Attribution of Dry and Wet Climatic Changes over Central Asia

Central Asia (CA; 35 degrees-55 degrees N, 55 degrees-90 degrees E) has been experiencing a significant warming trend during the past five decades, which has been accompanied by intensified local hydrological changes. Accurate identification of variations in hydroclimatic conditions and understanding the driving mechanisms are of great importance for water resource management. Here, we attempted to quantify dry/wet variations by using precipitation minus evapotranspiration (P2E) and attributed the variations based on the atmosphere and surface water balances. Our results indicated that the dry season became drier while the wet season became wetter in CA for 1982-2019. The land surface water budget revealed precipitation (96.84%) and vapor pressure deficit (2.26%) as the primary contributing factors for the wet season. For the dry season, precipitation (95.43%), net radiation (3.51%), and vapor pressure deficit (-2.64%) were dominant factors. From the perspective of the atmospheric water budget, net inflow moisture flux was enhanced by a rate of 72.85 kg m(-1) s(-1) in the wet season, which was mainly transported from midwestern Eurasia. The increase in precipitation induced by the external cycle was 11.93 mm (6 months)(-1). In contrast, the drying trend during the dry season was measured by a decrease in the net inflow moisture flux (74.41 kg m(-1) s(-1)) and reduced external moisture from midwestern Eurasia. An increase in precipitation during the dry season can be attributed to an enhancement in local evapotranspiration, accompanied by a 4.69% increase in the recycling ratio. The compounding enhancements between wet and dry seasons ultimately contribute to an increasing frequency of both droughts and floods.

Automated summary

Central Asia has been experiencing significant warming and intensified hydrological changes. The wet season has become wetter and the dry season has become drier. Precipitation and vapor pressure deficit are the primary factors for the wet season, while precipitation, net radiation, and vapor pressure deficit are dominant factors for the dry season. Enhanced moisture flux from midwestern Eurasia contributes to increased wet season precipitation, while decreased moisture flux and enhanced local evapotranspiration explain the drying trend in the dry season.