Passive microwave soil moisture evaluations by ground based measurements in Korea

Passive microwave sensors have many advantages including the ability to directly measured soil moisture at large spatial scales regardless of weather conditions or time of day. However, microwave-sensed soil moisture's inevitable limitation is that it cannot describe hydrology at the watershed because its retrieved soil moisture scale is too large. Thus, microwave-sensed soil moisture requires validation. Even if there have been great developments for microwave-sensed soil moisture with validation efforts using ground based measurements and land surface models, the validations of the remotely sensed soil moisture in Korea are very limited. This study validated Advanced Microwave Scanning Radiometer E (AMSR-E) soil moisture productions with ground based measurements at eight sites from rural development administration in Korea. The relationship between AMSR-E soil moisture and Normalized Difference Vegetation Index (NDVI) retrieved from Moderate Resolution Imaging Spectroradiometer (MODIS) for estimating soil moisture is also investigated. Overall there was a reasonable agreement between the AMSR-E and ground data, but unreliable replication was found in winter season. More intensive validation efforts should be conducted with other AMSR-E soil moisture products with vegetation information. This type of estimation provides the utility of the AMSR-E soil moisture products and MODIS NDVI as an alternative of the ground based measurements and improves soil moisture retrieval algorithms.