Annual temperature and radiobrightness signatures for bare soils

We have developed physically based diurnal and annual models for freezing/thawing moist soils subject to annual insolation radiant heating and cooling and sensible and latent heat exchanges with the atmosphere. Both models have the same weather forcing numerical scheme and soil constitutive properties. We find that surface temperature differences over a diurnal cycle between the annual and diurnal models are as much as -5 K in March -7 K in June -4 K in September and 5 K in December for 38% (by volume traction) moist soil. This difference occurs because the annual model includes the history of energy fluxes at the surface of the soil. The annual model is linked to microwave emission models for predictions of temporal radiobrightness signatures. The model predicts a relatively weak decrease in diurnal differences in soil temperature with increased moisture content but a significant decrease in diurnal differences in radiobrightness. It also exhibits notable perturbations in radiobrightness when soils freeze and thaw. The moisture dependent day-to-night radiobrightness difference is enhanced by as much as -42 K at 19.35 GHz horizontal polarization for frozen soil if daytime thawing occurs.