Precipitation alone does not properly characterize vegetation water stresses.
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.
In a rapidly changing global environment and climate, these metrics and their derivative indices become a direct and critical measure, and predictive tool, of the trend, direction, and magnitude of climatic change and its impacts upon the terrestrial biosphere, with implications for plant growth, sustainable development, and eventually for human civilization.
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.
Image: Global Aridity Index for the period 1970–2000. Higher values (green/blue colors) represent more humid conditions; low values (yellow/brown/red colors) represent higher aridity. (Credit: Zomer, R.J., Xu, J. & Trabucco, A. Version 3 of the Global Aridity Index and Potential Evapotranspiration Database. Sci Data 9, 409 (2022). https://doi.org/10.1038/s41597-022-01493-1)