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Global Reference Evapotranspiration Layers

The Global Aridity Index (Global-Aridity_ET0) and Global Reference Evapotranspiration (Global-ET0) Version 2 dataset provides high-resolution (30 arc-seconds) global raster climate data for the 1970-2000 period, related to evapotranspiration processes and rainfall deficit for potential vegetative growth, based upon the implementation of a Penman Monteith Evapotranspiration equation for reference crop. The dataset follows the development and is based upon the WorldClim 2.0: at 30 arc seconds or ~ 1km at the equator

Potential Evapo-Transpiration (PET) is a measure of the ability of the atmosphere to remove water through Evapo-Transpiration (ET) processes. Among several equations to estimate PET, a FAO application of the Penman-Monteith equation (Allen et al. 1998), here referred as FAOPM, is currently widely considered as a standard method (Walter et al. 2000). The FAO introduced the definition of PET as the ET of a reference crop (ET0) under optimal conditions, having the characteristics of well-watered grass with an assumed height of 12 centimeters, a fixed surface resistance of 70 seconds per meter and an albedo of 0.23 (Allen et al. 1998). The FAO-PM is a predominately physically based approach, which can be used globally because it does not require estimations of additional site-specific parameters. However, a major drawback of the FAO-PM method is its relatively high need for specific data for a variety of parameters (i.e. windspeed, relative humidity, solar radiation, etc.).

Data citation

Trabucco, Antonio; Zomer, Robert (2019): Global Aridity Index and Potential Evapotranspiration (ET0)
Climate Database v2. figshare. Dataset.


Global-ET0 grid layers are available as monthly averages (12 data layers, i.e. one layer for each month) or as an annual average (1 data layer) for the 1970-2000 period.

Earth Engine Snippet

var et_monthly = ee.ImageCollection("projects/sat-io/open-datasets/global_et0/global_et0_monthly"),
var et_yearly = ee.Image("projects/sat-io/open-datasets/global_et0/global_et0_yearly"),

Sample Code:


The Global-Aridity_ET0 and Global-ET0 datasets are provided for non-commercial use under the CC BY 4.0 Attribution 4.0 International license.

Data Website: You can download the data and description here

Curated by: Samapriya Roy

Keywords: aridity index, evapotranspiration, geospatial modeling

Last updated: 2021-05-09