First Assessment of the Advanced Microwave Scanning Radiometer 2 (AMSR2) Soil Moisture Contents in Northeast Asia

The Advanced Microwave Scanning Radiometer 2 (AMSR2) onboard the Global Change Observation Mission 1–Water (GCOM-W1) was launched by the Japan Aerospace Exploration Agency (JAXA) in May 2012. The AMSR2 is the follow-on model of the AMSR-Earth Observing System (AMSR-E) onboard the Aqua satellite. An assessment of the reliability of the soil moisture estimations from the newly launched passive sensor, the AMSR2, was carried out in this study, by using in situ soil moisture data from nine locations on the Korean peninsula during the period from July to October, 2012. The temporal patterns of the AMSR2 had a rough association with the in situ soil moisture measurements. However, there was intermittent striking of the AMSR2 data, in comparison to the in situ time series. For a clearer comparison between the variables, normalizing and filtering methods were applied to the AMSR2 soil moisture data with less systematic differences. The error estimation was based on triple collocation, and the AMSR2 data showed a larger error than the in situ and Global Land Data Assimilation System (GLDAS) soil moisture values. The spatial distributions of the monthly AMSR2 soil moisture were analyzed from the perspective of the corresponding reaction of the soil moisture to the spatial distributions of precipitation. The results provided an overview of the AMSR2 soil moisture product that is useful, despite being somewhat limited over the regions in northeast Asia. This study offers an insight into the applicability of the soil moisture products derived from the AMSR2 sensor. However, further studies are required for better understanding of the AMSR2 products for other areas of the validation task.