Review article: Global monitoring of snow water equivalent using high-frequency radar remote sensing

• Published in: The Cryosphere
• Main Authors: L. Tsang, M. Durand, C. Derksen, A. P. Barros, D.-H. Kang, H. Lievens, H.-P. Marshall, J. Zhu, J. Johnson, J. King, J. Lemmetyinen, M. Sandells, N. Rutter, P. Siqueira, A. Nolin, B. Osmanoglu, C. Vuyovich, E. Kim, D. Taylor, I. Merkouriadi, L. Brucker, M. Navari, M. Dumont, R. Kelly, R. S. Kim, T.-H. Liao, F. Borah, X. Xu
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2022
• Subjects: Environmental sciences; GE1-350; Geology; QE1-996.5; Arctic; Sea ice; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-16-3531-2022; https://doaj.org/article/3fc8bc82560543a6b98ee097709577ea

Seasonal snow cover is the largest single component of the cryosphere in areal extent, covering an average of 46 × 10 6 km 2 of Earth's surface (31 % of the land area) each year, and is thus an important expression and driver of the Earth's climate. In recent years, Northern Hemisphere spring snow cover has been declining at about the same rate ( ∼ −13 % per decade) as Arctic summer sea ice. More than one-sixth of the world's population relies on seasonal snowpack and glaciers for a water supply that is likely to decrease this century. Snow is also a critical component of Earth's cold regions' ecosystems, in which wildlife, vegetation, and snow are strongly interconnected. Snow water equivalent (SWE) describes the quantity of water stored as snow on the land surface and is of fundamental importance to water, energy, and geochemical cycles. Quality global SWE estimates are lacking. Given the vast seasonal extent combined with the spatially variable nature of snow distribution at regional and local scales, surface observations are not able to provide sufficient SWE information. Satellite observations presently cannot provide SWE information at the spatial and temporal resolutions required to address science and high-socio-economic-value applications such as water resource management and streamflow forecasting. In this paper, we review the potential contribution of X- and Ku-band synthetic aperture radar (SAR) for global monitoring of SWE. SAR can image the surface during both day and night regardless of cloud cover, allowing high-frequency revisit at high spatial resolution as demonstrated by missions such as Sentinel-1. The physical basis for estimating SWE from X- and Ku-band radar measurements at local scales is volume scattering by millimeter-scale snow grains. Inference of global snow properties from SAR requires an interdisciplinary approach based on field observations of snow microstructure, physical snow modeling, electromagnetic theory, and retrieval strategies over a range of scales. New field ...