Calibration of a soil moisture model over grassland using L-band microwave radiometry

Abstract

Land surface models are widely used to simulate water and energy fluxes at the land surface. To perform realistic simulations, an appropriate model parameterization and calibration is required. The present paper investigates the general potential of using L-band microwave radiometer data for the calibration of a simple soil wetness model. A ground based L-band radiometer was used to measure the dual polarized microwave emission from a grass covered area throughout the vegetation period in 2004. It was found that L-band microwave data provided a robust proxy for surface soil moisture conditions for the used data set which is consistent with previous findings. The microwave data is used for the calibration of a simple soil moisture model. Using the L-band data resulted in improved simulation skills of surface soil water dynamics as well as a better representation of deeper soil water storage. The correlation r between the soil moisture model estimates and the actual soil moisture was improved from to for the surface and (root zone) soil water content, respectively. The results of the study reveal the general potential of using L-band microwave radiometry for an improved parameterization of land surface models which might be an interesting application for proposed and recent L-band microwave satellite missions such as the NASA Soil Moisture Active/Passive (SMAP) and the European Soil Moisture and Ocean Salinity Mission (SMOS).