青藏高原湖冰物候的时空变化及其影响因素

为明确青藏高原湖泊湖冰物候信息及其对气候变化的响应,以青藏高原面积较大(面积100 km2)的40个湖泊为研究对象,利用MODIS数据,采用阈值法提取湖冰物候,分析2000—2015年青藏高原湖冰物候的时空变化规律及其影响因素.结果表明:青藏高原湖泊开始结冰在11月初—12月中旬,完全结冰在11月中旬—次年1月初,开始融化在3月中旬—5月初,完全融化在4月中旬—6月初,封冻结冰期176 d左右,完全封冻期130 d左右.湖冰物候有明显区域差异,北部湖区开始结冰期早,完全融化期晚,封冻期长;南部湖区开始结冰期晚,完全融化期早,封冻期短.2000—2015年,大部分湖泊湖冰物候变化趋势不显著.北部湖区封冻期和完全封冻期波动较大,而东部和南部湖区完全封冻期变化程度小.湖冰物候时空变化主要受温度、降水、风速的影响,温度是主要的影响要素,温度升高或降雨增加都会使封冻期缩短,风速对湖冰物候有一定的影响.

Temporal and Spatial Variation of Lake Ice Phenology and Its Influencing Factors in the Tibetan Plateau

To clarify the lake ice phenology of the Tibetan Plateau and its response to dimate change, taking 40 lakes with larger area ( >100 km2 ) in the Tibetan Plateau as the research subject, using threshold method with MODIS10 data, the phenology of lake ice in the Tibetan Plateau was obtained from 2000 to 2015 , and the spatial-temporal variations of lake ice and its relationship were analyzed with climate change. Results show that the freeze onset ( FO) of lakes ice generally appears in early November to mid December, the freeze up ( FU ) of lakes ice appears in the middle of November to the early January of next year, the break onset ( BO) of lakes ice appears in the middle of march to early may, and the break up ( BU) of lakes ice appears in the middle of April to early June. The mean ice duration ( ID) are 176 days, the mean completely ice duration ( CID) are around 130 days. There are obvious regional differences in the lake ice phenology of the Tibetan Plateau, the FO of the north lakes is the earliest, the BU of the north lakes is the latest, and the ID of the north lakes is the longest;the FO of the south lakes is the latest, the BU of the south lakes is the earliest, and the ID of the south lakes is the shortest. The trend of lake ice phenology change of most lakes is not significant. CID and ID change is large in northern lakes, CID and ID change is small in the southern and eastern lakes during 2000—2015. The temporal and spatial changes of lake ice phenology are mainly affected by temperature, precipitation and wind speed. The temperature is the main influence factor, the increase of the temperature and rainfall will cause the freezing period to be shortened, and the wind speed has a certain impact on the lake ice phenology.