【作者】 吴永萍；

【导师】 王澄海；

【作者基本信息】 兰州大学 ， 气象学， 2011， 博士

【摘要】 我国是一个缺水严重的国家,不仅人均占有水量低,水资源时空分布不均且往往与用水不协调,形成了严重的供需结构矛盾。一方面受季风气候影响,我国的水资源经常呈现阶段变化,导致严重的洪涝与干旱;另一方面,我国经济在迅速发展的同时也造成了水资源的严重污染,加剧了我国水资源短缺的局势。水生态失调已经成为制约我国可持续发展的瓶颈。目前,我国的水资源供应已经出现不安全迹象,未来全球变化背景下水资源的形势将更加严峻。新疆塔里木河是中国最长的内陆河,也是世界第二大内陆河(仅次于伏尔加河)。位于干旱的塔里木盆地北部,占地约1.02×106平方公里,是该地区生态、自然和各民族生存的生命线,因而被誉为“生命之河”,或“母亲河”。塔里木河流是环塔里木河流域的阿克苏河、喀什噶尔河、叶尔羌河、和田河、开都河—孔雀河、迪那河、渭干河与库车河、克里雅河和车尔臣河等九大水系144条河流的总称,流域总面积102×104kmm2(约106万平方公里),占我国国土总面积的9.41%。塔里木河干流全长1321km,自身不产流,依靠源流补给维系其生态环境。塔里木河流域三面环山,使得该地区水汽输送十分复杂,其机理也一直是个悬而未决的问题。长期以来,气候变化和人类对水土资源的过度开发导致平原地区河道断流,湖泊枯竭,土地沙化。该地区生态环境发生了明显变化,经济和社会可持续发展受到严重制约,直接影响着整个西部地区的生态安全。所有这些,在很大程度上取决于空中水资源和大气水循环的变化及其趋势。因此,为了进一步理解该地区水汽输送状况以及未来发展趋势,研究该地区的水循环机理显得十分重要和迫切。由于塔里木河流域地形十分复杂,且塔里木河流域地处塔克拉玛干大沙漠腹地,受西风控制且处于季风边缘,三面环山,被一个背对西风的U形大地形包围,形成了该地区独特而复杂的区域地理特征。但大地形、西风环流以及季风在区域气候形成中的相互关系尚不清楚。为此本文要解决的两个主要问题是：1)影响塔里木河流域水汽输送的多尺度环流与大地形的相互作用关系；2)气候变化对不同下垫面状况的局地水循环和降水的影响机理。本文选择塔里木河流域空中水汽、降水、湿度、风场、温压和DEM等资料,分析其在气候变化背景下的时空演化特征;对流域按不同的坡向、高程以及不同的下垫面状况进行对比分析,揭示进行气候变化对流域尺度水汽输送变化的驱动机理,即影响塔河流域水循环的多尺度大气环流系统的相互作用关系,以此为背景,研究典型区域内部水汽交换过程及其与降水特别是山区降水的关系,探索发生的原因,揭示气候变化对水循环的影响机理。主要的研究内容和结论如下：(1)塔里木河流域水汽输送时空演化特征。结果表明,塔里木上空水平方向为水汽汇,且纬向贡献大于经向；水汽的水平和垂直净收支均具有季节性变化,且夏季辐合为主,冬季辐散为主；水汽的水平输送和经纬向净输入量都表现为较一致的年际变化,且均在1970s年代中后期出现了较明显的年代际突变；在1978年到2003年全球变暖明显的时段内,水平方向水汽净输入量呈减少趋势。(2)塔里木河流域水汽通量散度时空演化特征。结果表明,塔里木河整个流域均表现为水汽的辐合,辐合中心位于塔里木河流域的南边,昆仑山北坡和帕米尔高原东交界处的盆地内和田河流域,其空间分布大致呈由西北到东南逐渐增加的趋势；整个对流层水汽的辐合主要集中在600hPa高度以下的对流层下层；在年代际变化上,20世纪60年代辐合量较大,20世纪70年代开始减小,到了20世纪80年代整个水汽辐合量有所增加,20世纪90年代又有所下降,21世纪初10年(近10年)有回升的趋势,但不明显。(3)塔里木河流域大气可降水量时空演化特征。结果表明,塔里木河流域上空大气可降水量在塔里木河流域腹地平原区域为相对高值区,四周的山区为低值区；降水量多年大气可降水量明显高于降水量少年,差值最大为2千克／米2,位于塔里木河流域腹地；塔里木河流域山区、平原以及整个流域大气可降水量年变化均呈现明显的季节性特征,全年可降水量的最大贡献为夏季,且最大值在7月,最小值在1月；在年代际变化上,山区与平原变化比较一致,在20世纪60年代中期到20世纪70年代中后期,大气可降水量出现了明显的下降趋势,其后的变化幅度相对减小。(4)塔里木河流域降水的时空演化特征。结果表明,塔里木河流域的降水主要呈现由东南向西北逐渐增大的空间分布形态；不同地区的降水量存在差异,山区总体大于平原,整个流域以天山南坡山区降水量为最多,昆仑山北坡平原地区最少；降水量随海拔高度的升高而增加,但在不同地区,降水量随高度的变率也不相同,与坡度和风向有关；整个塔里木河流域的山区和平原的降水量年际变化比较一致,但年代际变化差异较大,尤其是1987年到2003年全球气温显著增暖的期间,山区呈现明显的上升趋势,而平原则呈现基本不变甚至略有减小的趋势。(5)塔里木河流域降水转化率时空演化特征。结果表明,塔里木河流域山区降水转化率约为平原的7.7倍；山区和平原的降水转化率年际变化比较一致,相关系数为0.437,但两者年代际变化差异较大,尤其是在20世纪70年代后期到21世纪初,全球变暖较为明显的阶段,塔里木河流域山区的降水变化率呈现非常明显的增加趋势,而平原增加非常缓慢,几乎没有变化。(6)塔里木河流域多尺度大气环流的相互作用及其对水汽输送的影响。结果表明,影响塔里木河流域水汽输送水的主要大气环流因子包括：西风环流、NAO、ENSO及与之相关的东亚季风,主要的局地环境因子包括：U型大地形,内陆地理位置、植被分布等。由于西风环流和U型大地形的相互作用,使得塔里木河流域的水汽输送在对流层的上层和下层之间出现了转向,并影响了四边界的水汽输入量及其变化。另外,在ENSO、NAO以及东亚季风等的扰动下,西风环流的强弱发生非线性改变,并进一步影响塔里木河流域的水汽输送。在这些因子的综合作用下,塔里木河流域的水汽输送呈现以下特征：整个流域水汽净输入量的最大贡献为东边界,依次为北边界和西边界,南边界输入为负,这与传统的塔里木河流域的水汽输送以西方路径和西北路径为主的结论有所不同；在对流层上层,纬向和经向水汽净输入量之间存在负相关关系,西风环流主要影响纬向水汽净输入量；但在对流层下层,经纬向水汽净输入量之间存在非常显著的正相关关系。以上正是由于U型地形对水汽输送的转向作用导致的。(7)气候变化对塔里木河流域水循环的影响机理。结果表明,气候变化和人类活动导致了全球变暖,并使得全球大气环流发生改变；全球变暖加速了水循环,但不同尺度的水循环对气候变化的响应有所不同；由于海陆间水循环通过大气环流的变化来调整,局地水循环则受局地因子,如地表水资源、植被等的影响；从而使得塔里木河流域的水循环在山区和平原出现了不同的响应。可能由于中纬度大陆地区人类活动的加剧,使得中纬度地区增温幅度大于低纬地区,减小了中低纬度之间的热力差异,导致全球海陆间水汽运输减缓。这一变化直接导致塔里木河流域水汽净输入量以及空中水汽含量的减少。这对于地表水资源和植被都比较稀少的塔里木河流域的平原地区影响很大,并直接导致该地区降水量的减小,水资源匮乏。但对于山区影响不大,由于塔里木河流域山区具有丰富的地表水资源和茂密的植被分布,全球变暖直接导致该地区局地水循环的加速,并引起降水的增加。更多还原

【Abstract】 China is a country with heavy water shortage. Not only the per capita amount of water is low, but also the spatial and temporal distribution of water resource is uneven. The uneven distribution can not meet the needs well, and leads a conflict between needs and supplies. On the one hand, monsoonal climatology makes water resources chang periodically, which leads to severe droughts and floods; on the other hand, China’s rapid economic development has also caused serious pollution of water resources, it aggravates the situation of water shortage. The imbalance of hydroecology becomes a key factor that restricts the sustainable development of China. At present, some unsafe clues in Chinese water supply have appeared. It will be more serious for the water resource under global warming.Tarim River is the longest inland river in China and the second largest inland river in the world (second only to the Volga River). Situated in the north of the dry Tarim Basin, it is a lifeline safeguarding the economy, nature and the