Abstract
In the Central Himalayas, glaciers and snowmelt play an important hydrological role, as they ensure the availability of surface water outside the monsoon period. To compensate for the lack of field measurements in glaciology and hydrology, high temporal and spatial resolution optical remotely sensed data are necessary. The French–Israeli VENµS Earth observation mission has been able to complement field measurements since 2017. The aim of this paper is to evaluate the performance of different reflectance products over the Everest region for constraining the energy balance of glaciers and for cloud and snow cover mapping applied to hydrology. Firstly, the results indicate that a complete radiometric correction of slope effects such as the Gamma one (direct and diffuse illumination) provides better temporal and statistical metrics (R2 = 0.73 and RMSE = 0.11) versus ground albedo datasets than a single cosine correction, even processed under a fine-resolution digital elevation model (DEM). Secondly, a mixed spectral-textural approach on the VENµS images strongly improves the cloud mapping by 15% compared with a spectral mask thresholding process. These findings will improve the accuracy of snow cover mapping over the watershed areas downstream of the Everest region.
Highlights
Hosting the highest mountains in the world and the largest glacierized area outside of the polar regions, the Himalayas are a unique hydro-climatic system
The aim of this study was to evaluate and quantify the performance of different products retrieved by the CNES processing of the VENμS database over the Everest region in Nepal for glaciological and hydro-climatic applications
In such a high-mountain context, the focus was set on the interest in adding a fine digital elevation model (DEM) to the processing chain to enhance the pre-existing quality of the high temporal and spatial resolution from remote data provided by the VENμS sensor
Summary
Hosting the highest mountains in the world and the largest glacierized area outside of the polar regions, the Himalayas are a unique hydro-climatic system. These high mountains are often called “water towers” for the buffering role they play in the Asian water cycle [1,2,3] with snow and ice melt maintaining streamflow during periods of meteorological drought [3,4,5]. This region is a challenge for high-elevation glacio-hydrologic research.
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