Global mapping of land surface soil moisture from the water cycle observation mission (WCOM)

Global mapping methods of soil moisture are developed in this study using WCOM (Water Cycle Observation Mission) active/passive multichannel observations. Based on three payloads of WCOM mission with L-S bands passive observations and X/Ku active/passive observations, there are obvious advantages in soil moisture retrieval. Through evaluations of the Advanced Integral Equation Model (AIEM) simulating dataset, it was found that the bare surface emission signals of L-S bands are essentially equal. Accounting for the vegetation effects, the method of soil moisture retrieval with L/S bands can increase soil moisture estimation accuracy, compared with using single L band observations. The RMSE of soil moisture estimated from PALS(Passive Active L- and S-band Sensor) dual frequency radiometer data is 0.048m³/m³ with L band, and RMSE is raised to 0.035m³/m³ with L/S bands. According to the active/passive configuration of WCOM, we developed two soil moisture downscaling methods with active/passive measurements and L-S bands passive measurements, and obtain high resolution soil moisture products. Based on zeroth order approximation model, it was found that there are linear relationship between the L-S band TBs (brightness temperature), and also between the active/passive observations. The RMSE of the spectral active/passive downscaling soil moisture is 0.0459m³/m³. The RMSE of downscaling results of L/S band TB are 2.8 K and 1.7 K for V/H polarization respectively. These results showed that we can get high accurate and high resolution soil moisture products from WCOM and then benefit to various applications.