利用被动微波探测青海湖湖冰物候变化特征

Detecting changes of ice phenology using satellite passive microwave remote sensing data in Qinghai Lake

湖冰物候是气候变化的敏感因子,不仅能反映区域气候变化特征,还可以反映区域气候与湖泊相互作用。利用长时间序列(1978—2018年)被动微波遥感18GHz和19GHz亮度温度数据、MODIS数据(2000—2018年)、实测湖冰厚度数据(1983—2018年)和气温、风速、降水(雪)数据(1961—2018年),分析青海湖湖冰变化特征及其对气候变化的响应。结果表明:青海湖流域呈现显著的变暖趋势(1961—2018年),气温上升2.85℃,在这种气候条件下,青海湖湖冰封冻日推迟(0.23d·a^(-1)),消融日呈现明显的提前趋势(0.33d·a^(-1)),湖冰封冻期天数明显减少,减少速率为0.57d·a^(-1);同时,湖冰厚度以0.29cm·a^(-1)的速率减薄。此外,总结归纳了青海湖冻结-融化空间特征,青海湖主要由东部海晏湾地区开始冻结,从西部黑马河等地区开始消融,冻结和消融过程存在空间差异。通过分析湖冰冻融特征和气候因子关系发现,青海湖流域冬季气温是影响青海湖湖冰物候变化的主要因素,同时风速和降水(雪)也是影响湖冰发育和消融的重要因素。

Lake ice phenology is a sensitive factor of climate change,reflecting not only characteristics of regional climate change,but also interaction between regional climate and lake.In this study,long-term time series(1978—2017)of satellite passive microwave remote sensing data,MODIS data and ground-based measured lake ice data(1983—2017),air temperature precipitation/snowfall data(1961—2016)were used to analyze the phenology changes of Qinghai Lake ice and its climate control.Results showed that Qinghai Lake basin showed a significant warming trend(1961—2018)and temperature rises by 2.85℃.Under this climatic condition,Qinghai Lake ice on day was delayed(0.23 d·a^(-1)),and initial melt day illustrated an obvious advanced trend(0.33 d·a^(-1)),ice cover duration demonstrated significantly reduced trend,and reduction rate was 0.57 d·a^(-1).Meanwhile,lake ice thickness was reduced at a rate of 0.29 cm·a^(-1).In addition,the characteristics of freezethaw space of Qinghai Lake were summarized,Qinghai Lake was mainly frozen by eastern Haiyanwan area,ablation began from the western Heimahe area.There are spatial differences in freezing and ablation processes.By analyzing the relationship between freezing and thawing time characteristics of lake ice and climatic factors,winter temperature in Qinghai Lake Basin is the main factor affecting ice phenology.At the same time,wind speed and precipitation(snow)are also important factors affecting the formation and ablation of lake ice.