Estimating the Effective Soil Temperature at L-Band as a Function of Soil Properties.

To retrieve soil moisture from L-band microwave radiometry, it is necessary to account for the effects of temperature within both vegetation and soil media. To compute the effective soil temperature T_G, several simple formulations accounting for soil temperatures at the surface and at depth and surface soil moisture have been developed. However, the effects of the soil physical properties in terms of texture, density, or structure, which all may be important variables in the modeling of T_G, have never been investigated. In this paper, several simple formulations of T_G at L-band, accounting for or ignoring the effects of soil texture and density, were developed and compared based on a very large simulated data set. The best configurations and parameterizations of these simple formulations were computed and could be directly used for operational applications in future soil moisture retrieval studies. For instance, we showed that the use of the surface temperature in the estimation of T_G can be significantly improved by using additional information on the soil temperature at depth (the average error in the estimation of T_G decreased from ∼4 to ∼1.8 K). On the contrary, almost no improvement was obtained if air temperature was used instead of surface temperature. Also, it is shown that the use of additional information on the soil properties, mainly the soil clay content and density, led to improved results by about 0.2 K in the estimation of T_G. The improvement was found to be larger for sandy and dry soils: simplified formulations accounting for soil properties are able to represent the fact that T_G is closer to the soil temperature at depth for these soil conditions. [ABSTRACT FROM AUTHOR]