Precipitation regime changes in High Mountain Asia driven by cleaner air

Area of Science:

• Climatology
• Atmospheric Science
• Hydrology

Background:

• High Mountain Asia (HMA) faces water resource imbalances due to a South Drying-North Wetting precipitation pattern.
• Climate projections suggest a future wetting trend, but the transition mechanism and timing are unclear.

Purpose of the Study:

• To investigate the drivers of the observed dipolar precipitation pattern in HMA.
• To determine the future trajectory of precipitation changes in HMA under different emission scenarios.

Main Methods:

• Analysis of precipitation data from 1951 to 2020.
• Climate modeling under medium- and high-emission scenarios.
• Investigation of the influence of the Asian westerly jet and Interdecadal Pacific Oscillation.

Main Results:

• The dipolar precipitation pattern is driven by westerly and monsoon precipitation, influenced by weakened Asian westerly jet due to anthropogenic aerosols.
• The Interdecadal Pacific Oscillation contributes to out-of-phase precipitation changes.
• A shift to a monopolar wetting trend is projected for the 2040s under medium/high emissions.

Conclusions:

• Reduced anthropogenic aerosol emissions are key to an intensified jet stream and future wetting trends.
• Policymakers must consider aerosol emission reductions for future water resource management in HMA.