Snow water equivalent monitoring from dual-frequency scatterometer on WCOM

Abstract

Water Cycle Observation Mission (WCOM) is a mission dedicated to synergetic observations of global water cycle parameters, with emphasis on soil moisture, ocean surface salinity, snow water equivalent and frozen/thaw. WCOM implements its observation requirements by measurement of microwave emission/scattering of both the frequencies sensitive to the key parameters and also the auxiliary frequencies providing necessary atmospheric and surface roughness corrections. In order to satisfy this measurement requirements, WCOM is equipped with payloads with combination of active and passive microwave sounding capabilities of frequency from L-band to W-band. Dual Frequency Polarized Scatterometer (DFPSCAT) is one of the three payloads onboard the satellite of Water Cycle Observation Mission (WCOM). DFPSCAT is an X/Ku band rotating pencil beam scatterometer with 2–5 km resolution and 1000km swath for mapping of snow water equivalent (SWE) and freeze-thaw process. DFPSCAT achieves fine resolution by linear frequency modulation pulse compression along the elevation direction, and by unfocused synthetic aperture processing (a technique where the Doppler effect is exploited to synthesize a longer aperture to achieve an improved resolution), as well as super-resolution reconstruction by oversampling in the direction of the azimuth. Based on the payloads of WCOM mission, especially with X/Ku scatterometer and L/Ku/Ka radiometer active/passive observations, there are obvious advantages in snow water equivalent retrieval. The atmospheric correction of active and passive data should be performed before the retrieval. The estimation of SWE mainly rely on the high resolution X and Ku band scatterometer, and combined active/passive retrieval can provide more reliable SWE product. The retrieval method of SWE from X/Ku scatterometer is described, and combined active/passive retrieval is also briefly described.