Soil moisture and rainfall estimation over a semiarid environment with the ESTAR microwave radiometer

The application of an airborne electronically steered thinned array L-band radiometer (ESTAR) for soil moisture mapping was investigated over the semiarid rangeland Walnut Gulch Watershed located In southeastern Arizona. During the experiment, antecedent rainfall and evaporation were very dif ferent and resulted in a wide range of soil moisture conditions. The high spatial variability of rainfall events within this region resulted in moisture conditions with distinct spatial patterns. Analysis showed a correlation between the decrease in bright ness temperature after a rainfall and the amount of rain. The sensor's performance was verified using two approaches. First, the microwave data were used in conjunction with a microwave emission model to predict soil moisture. These predictions were compared to ground observations of soil moisture. A second verification was possible using an extensive data set collected the previous year at the same site with a conventional L-band push broom microwave radiometer (PBMR). Both tests showed that the ESTAR is capable of providing soil moisture with the same level of accuracy as existing systems. ESTAR instruments have the potential to satisfy application data requirements from spaceborne platforms.