西北干旱区是对全球变化响应最敏感地区之一,研究分析全球变暖背景下的西北干旱区水资源问题,对应对和适应未来气候变化带来的影响具有重要意义。本文通过对西北干旱区气候变暖影响下的水资源形成、转化与水循环等关键问题最新研究成果的总结分析,得出如下结论：(1) 西北干旱区温度、降水在过去的50年出现过“突变型”升高,但进入21世纪,温度和降水均处于高位震荡,升高趋势减弱;(2) 西北干旱区冬季温度的大幅升高是拉动年均温度抬升的重要原因,而西伯利亚高压活动和二氧化碳排放是引起冬季升温的重要影响因素;(3) 西北干旱区蒸发潜力在1993年出现了一个明显的转折变化,由显著下降逆转为显著上升的趋势。气候变暖、蒸发水平增大对西北干旱区生态效应的负作用已经凸显;(4) 西北干旱区冰川变化对水资源量及年内分配产生了重要影响,部分河流已经出现冰川消融拐点。在塔里木河流域,冰川融水份额较大 (50%),可能在未来一段时期,河川径流还将处在高位状态波动。全球气候变暖在加大极端气候水文事件发生频率和强度的同时,加剧了西北干旱区内陆河流域的水文波动和水资源的不确定性。

The arid region of Northwest China is a special natural unit, which responds sensitively to the global climate change. Studies on the impact of climate change on water resources in the arid region of Northwest China have a significant effect on the adaptability of future climate change. Based on the latest research results, this paper analyzes the impacts of climate change on the formation and transformation of water resources and water cycle in the arid region of Northwest China. The results can be shown as follows: (1) The air temperature and precipitation in the arid region of Northwest China had a significant increasing trend in the past 50 years, however, the sharp increasing trend has retarded since the 21st century. (2) The temperature change in winter could be the most important factor for the unusually sharp rise in annual air temperature in this region. Moreover, the Siberian High and carbon dioxide emissions could be the most important reasons for the higher rate of the winter temperature rise. (3) Pan evaporation in the region exhibited an obvious decreasing trend until the early 1990s (1993), however, the downward trend reversed to go upward since 1993. The negative effects of warming and increasing evaporation on ecology have been highlighted in the arid region of Northwest China. (4) The glacier change has exerted great impact on water resources and its annual distribution in the arid region of Northwest China, and many rivers have passed the "Glacier inflexion". In the Tarim River Basin, the proportion of glacier melt water to runoff is high (e.g., as much as 50%) and it is supposed that the runoff may show a great fluctuation in the near future. Global warming not only increases the frequency and intensity of hydrological extremes, but also intensifies the fluctuation and uncertainty of inland rivers.

Temperature and precipitation time series datasets from 1961 to 2005 at 65 meteorological stations were used to reveal the spatial and temporal trends of climate change in Xinjiang, China. Annual and seasonal mean air temperature and total precipitation were analyzed using Mann-Kendall (MK) test, inverse distance weighted (IDW) interpolation, and R/S methods. The results indicate that: (1) both temperature and precipitation increased in the past 45 years, but the increase in temperature is more obvious than that of precipitation; (2) for temperature increase, the higher the latitude and the higher the elevation the faster the increase, though the latitude has greater influence on the increase. Northern Xinjiang shows a faster warming than southern Xinjiang, especially in summer; (3) increase of precipitation occurs mainly in winter in northern Xinjiang and in summer in southern Xinjiang. Ili, which has the most precipitation in Xinjiang, shows a weak increase of precipitation; (4) although both temperature and precipitation increased in general, the increase is different inside Xinjiang; (5) Hurst index (H) analysis indicates that climate change will continue the current trends.

利用西北地区22个代表站1951-1998年逐月降水量资料,用气候趋势系数和滑动t检验两种方法,研究了该地区降水量年代际尺度的变化趋势。结果表明:近半个世纪以来,西北大部分地区秋季趋旱,高原东北侧降水呈减少的趋势,近10a来,这种减少趋势更为严重。其中,高原东北侧南部比北部干旱化的趋势更为明显。这是近10a来天水重旱的年代际尺度的背景。80年代中西北秋季降水突变减少。

The trends and interannual variation of precipitation in Northwest China are studied by using the trend coefficient and moving t-test technique based on the(1951-1998) observation data at 22 stations located in the Northwest Region of China. The results show that there exists descending trends of precipitation on the northeast side of Qinghai-Xizang Plateau during recent half a century, especialy during recent 10 years.

以叶尔羌河流域源区为例,选取塔什库尔干气象站的气温数据和库鲁克栏杆站的洪水资料,基于Copula函数对洪峰流量和1、3、7 d洪水总量的概率分布特征进行分析,结合小波相干分析进一步探讨气候因子变化与洪水极值事件的关系。结果表明:两变量的同现重现期>单变量重现期>两变量的联合重现期,联合重现期和同现重现期随着洪峰流量和洪量的增大而变长,相应洪水极值事件发生概率降低;夏季日平均气温和洪峰流量序列在年代际尺度上具有高相干性,夏季日平均气温先于洪峰流量0.13~0.31周期变化;基于Copula函数建立1957—2010年夏季日平均气温与洪峰之间的二维统计模型,单变量重现期越长,所对应两变量的联合重现期与同现重现期之间相差越大;随着夏季日平均气温的升高,不同重现期洪水发生的可能性均增大。研究成果可对该地区的洪水风险管理和水资源适应性对策提供重要的科学价值和技术支撑。