Relating backscatter from TRMM precipitation radar to surface soil moisture over a semi-arid region
The Tropical Rainfall Measuring Mission Precipitation Radar (TRMMPR) backscatter (σ°) is sensitive to surface soil moisture and vegetation conditions. In arid and semi-arid regions with sparse vegetation cover, TRMMPR σ° primarily depends on the soil water content. In this paper, we show results of the study to relate TRMMPR σ° measurements to soil water content (SM) in Lower Colorado River Basin. A new coupled incidence angle, SM, and Normalized Difference Vegetation Index (NDVI) model of σ° is used to retrieve soil water content. σ° model is calibrated using SM data during 1998 and the calibrated model is used to derive SM during later years. Soil moisture derived from TRMMPR σ° is consistent to observed soil moisture. Figure 1 shows a comparison of derived and observed SM during 1999 with correlation (R) 0.78. Derived SM is also consistent with the measured precipitation data with R=0.76. Spatial distribution of derived soil moisture is compared with the SM estimates from Variable Infiltration Capacity (VIC) hydrological model and have correlation of 0.76 and 0.67 in the wet and the dry seasons, respectively [see Fig. 2]. The accuracy of the σ° soil moisture model reduces under extreme dry and extreme wet surface conditions. Under very dry condition, σ° is dominated by the scattering due to surface geometry and has little contribution from already low soil water content. During very wet period, soil saturation is the main source of errors in the estimates. This research provides an approach to use spaceborne backscatter data for soil moisture retrieval.
Environmental Monitoring | Geographic Information Sciences | Soil Science
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Piechota, T. C.,
Relating backscatter from TRMM precipitation radar to surface soil moisture over a semi-arid region.
2009 AGU Fall Meeting
American Geophysical Union.