Rethinking Monsoon- and Westerly Disturbance-Dominated Precipitation Dynamics and Impacts on the Cryosphere in High Mountain Asia
Abstract
Comparisons and discussions of cryospheric, atmospheric, hydrologic, and hazards systems across High Mountain Asia (HMA) are often done within the context of the regional climate system. In particular, HMA is often geographically divided based on whether the precipitation in the region is dominated by the summer monsoon or winter westerly disturbances. This is a useful approach as the seasonality, frequency, and intensity of precipitation plays a significant role in the sensitivity of HMA systems to changes in climate. Unfortunately, the complex terrain and sparse distribution of weather stations limit the understanding of mountain precipitation. While gridded precipitation datasets are available, they tend to be at resolutions insufficient for resolving the terrain and thus do not adequately capture the spatial and temporal distribution of precipitation in higher elevation regions. Therefore, the definitions of summer (monsoon)-dominated and winter (westerly disturbance)-dominated precipitation regions are likely highly uncertain.
Here we examine precipitation dynamics in HMA using dynamically downscaled climate output at 4 km spatial resolution. Our analyses show a complex pattern in precipitation seasonality that depends significantly on elevation and water vapor transport direction. In general, westerly disturbances become progressively important as elevation increases, including in regions traditionally identified as monsoonal. In addition, the relative contribution of large storms to total annual precipitation decreases with increasing elevation. These results demonstrate the spatial complexities in the timing, intensity, and frequency of precipitation in HMA when viewed through a topographic lens. As an example of the importance of precipitation statistics in HMA, we model changes in glacier mass balance under future climate warming scenarios across HMA. Our results show that projections of glacier change depend primarily on changes in temperature, but the magnitude and spatial heterogeneity in glacier response to temperature will be impacted by the precipitation setting as well. Thus, improving understanding of orographic precipitation over HMA will be a critical step towards improving discussions, analyses, and modeling of HMA systems.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C43A..01R
- Keywords:
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- 0720 Glaciers;
- CRYOSPHERE;
- 0740 Snowmelt;
- CRYOSPHERE;
- 0758 Remote sensing;
- CRYOSPHERE;
- 0776 Glaciology;
- CRYOSPHERE