The Role of Observed Air Temperature and Local Winds in Glacier Mass BalanceModeling: Chhota Shigri Glacier, Western Himalaya

Near-surface air temperature (Ta) is crucial for glacio-hydrological modeling, yet measuring
and modeling it in glacierized regions is challenging due to spatial variability. On-glacier Ta
data is scarce in the Himalaya, and in these regions, katabatic winds significantly influence
Ta, and linear extrapolation of Ta from off-glacier does not perform well. This study focuses
on the Chhota Shigri Glacier in the Western Himalaya, examining how local wind systems,
particularly katabatic and valley winds, influence Ta and glacier mass balance (MBs). Using
data from nine on-glacier and three off-glacier weather stations during the summer of 2022,
the study highlights interactions between winds and Ta variability across the glacier surface.
Katabatic winds, which accounted for 89% of the observed data, cooled near-surface Ta by
up to 2°C compared to temperatures extrapolated using linear lapse rates (LRs). This cooling
effect, most pronounced during midday, significantly influenced the glacier's thermal regime
and highlighted the limitations of linear LRs in capturing Ta variability. The piecewise linear
regression approach (SM10 model), incorporating katabatic wind effects, was applied to
extrapolate on-glacier Ta. Modeled Ta (SM10) and extrapolated Ta (using LRs) were used in
a temperature index model to simulate point mass balance (MBs) and compare with in-situ
MB observations (using stake data). When validated against in-situ measurements, LR-based
models overestimated point MBs by up to 92%, while the SM10 model reduced the errors to
just 8%.
These results highlight the crucial role of local winds in regulating glacier surface
temperatures and emphasize the need to account for the katabatic wind effect in MBs
modeling. This study enhances the integration of observed Ta into glacio-hydrological
models by analyzing the “glacier cooling effect,” advancing the understanding of glacier-
atmosphere complex interactions in the Himalayan terrain and improving the accuracy of
melt and mass balance studies.