2000-2014年黄河源区ET时空特征及其与气候因子关系

黄河源区地处青藏高原东缘,具有独特的自然生境和丰富的自然资源,是中国西南区域经济发展的重要生态安全屏障。以MODIS ET产品作为研究黄河源区地表蒸散发（ET）的数据源,结合黄河源区内部及周边18个气象站数据、全国1∶100万植被类型图和黄河源区DEM数据,利用趋势分析、相对年际变化和相关分析法,研究2000-2014年黄河源区ET时空变化特征及不同土地利用类型下ET的变化规律,重点探讨了ET与气候因子的关系。结果表明：① 黄河源区多年ET区域分异规律明显,北部ET显著弱于中部和东南部,最强ET位于黄河源区的东南部,多年平均ET值为538.61 mm/a,距平相对变化显著,ET年际变化呈先减小后增加的趋势,平均趋势变化率为0.44 mm/a;② 年内ET呈周期性单峰变化趋势,7月达到峰值;2000-2014年黄河源区多年四季ET季节性差异明显,夏季ET最强达到188.14 mm/a,春秋季次之,冬季ET最弱仅97.15 mm/a;③ 研究时段内不同土地利用类型的ET大小表现为沼泽地>林地>草地>其他>裸地,整体上各土地利用类型的ET呈逐渐增加趋势;④ 相关分析结果表明,ET与同期气温、降水呈正相关关系,与相对湿度呈负相关关系,其中降水对ET的影响强于气温;驱动分区结果显示黄河源区ET受气候因子驱动的地区主要表现为降水驱动。

Spatio-temporal characteristics of evapotranspiration and its relationship with climate factors in the source region of the Yellow River from 2000 to 2014

Located at the eastern margin of the Tibetan Plateau, the source region of the Yellow River is an important ecological security shelter for economic development in Southwest China, with its unique natural habitats and abundant natural resources. Based on the data of 18 meteorological stations within and around the source region, map of China vegetation types (1:1000,000) and DEM data, and using the methods of trend analysis, relative inter-annual variation and correlation analysis, we selected MODIS evapotranspiration (ET) as the main data source to research the spatio-temporal characteristics of ET and its variation under different land use types as well as its relationship with climate factors in the study area from 2000 to 2014. The results indicate that: (1) the regional differentiation of mean ET over years is obvious, the northern ET is significantly weaker than that of the central and southeastern parts, and the strongest ET is observed in the southeastern part. The multi-year mean value of ET is 538.61 mm/a, and the anomaly relative variation is obvious. In addition, the trend of inter-annual variation of ET decreases firstly and then increases, and the trend variation rate is 0.44 mm/a. (2) During the study period, the ET shows a periodic unimodal trend and peaks in July. Moreover, seasonal differences of ET are apparent in the source region of the Yellow River, and the highest value of ET reaches 188.14 mm/a in summer, followed by spring and autumn, yet the lowest is only 97.15 mm/a in winter. (3) From 2000 to 2014, the value of ET in different types of land use has a similar regular pattern, namely: wetland > forest > grassland > other types > bare land. On the whole, the value of ET in each type of land use increases gradually. (4) According to the correlation analysis results, there are positive correlations between ET and air temperature, as well as between ET and precipitation, while ET has a negative correlation with relative humidity. The effect of precipitation on ET is stronger than that of air temperature. Furthermore, the result of ET driven by different factors demonstrates that the climate-driven region of ET is predominantly precipitation-driven in the source region of the Yellow River.