HUT snow emission model and its applicability to snow water equivalent retrieval

The derivation, testing, and employment to parameter retrieval of the Helsinki University of Technology (HUT) snow microwave emission model is presented. The radiative transfer-based semi-empirical model describes the emission behavior of a homogeneous snowpack as a function of water equivalent (SWE), effective grain size, and density of snow. Additionally, the modeling approach takes into account the influence of soil surface, forest canopy, and atmosphere to spaceborne observed brightness temperature by using empirical and semi-empirical formulas. The comparison of model predictions with independent experimental data shows good correlations, especially in terms of spectral characteristics. This enables the development of a new inversion technique for the SWE retrieval from spaceborne data based on the developed model. The test results using special sensor microwave/imager (SSM/I) data from boreal forest zone showed SWE retrieval accuracies considerably higher than those obtained with conventional algorithms. A discussion and analysis on the feasibility of the new SWE retrieval technique for operational applications is also included.