New Drought Projections Over East Asia Using Evapotranspiration Deficits From the CMIP6 Warming Scenarios

In this work, we projected future drought risks over East Asia from the perspective of evapotranspiration (ET) deficit using the new climate projections of the Coupled Model Intercomparison Project Phase 6 (CMIP6). For the regional drought projections, we employed a state-of-the-art complementary relationship (CR) method to estimate ET and atmospheric evaporative demand (E_p) that quantify the combined impact of water deficiency and vapor pressure deficit stress. The performance of the CR method was validated using the reanalysis climate data and independent water-balance ET estimates. The same CR method was again applied to hindcasts and projections of seven global climate models (GCM) in the CMIP6 archive. Results showed that the CR ET estimates and the GCM-driven ET products were both able to approximately close the basin-scale water balance and tightly correlated with each other. The application with the CMIP6 GCM hindcasts provided the same indication that the CR ET and the GCM-driven ET are consistent. The drought assessments using the ET deficit (ET − E_p) from the CMIP6 projections implicates that future drought risks over East Asia would be much higher than indicated by precipitation or soil moisture projections. Rising trends of E_p are expected to outpace those of ET even under the medium-level greenhouse gas emission scenario. Our new drought projections suggest that E_p amplified by soil water deficiency could raise agricultural and wildfire risks substantially by the end of the 21st century.