The future state of High Mountain Asia's (HMA) glaciers is of critical importance to water security throughout densely populated regions of Asia. Without understanding regional climatic influences, the prediction of terrestrial water fluxes is not possible. Glacier records in the eastern and central Himalaya (CH) yield some of the world's most rapid retreat rates. However, there are a number of steady state or positive mass-balance glaciers in the Karakoram and western Himalaya (KH) regions. The goal of this research is to investigate multi-annual variations in synoptic wintertime weather as a contributing factor to regional mass-balance trends.

Winter Westerly Disturbances (WWD) are the primary climatic influence within HMA during the boreal winter. This research investigates variations and changes in WWD over the period 1979--2010 and relationships with extreme precipitation in the KH and CH using multiple datasets. It is demonstrated that extreme precipitation events occurring in the KH and CH are often spatiotemporally independent, suggesting differing behavior of WWD affecting each region. The wavelet power spectrum of 200hPa geopotential height anomalies is used to characterize the frequency and magnitude of individual disturbances and to distinguish synoptic scale variability through time. This analysis exhibits an enhancement in the strength and frequency of WWD in the KH and indicates an increase in local extreme precipitation events. In contrast, the CH is observed to experience weakening influence of these disturbances and consequently, a decrease in extreme precipitation. Additionally, peak melt season temperatures are observed to decrease (increase) in the KH (CH) during the study period.

This study also investigates multi-annual variability of WWD and teleconnections with some known modes of climate variability affecting central Asia, including the Arctic Oscillation, the El Nino Southern Oscillation, and the Siberian High. Although there is clear evidence that these modes affect circulation and precipitation in HMA, their competing influences on WWD are complex and non-linear. These results suggest that a thorough understanding of WWD and their spatiotemporal variations are crucial to improve our knowledge of the hydrologic cycle within HMA as well as our ability to project the future status of Asia's water resources.