Submitted to: Journal of Hydrology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/29/2004
Publication Date: 6/1/2005
Citation: Cashion, J., Lakshmi, V., Bosch, D.D., Jackson, T. 2005. Microwave remote sensing of soil moisture: evaluation of the trmm microwave imager (tmi) satellite for the little river watershed tifton, georgia. Journal of Hydrology 307:242-253(2005). Interpretive Summary: The water content in the soil is an important soil characteristic. It is used to evaluate irrigation needs, runoff susceptibility, and plant available water. Knowledge of the amount of water existing in the soil is critical to understanding many of the fundamental environmental processes. Satellite-based sensors offer an effective way to observe soil moisture conditions over large areas. While there are currently several satellite systems that can detect the moisture in the soil, all require extensive testing and calibration. Soil-water measurements collected on the ground within the Little River Watershed (LRWS) near Tifton, Georgia were compared to measurements collected from one of these satellite systems, the Tropical Rainfall Measurement Mission Microwave Imager (TMI). It was found that the TMI was able to observe soil moisture conditions when vegetation levels were low. However, during several months each year high vegetation levels masked the soil moisture signal from the TMI. Estimates were improved by including observations from additional satellite systems which quantify the vegetative cover.
Technical Abstract: Soil moisture plays a critical role in many hydrological processes including infiltration, evaporation, and runoff. Satellite-based passive microwave sensors offer an effective way to observe soil moisture conditions over vast areas. There are currently several satellite systems that can detect soil moisture. Calibration, validation, and characterization of data received from these satellite systems are an ongoing process. Long-term in situ (field) measurements of soil moisture are collected and compared with remotely sensed data. The in situ measurements for this paper were collected at the Little River Watershed (LRWS) Tifton, Georgia and compared to the Tropical Rainfall Measurement Mission Microwave Imager (TMI) 10.65GHz vertical and horizontial (V and H) sensors and vegetation density observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) for the period of 1999 through 2002. The in-situ soil moisture probes exist in conjunction with rain gage stations throughout the sampling region. It was found that the TMI was able to observe soil moisture conditions when vegetation levels were low. However, during several months each year high vegetation levels can mask the soil moisture signal from the TMI. When the observation from the TMI, MODIS, and in situ probes were subjected to a multivariable comparison the correlation value was increased slightly, improving the accuracy of the TMI. After the satellites are adequately calibrated over sampling regions then soil moisture conditions over vast areas can be readily obtained.