(Table 1) Ice thickness at lake Nam Co, Tibet, during 2008-2009

Lake ice change is one of the sensitive indicators of regional and global climate change. Different sources of data are used in monitoring lake ice phenology nowadays. Visible and Near Infrared bands of imagery (VNIR) are well suited for the observation of freshwater ice change, for example data from AVHRR and MODIS. Active and passive microwave data are also used for the observation of lake ice, e.g., from satellite altimetry and radiometry, backscattering coefficient from QuickSCAT, brightness temperature (Tb) from SSM/I, SMMR, and AMSR-E. Most of the studies are about lake ice cover phenology, while few studies focus on lake ice thickness. For example, Hall et al. using 5 GHz (6 cm) radiometer data showed a good relationship between Tb and ice thickness. Kang et al. found the seasonal evolution of Tb at 10.65 GHz and 18.7 GHz from AMSR-E to be strongly influenced by ice thickness. Many studies on lake ice phenology have been carried out since the 1970s in cold regions, especially in Canada, the USA, Europe, the Arctic, and Antarctica. However, on the Tibetan Plateau, very little research has focused on lake ice-cover change; only a small number of published papers on Qinghai Lake ice observations. The main goal of this study is to investigate the change in lake ice phenology at Nam Co on the Tibetan Plateau using MODIS and AMSR-E data (monitoring the date of freeze onset, the formation of stable ice cover, first appearance of water, and the complete disappearance of ice) during the period 2000-2009.湖冰变化是区域与全球气候变化的敏感指示因子之一。当前学界在监测湖冰物候时多采用多源数据。可见光近红外（Visible and Near Infrared, VNIR）波段影像十分适用于淡水湖冰变化的观测，例如AVHRR与MODIS传感器获取的数据。主动与被动微波数据同样可用于湖冰观测，包括卫星测高、微波辐射计数据、QuickSCAT的后向散射系数，以及SSM/I、SMMR与AMSR-E传感器获取的亮温（brightness temperature, Tb）。现有研究多聚焦于湖冰覆盖物候，针对湖冰厚度的探究相对匮乏。例如Hall等人借助5 GHz（6 cm）辐射计数据，证实了亮温与湖冰厚度之间存在显著相关关系；Kang等人则发现，AMSR-E获取的10.65 GHz与18.7 GHz波段亮温的季节演化特征，受湖冰厚度的显著影响。自20世纪70年代起，学界已在加拿大、美国、欧洲、北极及南极等寒冷区域开展了大量湖冰物候相关研究。但针对青藏高原的湖冰覆盖变化研究却极少，目前仅公开报道过少量关于青海湖湖冰的观测成果。本研究的核心目标为：以2000-2009年为研究时段，利用MODIS与AMSR-E数据，监测青藏高原纳木错湖的结冰起始日期、稳定冰盖形成日期、首次无冰出现日期以及冰盖完全消融日期，以此探究该区域湖冰物候的变化特征。