Evaluation of SMAP and SMOS Soil Moisture Products Using Distributed Ground Observation Network in Cold and Arid Regions in the Northwest of China

Abstract

Validation of existing satellite soil moisture (SM) products are critical for retrieval algorithms refinement and high-quality SM datasets achievement. Based on distributed ground observations, accuracy performance of two L-band (1.41GHz) passive microwave remotely sensed SM products of SMAP enhanced level 3 (L3) (SMAP-L3) and the newly published SMOS-INRA-CESBIO (SMOS-IC) are evaluated in Heihe River Basin (HRB) over various land surface types in Northwest China. Results reveals that: both two L-band SM products underestimate over grassland and cropland land cover types in HRB, and the underestimation obviously increases with the increasing vegetation effect. Totally, the SMAP L3 product behaves better in capturing the SM variation with the averaged ubRMSE values of 0.03m3/m3 and high R values above 0.6 in ascending orbits for different land cover types in HRB, while the SMOS-IC retrievals are strongly affected by the severe RFI contamination and algorithm uncertainties which need to be handled before application, especially for the descending product.