The simulated sea ice thermal microwave emission at window and sounding frequencies

Abstract

Although the sea ice microwave emissivity is well defined in terms of brightness temperature and the effective temperature it is difficult to derive in practice and its link to physical processes in the snow and sea ice cover is not understood in detail. Future applications of assessing the sea ice microwave emission potentially include atmospheric sounding over sea ice for channels peaking near the surface. Here the microwave emission processes from sea ice are simulated using the combination of a one-dimensional thermodynamic snow and sea ice model and a microwave emission model. The emission model is a sea ice version of the Microwave Emission Model for Layered Snow-packs (MEMLS). It is demonstrated that the simulated seasonal variability of the emissivity, the spectral gradient and the polarization are comparable to satellite measurements. The spectral gradient ratio defined as the difference over the sum of the 18 and 36 GHz at vertical polarization is related to the emissivity at the atmospheric temperature sounding channels at around 50 GHz. Further the brightness temperature at neighbouring channels is highly correlated. However, the effective temperature at lower frequencies (18, 23, 36 and 50 GHz) is poorly correlated with the surface or air temperature.