Passive microwave remote sensing of lake freeze-thaw over High Mountain Asia

Abstract

Lake ice is an important component of the hydrosphere and cryosphere, especially over high-lat itudes regions of High Mountain Asia (HMA), the long-term changes of freezing and thawing time can directly reflect the changes of climate. Remote sensing technology provides unreplaceable complement for HMA where the lake ice phenology is almost no monitoring, except that of Qinghai Lake. Considering the microwave signature's sensitivity to the snow and ice phase changes, a method based on the freezing and thawing probability were proposed. The long time series of Swath Brightness Temperature (TB) data from satellite-based passive microwave sensor AMSR-E (Advanced Microwave Scanning Radiometer for EOS) and AMSR2 (The Advanced Microwave Scanning Radiometer 2) were employed to retrieval the lake ice status of four lakes with different areas, Qinghai Lake, Siling Co, Hala Lake and Aqqikkol Lake. The method was validated with the result from higher resolution of daily cloud-free MODIS (Moderate Resolution Imaging Spectroradiometer) image, the result shows that, for four selected lakes, the R-Square of start of freeze-up(FUS) is 0.80466, end of freeze-up(FUE) is 0.92197, start of break-up(BUS) is 0.83882 and end of break-up(BUE) is 0.96127, respectively.