Spatial differences in impacts of CO2 effect on China's meteorological droughts: Analysis from surface resistance perspective

Studying impacts of the CO2 effect on potential evapotranspiration (PET) and offline drought indices from surface resistance perspective is significant for understanding and accessing droughts. This study comprehensively investigated impacts of the CO2 effect on PET and Standardized Precipitation-Evapotranspiration Index (SPEI) over China during 1971-2010 based on two simulations with and without CO2 effect, respectively. We found that the CO2 effect led to decreased PET and increased SPEI, and decreased drought, which showed strong spatial variations with the greatest impact over northern China (excluding westernmost part for PET). Such spatial variations had functional relationships not only with CO2 concentration but also climatological conditions, i.e., climatological wind speed (U) and slope of vapour pressure curve (s) for PET, but climatological U, s and pre-cipitation (P) for SPEI. Further analyses implied that climatological U (climatological U and P) determined the spatial variations in the CO2 effect-induced PET (SPEI) changes over China during 1971-2010.