life of all ethnic groups in Tarim Basin. Therefore, it is crowned as "The River of Life", or "The Mother River".The Tarim River Basin (TRB) includes 9 main braches, which are the Akesu River, the Kashi River, YeerQiang River, Hetian River, Kaidu-Kongque River, Dina River, Weigan River, Kuche River, Keliya River and Cheercheng River, and 144 minor rivers. It has a watershed area of about 1.02 million sq. km., which is 9.41% of the area of China. The water mainly comes from the source rivers. Been surrounded by mountains, the water vapor transportation to this region is complicated and the the transportation mechanism also has been a pending issue. The climate change and overuse of water resource by human lead to the rivers cutout, the lakes dry up and the land desertification. The environment in this region has been changed a lot; the economy and society development are severely restricted, which causes the whole western ecosystem unsafe. All these results depend largely on the changes and the trends of the air water resource and atmospheric water cycle. Therefore, in order to understand better the situation of water transportation over this region and its future trend, it is important to study the local water recycle and the related land-sea water cycle.TRB locates in the middle of the Taklimakan Desert, with complicated terrain, controlled by westerly circulation and affected by the monsoon some times. It is surrounded by mountains, which is like a letter "U". The geological character over this region is unique and complicated. The effects of westerly circulation and monsoon in the formation of the climate over this region are unclear. Thus, two problems are to be investigated:one is the relation between large scale terrain and the multi-circulation of water vapor transportation over the TRB; the other is affecting mechanism of climate change on the water recycling over different land surface conditions.In this thesis, water vapor, humidity, wind, temperature and DEM (digital elevation model) data over the TRB are caculated and employed; their spatiotemporal evolutions under the climate change are analyzed; comparing analysis is also carried out among different slope direction, elevation and land surface condition. The possible physical mechanism of climate change on the watershed scale water vapor transportation (i.e. the multi-scale circulation interaction over the TRB) is investigated. Than, the relationship between the regional water recycling and mountain precipitation over typical regions is examined to find out the affecting regime of climate change on water cycles. The contents and conclusions are as follows:(1) The spatial-temporal evolution character of the TRB water vapor transportation. The results show that it is a water vapor sink in horizontal direction over the TRB, and zonal contribution is larger than meridional contribution. Horizontal and vertical water vapor net input shows a seasonal variation, it prevails convergence in summer while divergence in winter. Horizontal and vertical water transportations show consistent interannual variations and both have a notable interdecadal saltation. From 1978-2003, when the global warming is significant, horizontal water transportation in the region has a decreasing trend.(2) The spatial-temporal evolution character of the water vapor flux divergence over the TRB. The results show that the whole basin is a water vapor convergence zone. The convergence center locates on the south part of the TRB, near the northern slope of Kunlun Mountains and western of Hetian River Basin on the Pamirs Plateau. The convergence distribution shows an increases trend from northwest to southeast. The water vapor convergence occurs mainly under 600hPa. The amount of the convergence in 1960s are large, but decreases in the 1970s and increases in the 1980s. In 1990s, it decreases again and increases slightly in the first decade of the 21st century.