Characterisation of the atmospheric surface layer over a debris cover glacier in the Nepal Himalayas.
Abstract
A significant area of Himalayan glaciers tongues is covered by debris. Turbulent exchanges of sensible and latent heat at the debris surface directly act on its surface energy balance (SEB). At the same time, the large turbulent water vapour exchanges at high altitude modify the debris water content and thus its thermal properties. These must be correctly accounted for in SEB models and a proper characterisation of the atmospheric surface layer (ASL) is therefore needed. We installed an eddy-correlation system (Campbell IRGASON) during a period of 15 days over the Lirung glacier in the Langtang Valley in Nepal in the Nepal Himalaya, during the transition period between the monsoon and the dry season. We present the main characteristics of our set-up and the implication of our ASL characterisation on the parameterisation of the turbulent fluxes. During the day, moderate winds blow up-valley and the ASL is mostly unstable. Latent (sensible) heat fluxes scale between 50 and 150 (50 and 250) Wm-2 during the day, thus drying and cooling the debris and playing a significant role in the SEB. During the night, weak down-glacier winds are observed and fluxes remain weak. Spectral analysis of the turbulent data indicate that flow characteristics do not fulfil theoretical requirements needed to estimate turbulent fluxes using bulk methods and at this site our data show they would work only for the sensible heat flux evaluation.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.C33D1224L
- Keywords:
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- 0720 Glaciers;
- CRYOSPHERE;
- 0736 Snow;
- CRYOSPHERE;
- 0744 Rivers;
- CRYOSPHERE;
- 1621 Cryospheric change;
- GLOBAL CHANGE