P1.22 Soil moisture retrieval using an index based approach and passive microwave data from AMSR-E

Thursday, 12 November 2009
Pradipat Sukumal, NOAA/CREST, New York, NY; and M. Temimi and R. Khanbilvardi

This poster addresses the retrieval of soil moisture using an index based approach and passive microwave data from the Advanced Microwave Scanning Radiometer (AMSR-E) for the Earth observing system on-board Aqua satellite. The approach is potentially capable of providing an indication of relative variation of surface wetness condition. Brightness temperature (TB) at low frequencies, such as 6.9 GHz, and 10.7 GHz, has been using to develop an index using linear mixture model. The end members (here after as the TB max and TB min) are extreme value over particular area under driest and wettest conditions, respectively. Two different approaches to derive these end members are evaluated: First, the end members are obtained from all sub-pixels over a particular area (referred to as global) and second, the end members are obtained from pixel-per-pixel over a particular area (referred to as local). Accuracy of the index is assessed using statistics based on a regression coefficient (R). Based on regression analysis, the results indicate that index obtained from the end members derived at local level and using TB at 10.7 GHz is capable of providing reasonable estimate of near surface soil moisture when compared with in-situ soil measurement. The good agreement (R=0.820, RSME=0.05) is achieved over Arizona (SMEX04) region with bare soil surface (mean NDVI<0.3). For the observed lowest correlation coefficient (R=0.416, RSME=0.07) is obtained over dense vegetation area (mean NDVI>0.5) over South Oklahoma. The impact of the vegetation effect on the index needs to be investigating. In addition, the index shows a good relationship with precipitation and volumetric soil moisture variation. However, results have shown that the index responds to precipitation with a lags time of about 1-2 days.

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