Global Aridity Index and Potential Evapotranspiration Database: CIMP_6 Future Projections

Abstract

We present the recent release of the “Global Aridity Index and Potential Evapotranspiration Database: CIMP_6 Future Projections – v.1 (Future_Global_AI_PET)”, which provides very high-resolution (30 arc-seconds or about 1km at equator) global raster dataset of average monthly and annual potential evapotransipation (PET) and annual aridity index (AI) for two historical (1960-1990; 1970-2000) and two future (2021-2040; 2041-2060) time periods for each of 25 CIMP6 Earth System Models across four emission scenarios (SSP: 126, 245, 370, 585). Potential evapotranspiration (PET) characterizes the atmosphere's capacity to remove water through evapotranspiration (ET). Evaporation and transpiration processes collectively transfer water from the Earth's surface to the atmosphere with rates determined by solar radiation, air temperature, relative humidity (specifically, vapor pressure deficit), wind speed, as well as the distinctive traits of vegetation, or crops and the practices employed in their cultivation. Estimates of reference evapotranspiraton (ET0) have been widely used across diverse scientific fields and practical domains, with PET measurements and related indices playing a crucial role in agricultural and natural resource management with demonstrated utility on scales from individual farms to regional and global. The aridity index (AI), which describes the ratio of precipitation to PET provides an integrated measure to gauge moisture availability for plant growth, generally of specific reference crops or specific vegetation types, enabling both spatial and temporal comparisons. In an era of rapid environmental and climatic transformations, these metrics, along with their derived indices, assume a pivotal role as direct and critical measures, as well as predictive tools, for gauging the trajectory, direction, and extent of climatic variations and their ramifications for terrestrial, and particularly agricultural, ecosystems. This latest addition to the Global_AI_PET database also includes three averaged multi-model ensembles produced for each of the four emission scenarios: All Models:  includes all of the 25 ESM available; High Risk: includes 5 ESM which were identified as projecting the highest increases in temperature and significantly higher than the majority of estimates; Majority Consensus:  includes 20 ESM, that is, all of the available ESM minus the five ESM in the “High Risk” category.  Preliminary results based on CIMP6 ESM projections are provided showing significant change in global and regional trends for PET and aridity in the near- and medium-term, with implications for agriculture, biodiversity, watershed management, and water resources. The Future_Global_AI_PET Database is the latest and most recent addition to the Global PET_AI Database, which has provided PET and AI datasets using both the Hargreaves and Penman-Monteith equations, and has been available online since 2009, downloaded over 50,000 times, and with more than 2000 scholarly citations:  https://figshare.com/articles/dataset/Global_Aridity_Index_and_Potential_Evapotranspiration_ET0_Climate_Database_v2/7504448/6)