Dataset Discrepancies Dominate Present and Future Precipitation-Glacier Relationships Across High Mountain Asia

High Mountain Asia (HMA) provides crucial water resources to more than 1.5 billion people and accurate quantification of high elevation precipitation in this region is essential for understanding the hydrological cycle, patterns of ongoing climatic change, and water resource management. This is particularly the case in high elevation, glacierised catchments where the interplay of cryospheric and atmospheric processes limits our understanding of current and future water resource availability. The role of precipitation and snow accumulation is critical for the health of glaciers which represent both an important freshwater storage and hydrological buffer to drought conditions. In both present-day and future modelling scenarios, precipitation at both macro and local scales generate some of the greatest uncertainties in glacier response to climate, especially across the distinct hydro-climatic regions of HMA.

 

We leverage precipitation estimates across several regional gridded products with a high spatial (>= 10 km) and temporal (hourly) resolution to explore their discrepancies over glacierised regions of HMA for the period of 2001-2019. Our analyses demonstrate a substantial disagreement between precipitation datasets in terms of i) their annual and seasonal magnitudes, ii) the fraction of precipitation occurring during the summer/monsoon period, iii) the differences of precipitation amounts between decades, iv) the correlation of precipitation amounts to annual mass balances, v) diurnal precipitation frequency and, vi) dependence on elevation and topographic complexity. 

 

Using the Open Global Glacier Model (OGGM), we demonstrate that the selection of precipitation input data can lead to widely differing interpretations of the role of precipitation as a driver of mass balance variability under a future climate and create substantially different estimations of runoff that exceed the differences due to the choice of climate model.

At catchment scales, the spatial extent and seasonality of precipitation, as well as the representation of specific storm events are all critical for the accurate estimation of glacier energy and mass balance. Fully-physical modelling of well-monitored, glacierised catchments across HMA reveals that the timing of precipitation events can be equally important to the long-term mass balance of glaciers as the monthly amounts of precipitation from different datasets.  

Finally, we discuss the regions of greatest disagreement and highlight further investigations linking precipitation and glacier health under present and future climate.