Reply to Suryanarayanan Balasubramanian

Abstract

Analysis of surface energy balance (SEB) at the glacier surface is the most comprehensive way to explain the atmosphere-glacier interactions but that requires extensive data. In this study, we analyse an 11-year (2009–2020) record of the meteorological dataset from an automatic weather station installed at 4863 m a.s.l., on a lateral moraine of the Chhota Shigri Glacier in the western Himalaya. The study was carried out over the winter months (December to April) to understand SEB drivers and snow sublimation. Further, we examine the role of cloud cover on SEB and turbulent heat fluxes. The turbulent heat fluxes were calculated using the bulk-aerodynamic method, including stability corrections. The net short-wave radiation was the primary energy source. However, the turbulent heat fluxes dissipated a significant amount of energy. The cloud cover plays an important role in limiting the incoming short-wave radiation by 70 %. It also restricts the turbulent heat fluxes by around 50 %, consequently less snow sublimation. During the winter period, turbulent latent heat flux contributed the largest (63 %) in the total SEB, followed by net all-wave radiation (29 %) and sensible heat flux (8 %). Sublimation rates were three times higher in clear-sky conditions than overcast, indicating a strong control of cloud cover in turbulent latent heat flux. Dry air, along with the high snow surface temperature and wind speed, favours sublimation. We also observed that strong and cold winds, possibly through mid-latitude western disturbances, impede sublimation by bringing high moisture content in the region and cooling the snow surface. The estimated snow sublimation fraction was 16–42 % of the total winter snowfall at the study site. This indicates snow sublimation is an essential parameter to be considered in the glaciohydrological modelling at the high mountain Himalayan catchments.