Soil Moisture Retrieval Techniques Using the Passive/Active L/S-Band Sensor

Soil moisture plays one of the most important roles in hydrological modeling by determining surface heat fluxes, near-surface moisture gradients and controlling atmospheric effects and climate conditions. Remote sensing of near-surface soil moisture (0-5 cm) has proven beneficial using smaller frequencies in the microwave range (1.4 - 5.6 GHz). This research focuses on evaluating data from the Passive and Active L/S-band instrument (PALS), derived from 5 days of overflights in Chicasha OK during the 1999 Southern Great Plains (SGP) experiment. The effectiveness of the combined radiometer/radar instrument design is analyzed using co-located radiometer observed brightness temperature, radar observed backscatter and surface soil moisture, temperature, and vegetation water content. We attempt to combine; a) observations from PALS, b) statistical regressions c) physically based forward modeling of the sensor and d) retrievals using combinations of b and c. The above has been accomplished in several vegetation regimes; low(<0.25 kg m-2 ), med(0.25-3.0 kg m-2), high(>3.0 kg m-2). In addition, the impact of spatial heterogeneity of soil moisture, vegetation, surface temperature and roughness on the sensor has been examined by applying the forward models to various spatial aggregation schemes.