Submitted to: Proceedings of the Hydrology Conference
Publication Type: Proceedings
Publication Acceptance Date: 12/7/2001
Publication Date: N/A
Technical Abstract: The Tropical Rainfall Measuring Mission (TRMM Microwave Imager (TMI) provides a least a daily coverage over the southern Continental US. The goal of this project is to develop a soil moisture pathfinder data set using the TMI observations. TMI provides multiple orbits over the southern US at varying times of observation. Methods to adjust for diurnal changes associated with this temporal variability and how to mosaic these orbits are required. The algorithm for deriving soil moisture and temperature from TMI observations is based on a physical model of microwave emission from a layered soil-vegetation-atmosphere medium. Dual polarization observations at 10.65 GHz are used in the retrieval. The land surface is modeled as an absorbing vegetation layer above soil. An iterative, least-squares- minimization method is employed in the retrieval algorithm. Retrieved variables represent area-averages over the 10.65 GHz footprints and also averages over the vertical sampling depth in the soil/vegetation medium. Validation to date has focused on data collected in field campaigns with ground measurements over the US Southern Great Plains (SGP) in Oklahoma and the Little River Watershed, GA. It is important to recognize that these high frequencies respond to a very shallow soil layer (~1-2 cm). Characterizing this layer is difficult and it can change rapidly. The significance of vegetation is very high at these higher frequencies. Based upon further validation and algorithm development, a five year daily soil moisture data set for applicable regions of the southern U.S. will be produced.