Monitoring of large scale soil moisture from airborne PALS sensor observations during SGP99

Long microwave wavelengths/low frequencies, (1-5 GHz), are especially useful because there is very large contrast between dry and wet soils, little absorption by the atmosphere, and low scattering by vegetation canopy, resulting in analysis over large areas with little or no contamination of the signal. In the present study, data from an airborne, passive/active L and S-band radiometer (PALS) is used to detect soil moisture in the Southern Great Plains. The advantage of using an L (1.4 GHz) and S-band (2.7 GHz) microwave radiometer is that these wavelengths are considered to yield the most accurate soil moisture results over a large range of conditions. The high sensitivity to moisture at the L-band and the increased sensitivity to vegetation at S-band, as well as the increased sensing depth of these long wavelengths have proven these bands can maximize soil moisture sensitivity. Also, the active component of the instrument will add radar backscatter data, which will help interpret surface roughness and vegetation effects on the radiometer observed brightness temperatures. This research will focus on understanding the implications of the PALS instrument´s ability to sense soil moisture at shallow depths over varying conditions using a combination of active and passive data. Working with joint vegetation, soil moisture and surface roughness data, along with information from the PALS instrument, an improvement in the estimation of near-surface soil moisture