近55年三江源地区地表干燥度时空变化特征及其对气候因子的响应

Characteristics of Temporal and Spatial Variations of Surface Aridity Index and Climatic Factors on the Impact in Headwaters of the Three Rivers in Recent 55 Years

三江源地区是我国乃至亚洲的重要水源地。了解该区的干湿状况对水资源科学管理、生态环境保护、保障中下游水资源供给量和水安全具有重要的意义。基于三江源地区1960─2014年13个气象站点逐日气象资料,采用Penman-Monteith模型和泰森多边形法计算出潜在蒸散和降水量的比值,得到干燥度指数(AI),并以气候倾向率、滑动t检验、累积距平法、DEM修正、经验正交函数(EOF)分析了近半个世纪以来该区地表干燥度的时空变化特征,同时利用灰色关联法分析气候因子对其影响强度。结果表明,(1)近55年三江源地区地表干燥度以-0.056/10 a(P<0.05)的速率降低,长江源区下降幅度最大为-0.075/10 a(P<0.05),其次为黄河源区、澜沧江源区,分别为-0.03/10 a、-0.024/10 a。(2)三江源地区、长江源区、澜沧江源区、黄河源区平均气温分别以0.3℃/10 a(P<0.001)、0.3℃/10 a(P<0.001)、0.35℃/10 a(P<0.001)、0.25℃/10a(P<0.001)的速率呈上升趋势,并均在1998年(通过0.05显著性水平)发生突变。(3)三江源区和长江源区地表干燥度均在1996年(通过0.05显著性水平)发生突变,澜沧江源区突变时间不确定,黄河源区在2004年(通过0.05显著性水平)发生突变;即1996年后三江源地区逐渐趋于暖湿化。(4)季节变化特征差异明显,冬半年干燥、夏半年湿润,冬季变化趋势最大且达到-2.59/10 a,其次为春季、秋季、夏季,分别为-0.72/10 a(P<0.05)、-0.05/10 a、-0.02/10 a。(5)三江源地区地表干燥度的空间分布与地形关系密切,海拔高的地区干燥,海拔低的地区湿润;由东南向西北逐渐增高,以巴颜喀拉山为界,东湿西干,南部有增加趋势而北部有降低趋势。(6)1990年前气温对地表干燥度的影响占主导,1990年后气温、风速和日照时数对其影响最为显著。

Headwaters of the Three Rivers which is known as the “Chinese water tower” is an important water source in China andAsia. Understand the area of dry and wet conditions is vital to scientific management of water resources, ecological environmentprotection, ensure the river of water supply and the safety of water. Characteristics of Temporal and Spatial variations of SurfaceAridity Index （AI） in Headwaters of the Three Rivers is analyzed by the methods of climate trend rate, the cumulative departure,correct of DEM and Empirical orthogonal function, at the same time, the strength of the impact on climate factors is used by methodof Grey Correlation. AI which defined as a ratio of potential evapotranspiration and precipitation, the potential evapotranspirationand precipitation were computed by using FAO Penman-Monteith model and Thiessen Polygon method, on the basis of 13meteorological stations daily weather data from 1960 to 2014. The results show that： （1） In recent 55 years, the surface aridity indexwas reduced at a rate of -0.056/10 a （P〈0.05） in Headwaters of the Three Rivers, declined in the Yangtze River reached a maximumof -0.075/10 a （P〈0.05） and then the Yellow River, Lancang River reached -0.03/10 a, -0.024/10 a, respectively. （2） All ofHeadwaters of the Three Rivers, the Yangtze River, the Lancang River and the Yellow River average temperature were increased andmutated in 1998 （pass the significance level of 0.05）, the rate of temperature reached 0.3 ℃/10 a （P〈0.001）, 0.3 ℃/10 a （P〈0.001）,0.35 ℃/10 a （P〈0.001）, 0.25 ℃/10 a （P〈0.001）, respectively. （3） Mutation of AI in 1996 （pass the significance level of 0.05） inHeadwaters of the Three Rivers and the Yangtze River, the mutation time of the Lancang River is uncertain, the Yellow Rivermutated in 2004 （pass the significance level of 0.05）; which is tended to warm and humid after 1996 in Headwaters of the ThreeRivers. （4） Seasonal variation has significantly different, winter months in dry and summer months in humid, the biggest trends inwinter and reached -2.59/10 a, followed by spring, autumn, summer are reached -0.72/10 a （P〈0.05）, -0.05/10 a, -0.02/10 a,respectively. （5） The spatial distribution of surface aridity has closely contact with terrain, high altitude areas tend to dry, low altitudeareas tend to moist; the value generally increased gradually from southeast to northwest, bounded by the Bayan har mountain, wet ineast and dry in west, the south has increased trends but the opposite of north. （6） The temperature dominated on surface aridity before1990 s, after that temperature, wind speed and sunshine were the most significant influence on it.