Research On The Variation Of Namco Lake Ice By Passive Microwave Remote Sensing

Lake ice can respond quickly to the temperature changes under the background of global climate change, it can be able to act as an effective indicator to monitor climate change for the actual effect. At present, the research on lake-ice both at home and abroad are rather lacking, the size of the lake, the requirements for temporal resolution are important factors that limited the study for lake ice.The data with High temporal resolution, not affected by the cloud is of the utmost importance for Lake ice research. In this context, the SMMR and SSM/I passive microwave brightness-temperature data were applied to the study.There were significant differences between the brightness-temperature of lake ice and water. According to this difference we can extract the four parameters(began to freeze, completely frozen, began to thaw and the complete ablation) of Nam Co Lake form1978-2013by searching for the mutation position from brightness temperature values.We validated the result by AMSE-E data, MODIS data, as well as other related studies, and focused on the analysis of the varying pattern of time that the lake was totally freezing up.According to the result of the lake ice duration, a comprehensive analysis on the trends and changes of Namco lake ice duration were taken combined with the annual mean temperature of Namco,area variation of Namco, the response to the climate events and other factors. The result shows that the duration of Namco lake ice has decreased by45-49days in which the totally freeze up time push back about23days and the time began to thaw bring forward about22days. We applied a significance test and cross wavelet transform analysis to find the relationship between the lake ice duration and the temperature in the region,the result shows a negative correlation between the two time series, but not dramatically.The result of corss wavelet transform indicate that the lake ice duration and the annual average temperature has significant correlation on5-6years scale,and we can infer from the result that the lake ice duration will increase slightly in the short future, but overall still showed a decreasing trend. The area of the lake which was calculated from Landsat data shows an increasing trend, In addition, the decreasing trend of lake ice duration in the corresponding period shows that both of them may be affected by the same climatic factors. In order to explore the response to the global climate events, we analyzed the response to ENSO in which the results show that there is a certain response to the El Nino and La Nina phenomenon,but the response is not strong in some years.The main innovation of this paper is that we put forward an algorithm to extract the lake ice parameters, and use the corss wavelet transform method to analyze the relationship between the lake ice duration and temperature.Meanwhile, due to the coarse resolution of passive microwave data, the accuracy of the NamCo Lake ice time parameters need to be further improved.