Combined Passive and Active Soil Moisture Observations During Clasic

An important issue in advancing higher spatial resolution and better accuracy in soil moisture remote sensing is the integration of active and passive observations. In an effort to address these questions an airborne passive/active L-band system (PALS) was flown as part of CLASIC in Oklahoma over the Little Washita (rangeland and winter wheat) and Fort Cobb watersheds (irrigated agriculture and winter wheat). A total of 11 flight days were flown during the field campaign over each watershed. Extensive ground observations (soil moisture, soil temperature, vegetation) were made concurrent with the PALS observations. These flights were complemented by the acquisition of ALOS PALSAR data. Inter-comparison of radar observations indicated comparative calibration and possibly linear scaling. Extremely wet conditions were encountered during the field experiment. Initial results show the potential of combining passive and active PALS observations. Over the sampling sites PALS radiometer estimated soil moisture was in closer agreement over the Fort Cobb (SEE=0.048 m³/m³) than over the Little Washita watershed (SEE=0.067 m³/m³).