Actual Evapotranspiration

Retirement Notice: This item is in mature support as of April 2024 and will be retired in December 2026. A new version of this item is available for your use. Esri recommends updating your maps and apps to use the new version. The combined processes of evaporation and transpiration, known as evapotranspiration (ET), plays a key role in the water cycle. 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. 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. Actual evapotranspiration 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. Dataset Summary Phenomenon Mapped: Evapotranspiration Units: Millimeters per year Cell Size: 927.6623821756539 meters Source Type: Continuous Pixel Type: 16-bit unsigned integer Data Coordinate System: Web Mercator Auxiliary Sphere Extent: Global Source: University of Montana Numerical Terradynamic Simluation Group Publication Date: March 10, 2015 ArcGIS Server URL: https://landscape6.arcgis.com/arcgis/ 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 MOD16 Global Evapotranspiration Product, 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 Penman-Monteith 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 MODIS Toolbox.数据集停用通知：本数据集（图层）自2024年4月起进入成熟支持阶段，将于2026年12月正式停用。现有新版本可供使用，Esri建议您尽快更新地图与应用，以适配新版本。 蒸散发（evapotranspiration, ET）即蒸发与蒸腾的综合过程，在水循环中扮演核心角色。降落在陆面的降水可通过溪流、河道形成地表径流，渗入地下，或通过蒸散发返回大气。蒸发过程中的水汽直接返回大气，而蒸腾过程则是植物根系吸收水分后，通过叶片将水汽散失至大气。蒸散发数据可用于计算区域水热平衡与土壤水分状况，为水资源管理提供关键支撑信息。 潜在蒸散发指土壤水分不受限时的理论蒸散发量，仅由气温、太阳辐射与风速等气象参数决定，属于纯气象学特征。实际蒸散发则还受水分可获得性的制约：热带雨林地区的实际蒸散发可接近潜在蒸散发水平，而尽管沙漠地区的潜在蒸散发量更高，实际蒸散发却远低于该值。 数据集概况 制图现象：蒸散发 单位：毫米/年 像元大小：927.6623821756539 米 数据类型：连续型 像素格式：16位无符号整型 数据坐标系：Web墨卡托（Web Mercator）辅助球面 覆盖范围：全球 数据来源：蒙大拿大学数值陆地动态模拟组 发布日期：2015年3月10日 ArcGIS服务器网址：https://landscape6.arcgis.com/arcgis/ 本图层提供像元分辨率为1km的陆面年均蒸散发栅格数据，单位为毫米/年。数据源自蒙大拿大学研究团队基于MODIS影像生成的MOD16全球蒸散发产品。该算法通过估算陆面温度与反照率，并代入彭曼-蒙特斯方程进行计算，但不适用于城市或裸地区域，因此此类区域与所有开阔水域均被标记为无数据（NoData）。针对其余所有像元，算法被用于估算2000年至2014年间每8天周期的蒸散发量，并通过对各周期结果取平均得到年度平均结果。您还可通过MODIS工具箱获取月度蒸散发总量数据。