Impact of Soil Permittivity and Temperature Profile on L-Band Microwave Emission of Frozen Soil

An unexplored aspect of L-band microwave emission is the impact of soil moisture and soil temperature (SMST) profile dynamics on diurnal brightness temperature ( T_{\mathrm {B}} ) signatures of frozen soil. This study investigates this effect by comparing the T_{\mathrm {B}} simulations of layered ( T_{\mathrm {B,l}} ) and uniform ( T_{\mathrm {B,u}} ) soils using a newly developed integrated land emission model. The multilayer Wilheit model and the single-layer Fresnel model are adopted to compute the smooth soil reflectivity for the layered and uniform soils, respectively. A four-phase dielectric mixing model is used to calculate the soil permittivity ( \varepsilon _{s} ). A data set of concurrent ELBARA-III T_{\mathrm {B}} and SMST profile measurements performed in a seasonally frozen Tibetan meadow ecosystem is used for the analysis. The simulated T_{\mathrm {B,l}} considering SMST profile information captures well the ELBARA-III measurements with low biases (≤6 K) and high correlations ( R^{2}\ge0.88 ). T_{\mathrm {B,u}} produced based on the Fresnel model using the soil moisture of 2.5 cm is more consistent with the T_{\mathrm {B,l}} . The sensitivity test of averaging SMST profile below 2.5 cm leads to maximum differences of 2 K in T_{\mathrm {B,l}} simulations, indicating that the T_{\mathrm {B}} variations are primary dominated by the SMST dynamics at the surface layer. A sensitivity test of the Wilheit model to different \varepsilon _{s} parameterizations shows that the dielectric model of Zhang et al. is comparable to the fou