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

Abstract

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 (Ep) 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 − Ep) 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 Ep are expected to outpace those of ET even under the medium‐level greenhouse gas emission scenario. Our new drought projections suggest that Ep amplified by soil water deficiency could raise agricultural and wildfire risks substantially by the end of the 21st century.

Long-Term Projection of Water Cycle Changes over China Using RegCM

“…In terms of seasonal variations, summer and spring are likely to see larger increases in evapotranspiration; this feature is consistent with Ma et al's observation [59]. The developed projections in evapotranspiration can be used to evaluate climate change impacts on drought conditions through the calculation of evapotranspiration deficit; this index, compared with those that are based on precipitation and soil moisture, could more effectively reflect moisture deficiency in ecosystems [60].…”

Contributions of Local Land‒Atmosphere Coupling and Mesoscale Atmospheric Circulation to the 2013 Extreme Flash Drought and Heatwave Compound Event Over Southwest China

“…The increasing trends of Ep are anticipated to exceed those of ET, even in the medium‐level greenhouse gas emission scenario. The amplification of Ep due to soil water deficiency could significantly increase agricultural and wildfire risks by the end of the 21st century (Kim et al., 2021). The greenhouse effect of the future is projected to impact the traits of the worldwide monsoon system, specifically the heightened volatility experienced by the Asian summer monsoon system.…”

Revisiting a Two‐Parameter Budyko Equation With the Complementary Evaporation Principle for Proper Consideration of Surface Energy Balance

“…E p and E pmax are typically estimated using the open‐water Penman (1948) equation with relevant forcing inputs (e.g., Kim, Lee, et al., 2019; Kim et al., 2021; Kyatengerwa et al., 2020; Ma et al., 2019; Ma & Szilagyi, 2019): where, Δ avg (kPa °C −1 ) is the slope of the saturation vapor curve at mean air temperature T avg (°C), γ (kPa °C −1 ) is the psychrometric constant, R n (MJ m −2 d −1 ) is the surface net radiation, λ v (MJ kg −1 ) is the latent heat of vapourization by λ v = 2.501–0.00236×T avg (for T avg > 0) or λ v = 2.835 (otherwise), f u (mm d −1 kPa −1 ) is the empirical wind function of f u = 2.6(1 + 0.54u 2 ), where u 2 is the 2‐m wind speed (m/s), e s is the saturation vapor pressure, and T dew (°C) is the dew point temperature. Δ dry (kPa °C −1 ) is the slope of the saturation vapor curve at the dry air temperature T dry .…”

“…E p and E pmax are typically estimated using the open-water Penman (1948) equation with relevant forcing inputs (e.g., Kim, Lee, et al, 2019;Kim et al, 2021;Kyatengerwa et al, 2020;:…”