Evaluation of the impact of lakes on passive microwave snow retrieval algorithms using ground-based observation

In this work we chose the Helsinki University of Technology (HUT) snow emission model to character the emission behavior for a snowpack-ice-water system with the ground microwave radiometer observation. This snow and lake ice surveys was conducted in Songhua River, Songyuan city, Jilin Province, on Jan. 21- 22, 2010. Compared to the ground measurements over shallow snow-covered lake ice surface, the simulated brightness temperature at horizontal polarization was better than that at vertical polarizations. The R² of the HUT simulation and measured value was 0.9304 at H-pol, and 0.9194 at V-pol, respectively. Further, we investigated the impact of lake on snow retrieval using passive microwave remote sensing using these ground-based observations. The snow depth in our ground snow survey was almost 5~8cm, ,the brightness temperature difference at the frequencies of 18.7 GHz and 36.5 GHz at V-pol and H-pol was up to -21.4K, -31.9K, respectively. These negative brightness temperature difference (18.7 GHz-36.5 GHz) over lakes caused errors in current SWE retrieval algorithms. Finally, we took sensitivity analysis of ice thickness and snow depth using HUT model on the show that the current brightness temperature difference snow retrieval algorithm was very sensitive to ice thickness, especially in the case of thinner ice. It needed us to make more study in the lake-rich area to improve the snow estimation accuracy.