The response of global terrestrial water storage to drought based on multiple climate scenarios

Drought is a hydrological hazard phenomenon that spreads across the world and will become more intense and frequent with climate change in the future. How to scientifically and effectively monitor and evaluate drought events has become a significant issue. At present, various types of drought monitoring indices have been proposed. However, the criteria for drought that occurs in each month is different and the interaction between drought and the environmental factors of earth is also difficult to understand. To solve this problem, evapotranspiration (ET), leaf area index (LAI), soil moisture (SM), precipitation (P) and surface temperature(ST) data from five different scenarios (Hist-1950, SSP126, SSP245, SSP370 and SSP585) of coupled Model Intercomparison Project Phase6 (CMIP6) were obtained to construct a standardized integrated drought index (SIDI) which was used to monitor drought at global level. Then the cumulative effects of drought on terrestrial water storage in different scenarios were explored. The results showed that the global land surface was a trend of wetting from 1950 to 2014, while the trend of dryness-wetness was different under four future scenarios. Besides, the global drought frequency will first increase and then decrease in the future, and drought frequency in three periods was ranked as follows: Historical period (6.03 months) < Pre-Century (6.15 months) > Post-Century (6.11 months). Moreover, it was found that the cumulative effects of drought on terrestrial water storage diminished gradually from 6.7 months during the historical period (1950–2014) to 5.36 months in the Pre-Century (2015–2057), and further reduced to 4.87 months in the Post-Century (2058–2100), indicating a continuous decline in the stability of global terrestrial water storage in response to drought. This study has a certain reference value for the comprehensive assessment and rational allocation of global terrestrial water storage