Cryospheric Applications of Remote Sensing: Snow Water Equivalent

Snow is a critical component of the Earth’s climate system that has high socioeconomic and ecological value. However, the amount of water stored as snow on the land surface, termed snow water equivalent (SWE), is notoriously challenging to remotely sense. This is because snow is often located in forested and/or mountainous environments that obscure remote measurement and induce large spatiotemporal variability in snow depth and density. Multiple approaches have therefore been proposed to remotely sense SWE. This chapter reviews the primary technologies and discusses their strengths and weaknesses. We first describe technologies that retrieve SWE by combining snow depths and density. Next, we discuss technologies that retrieve SWE based on sensitivity of volume scattering within the snowpack. We conclude that, although no single approach has been able to measure SWE at the resolution required for robust water resource management and streamflow forecasting, significant progress has been made using synergistic approaches that fuse multiple sources of data. In the coming decades, several multi-sensor satellite mission concepts are poised to substantially reduce uncertainty in global SWE measurements.