Grid of estimated aridity with a spatial resolution of 10 arc minutes. This dataset represents average yearly precipitation divided by average yearly potential evapotranspiration, an aridity index defined by the United Nations Environmental Programme (UNEP). The classification of the aridity index is: - Classification Aridity Index Global land area - Hyperarid AI < 0.05 - 7.5% of the global land area - Arid 0.05 < AI < 0.20 - 12.1% of the global land area - Semi-arid 0.20 < AI < 0.50 - 17.7% of the global land area - Dry subhumid 0.50 < AI < 0.65 - 9.9% of the global land area