2024 Volume 37 Issue 3 Pages 249-255
The Advanced Microwave Scanning Radiometer 2 (AMSR2) L2 soil moisture product in V3.0 from the Japan Aerospace Exploration Agency (JAXA) was evaluated using in situ hydrological data obtained during 2012-2021 on the Mongolian Plateau. Regarding the relation between the AMSR2 soil moisture from descending orbits and in situ measured soil moisture at 3 cm depth, the root mean square error (RMSE: m3/m3) and bias (m3/m3) values varied respectively from 0.025 to 0.063 and from 0.011 to -0.051. Comparison of the Soil Moisture and Ocean Salinity (SMOS) soil moisture product in V700 with AMSR2 L2 revealed that the AMSR2 observed surface soil moisture with nearly equal accuracy and stability to those of SMOS. However, the bias values of the AMSR2 soil moisture measurements were inferior to those of SMOS, which measured soil moisture at increased depths. The RMSE and bias values of AMSR2 were more dependent on rainfall conditions than those of SMOS. These results suggest that underestimation of AMSR2 soil moisture measurements possibly occurred because of the difference between the depth of AMSR2 observations and the in situ area averaged soil moisture measurements. Overall, the AMSR2 L2 soil moisture product, with its high measurement accuracy, has been useful for studying ground surface changes and for monitoring daily surface soil moisture over large grassland areas since 2012.
