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Title: Combined Passive Active Soil Moisture Observations during CLASIC

Author
item BINDLISH, R - SSAI
item Jackson, Thomas
item SUN, R - BEIJIN NORMAL UNIV
item Cosh, Michael
item YUEH, S - JPL
item DINARDO, S - JPL

Submitted to: Geoscience and Remote Sensing Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2009
Publication Date: 9/1/2009
Citation: Bindlish, R., Jackson, T.J., Sun, R., Cosh, M.H., Yueh, S., Dinardo, S. 2009. Combined passive active soil moisture observations during CLASIC. Geoscience and Remote Sensing Letters. 6:644-648.

Interpretive Summary: A NASA satellite currently under development, the Soil Moisture Active Passive (SMAP) mission, will attempt to combine two techniques (microwave radiometry and radar) to produce a global high accuracy and improved spatial resolution soil moisture product with high temporal frequency. In order to explore the algorithm concepts that might be implemented for SMAP, an experiment was conducted using an aircraft-based prototype of SMAP that was embedded in the Cloud Land Atmospheric Interaction Campaign (CLASIC) conducted over the Southern Great Plains in June 2007. The results demonstrated the complementary information that each sensor can provide and indicated the path that further development should take. These analyses will contribute to the refinement of the SMAP mission design. SMAP will produce a wide range of scientific and societal benefits that include agricultural hydrology, weather and climate forecasts.

Technical Abstract: An important research direction 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 this objective, an airborne instrument, the passive/active L-band system (PALS), was flown as part of CLASIC conducted in Oklahoma in 2007. A total of 11 flight days were flown during the field campaign over each watershed. Extensive ground observations (soil moisture, soil temperature, and vegetation) were made concurrent with the PALS measurements. Extremely wet conditions were encountered during the field experiment. The standard error of estimates (SEE) of the retrieved soil moisture using only the PALS radiometer data for the two watersheds were 0.048 m3/m3 for Fort Cobb and 0.067 m3/m3 for the Little Washita watershed. The radar-only based retrievals had SEEs of 0.092 m3/m3 for Fort Cobb and 0.079 m3/m3 for the Little Washita. Radar retrievals in the Fort Cobb domain were especially poor due to the high vegetation water content of the agricultural fields. The results show the potential of estimating radar based soil moisture over agricultural domains using a vegetation parameterization approach. As expected from previous research, the radiometer based retrievals were better than the radar retrievals. Results also show the potential of combining passive and active PALS observations.