Cross-validation of soil moisture data from AMSR-E using field observations and NASA's Land Data Assimilation System simulations

Soil moisture is a critical hydrosphere state variable that often limits the exchanges of water and energy between the atmosphere and land surface, controls the partitioning of rainfall between evaporation and runoff, and impacts vegetation photosynthetic rate and soil microbiologic respiratory activities. Thus, accurate measurements of this variable are required for the global water and energy cycles as well as the carbon cycle. A global soil moisture data product is continuously generated from the observations of the Advanced Microwave Scanning Radiometer (AMSR-E) onboard NASA's Aqua satellite. The accuracy of this data product has not yet been validated and the assessment of the product quality is required for its various applications. A series of field experiments (SMEX02, Iowa; SMEX03, Georgia; SMEX04, Arizona; SMEX05, Iowa) have been conducted to address problems related to the hydrologic processes and validate AMSR-E soil moisture measurements. During these experiments, soil moisture values were obtained from both the Theta probes and gravimetric sampling for the 0-6cm surface layer for the dozens of sites that were selected to represent the footprints of the AMSR-E. A careful comparison between these observations and the corresponding AMSR-E retrievals has been carried out. To further understand the quality of these soil moisture retrievals, the NOAH land surface model in NASA's Land Data Assimilation System (LDAS) was run with the best available forcing data sets to produce the surface soil moisture data corresponding to the AMSR-E retrievals and the field observations. Results from comparing the AMSR-E retrievals, the LDAS simulations and the field observations will be presented to demonstrate the characteristics of the current AMSR-E soil moisture data product.