evaporative loss from the land surface, measured in mm/year. Data are from the <a href='https://www.ntsg.umt.edu/project/modis/mod16.php' rel='nofollow ugc' target='_blank'>MOD16 Global Evapotranspiration Product</a>, which is derived from MODIS imagery by a team of researchers at the University of Montana. This algorithm, which involves estimating land surface temperature and albedo and using them to solve the <a href='https://en.wikipedia.org/wiki/Penman%E2%80%93Monteith_equation' rel='nofollow ugc' target='_blank'>Penman-Monteith</a> equation, is not valid over urban or barren land so these are shown as NoData, as is any open water. For all other pixels, the algorithm was used to estimate evapotranspiration for every 8-day period from 2000 to 2014 and these estimates have been averaged together to come up with the annual normal. You can also get access to the monthly totals using the <a href='https://hydroteam.maps.arcgis.com/home/item.html?id=5fe74de4ec254bc09515e562abe994e1' rel='nofollow ugc' target='_blank'>MODIS Toolbox</a>.</div><div style='margin: 0px; padding: 0px;'><div style='margin: 0px; padding: 0px;'></div></div></div></div></div><div style='margin: 0px; padding: 0px;'><br /></div><div style='margin: 0px; padding: 0px;'><div style='margin: 0px; padding: 0px;'><div style='text-align: center; font-family: &quot;Avenir Next W01&quot;, &quot;Avenir Next W00&quot;, &quot;Avenir Next&quot;, Avenir, &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; font-size: 17px; background-color: rgb(255, 255, 255); margin: 0px; padding: 0px;'><b><font size='4'>What can you do with this Layer?</font> </b></div><div style='font-family: &quot;Avenir Next W01&quot;, &quot;Avenir Next W00&quot;, &quot;Avenir Next&quot;, Avenir, &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; font-size: 17px; background-color: rgb(255, 255, 255); margin: 0px; padding: 0px;'><div style='margin: 0px; padding: 0px;'>This layer is suitable for both visualization and analysis across the ArcGIS system. This layer can be combined with your data and other layers from the <a href='https://livingatlas.arcgis.com/' rel='nofollow ugc' style='color: rgb(0, 121, 193); text-decoration-line: none;' target='_blank'>ArcGIS Living Atlas of the World</a> in ArcGIS Online and ArcGIS Pro to create powerful web maps that can be used alone or in a story map or other application.</div><div style='margin: 0px; padding: 0px;'><br /></div><div style='margin: 0px; padding: 0px;'>Because this layer is part of the <a href='https://livingatlas.arcgis.com/' rel='nofollow ugc' style='color: rgb(0, 121, 193); text-decoration-line: none;' target='_blank'>ArcGIS Living Atlas of the World</a> it is easy to add to your map:</div><div style='margin: 0px; padding: 0px;'><ul><li>In ArcGIS Online, you can add this layer to a map by selecting <i>Add</i> then <i>Browse Living Atlas Layers</i>. A window will open. Type &quot;evapotranspiration&quot; in the search box and browse to the layer. Select the layer then click <i>Add to Map</i>.<br /></li><li>In ArcGIS Pro, open a map and select <i>Add Data</i> from the Map Tab. Select <i>Data</i> at the top of the drop down menu. The Add Data dialog box will open on the left side of the box, expand <i>Portal</i> if necessary, then select <i>Living Atlas</i>. Type &quot;evapotranspiration&quot; in the search box, browse to the layer then click OK.</li></ul></div><div style='margin: 0px; padding: 0px;'>In ArcGIS Pro you can use the built-in <a href='https://pro.arcgis.com/en/pro-app/help/data/imagery/raster-functions.htm' rel='nofollow ugc' style='color: rgb(0, 121, 193); text-decoration-line: none;' target='_blank'>raster functions</a> or create your own to create custom extracts of the data. Imagery layers provide fast, powerful inputs to geoprocessing tools, models, or Python scripts in Pro.</div><div style='margin: 0px; padding: 0px;'><br /></div><div style='margin: 0px; padding: 0px;'>The <a href='https://doc.arcgis.com/en/living-atlas/#s=0&amp;n=0&amp;d=1&amp;col=&amp;fs=0&amp;fn=30&amp;npp=120&amp;subCat=0' rel='nofollow ugc' style='color: rgb(0, 121, 193); text-decoration-line: none;' target='_blank'>ArcGIS Living Atlas of the World</a> provides an easy way to explore many other beautiful and authoritative maps on hundreds of topics like this one.</div></div></div></div>