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Processing of VENµS Images of High Mountains: A Case Study for Cryospheric and Hydro-Climatic Applications in the Everest Region (Nepal)

Research output: Contribution to journalArticlepeer-review

Zoé Bessin, Jean Pierre Dedieu, Yves Arnaud, Patrick Wagnon, Fanny Brun, Michel Esteves, Baker Perry, Tom Matthews

Original languageEnglish
Article number1098
JournalREMOTE SENSING
Volume14
Issue number5
Early online date23 Feb 2022
DOIs
Accepted/In press19 Feb 2022
E-pub ahead of print23 Feb 2022
Published1 Mar 2022

Bibliographical note

Funding Information: This work has been funded and supported by the French Service of Observation GLACI-OCLIM, now called CRYOBS-CLIM, part of IR OZCAR, and by the French National Research Agency (ANR) through the PRESHINE project, Grant Number ANR-13-SENV-0005. Acknowledgments: This research was part of the selected “Pointing” project from the CNES-ISA VENµS Program, thanks to CNES for the VENµS images collection (KHUMBU site). The authors are grateful to G. Dedieu and O. Hagolle from CESBIO-CNES for their support and advice, S. Pelou from CNES for technical imaging help. Thanks to L. Davaze (IGE) for his help concerning the cosine correction processing and to S. Gascoin (CESBIO-CNES) for the HMA DEM providing. The in situ measurements at Changri Nup and Pyramid sites have been supported by the JEAI HIMALICE Program (PIs: D. Shrestha, and Y. Arnaud), within the framework of the Ev-K2-CNR Project in col-laboration with the Nepal Academy of Science and Technology and Tribhuvan University. We are deeply grateful to the National Geographic Society concerning fieldwork measurements at the South Col site: the albedo data collection was conducted in partnership with the National Geographic Society, Rolex, and Tribhuvan University, with approval from all relevant agencies of the Government of Nepal. Special thanks to Aurora Elmore from the National Geographic Society for her review and advice. Funding Information: Funding: This work has been funded and supported by the French Service of Observation GLACI-OCLIM, now called CRYOBS-CLIM, part of IR OZCAR, and by the French National Research Agency (ANR) through the PRESHINE project, Grant Number ANR-13-SENV-0005. Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

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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.

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