The global map of aridity
Precipitation alone does not properly characterize vegetation water stresses. Indeed, water needs of plants or crops to maintain their physiological processes – the evapotranspiration – depends on many meteorological and climatic variables, including solar radiation, air temperature, relative humidity and wind speed, as well as specific crop characteristics and cultivation practices.
Aridity indices are therefore implemented to measure the adequacy of the precipitation to satisfy vegetation water requirements, namely as ratio of annual precipitation to evapotranspiration of reference crop, or Potential EvapoTranspiration.
An international team of scientists has released a set of updated and improved estimations of Potential Evapotranspiration and an Aridity Index for the entire world. The peer-reviewed article describing the database has recently been published in the Nature journal – Scientific Data. The database presents the values of the indices for the entire globe at a very high spatial resolution of approximately 1 km2 for the period 1970-2000, and as baseline for future projections.