2000—2014年东非断裂带湖泊群面积变化时间序列分析

Surface Lake Area Variation Monitoring and Time Series Analysis of East African Great Rift Valley

针对使用单一遥感数据源对地表湖泊进行面积变化分析时难以建立完整的面积变化时间序列遥感数据库、难以获取非遥感辅助数据进行有效集成等问题,提出了对地表湖泊年际、年内面积动态变化的时间序列分析方法。建立2000—2014年湖泊面积变化及其流域内降雨、蒸散发变化的时间序列遥感数据库,在相同的时间序列下,分析了湖泊面积年际变化规律及其与降水和蒸散发等气候要素之间的关系,选取了变化较为明显的单个湖泊流域单元,全面分析其年内季节性变化规律及其与降水和蒸散发之间的关系。分析表明,在2000—2014年间,湖泊面积明显萎缩,流域内降雨量的年际变化直接导致湖泊发生相应的年际面积波动,流域内地表蒸散发的年际波动从侧面反映了湖泊群年际变化规律。

Due to water scarcity, analyzing the current situation of the water resource and monitoring its dynamic changes through remote sensing have practical significance for Africa. It is difficult to establish a complete time series database and make full use of the non-remote sensing data by a single remote sensing data source. With the aid of MODIS NDVI products （MOD13） ,a 15-year （2000-2014）lake surface area dataset of the middle part of the valley was obtained by a combined method of band ratio and threshold segmentation. In the same time series, based on the TRMM/3B43 product and the MODIS ET product （MOD16） ,information of rainfall and the terrestrial evapotranspiration was obtained. Further, their spatial distribution and their annual and interannual fluctuation were analyzed. Finally,the characteristic of the lake area variation was depicted and its relationship to the climatic factors such as the rainfall and the terrestrial evapotranspiration was discussed, respectively. The results revealed that the lakes with different area magnitude in the study area,occupying 80.64% of the total surface lake area across the African continent,had a tendency of decrease between 2000 and 2014. The rainfall in the study area also decreased drastically in the same time series and had variation regularity which reflected the climate model in the East African Great Rift Valley. The comprehensive analysis of the annual variation of rainfall, terrestrial evapotranspiration and lake area demonstrated a coincident changing pattern which indicated the climatic factors had significant effect on the lake surface area change in the study area.