(3) The spatial and temporal evolution of precipiatble water (PW) over the TRB. The results show that the high values of the PW are in the middle of the TRB. The low values are over the surrounding mountains. The PW in wet-years is large than that in dry-years. The largest difference between the wet-year and dry-year occurs in the middle of the TRB, with 2kg per sq.m. The PW over the whole Tarim regions have notable seasonal variations. The most PW contributes throughout the year is in summer; and the annual maximum occurs in July, the minimum occurs in January. The PW over mountains and plain have similar interdecadal variations, which is decreases significantly between the middle of 1960s and the late 1970s, than increases smoothly until 2009.(4) The spatial-temporal evolution of precipitation. The results show that the precipitation distribution shows an increasing trend from northwest to southeast over the TRB; precipitation is difference in various regions, the precipitation in mountains is larger than that in plains; over the whole basin, the maximum of precipitation is on the south slope of the Tianshan Mountains, while the minimum is on the north slope of the Kunlun Mountains; the precipitation increases with the altitude, but the increasing rates depend on the region. Mountain area precipitation changes in lines with the plain area precipitation interannually, but they have large difference in interdecadal variation. Especially, from 1987-2003, when it warms a lot, precipitation over mountains and plains changes inversely.(5) The spatial and temporal evolution of precipitation conversion efficiency (PCE). The results show that PCE in mountains is 6.7 times than that in plains. The interannual variation of PCE in both areas is consistant and the correlation coefficiency is 0.437. But there is a large difference in interdecadal variation, especially from the late 1970s to the early 21st century, when the globe warming is most significant, the precipitation changing rate increases significantly in mountains, while increases slightly in plains.(6) The interaction of multi-scale atmospheric circulation and its impact on water vapor transportation. The results show that the mainly circulation factors affecting the transportation includs the westerly circulation, ENSO, NAO and the related South Asia Monsoon. The main regional environment factors include the U-shaped terrain, the local distance from ocean. The interaction between the U-shaped terrain and the westerly circulation induces that the water vapor transportation turns between upper and lower troposphere and affecting the water vapor transport. In addition, under the impact of ENSO, NAO and South Asia Monsoon, the strength of westerly changes nonlinearly, which will further affects the water vapor transportation over the TRB.Influenced by these factors, water vapor transportation exhibits following characters:the Water Vapor Net Input (WVNI) of the eastern boundary contributed the most. Then the northern and western boundaries follow. The southern boundary export water vapor. This conflicts to the common knowledge that water vapor transportation over the TRB mainly along the west and northwest routines. Over the upper troposphere, zonal and meidional water vapor transportation correlated negatively. But they correlated positively over the lower troposphere.(7) The possible mechanism of the impacts of climate change on the water cycle and precipitation over the TRB. The results show that climate change and human activity causes the global warming and changes the general circulation; global warming accelerates the water cycle, but the response of different scale water cycle to climate change is different. At this point, the regional water cycle is affected by enviremantal factors such as land surface water resource and vegetation, which lead to different responds between mountains and plains over TRB. So, it is porssible that, due to the growing human activities, the amplitude of temperature in mid-high latitudes is larger than that in lower latitudes, which narrows the temperature difference between the middle and low latitudes. Thus, the water vapor transportation from ocean to land will decrease, which will directly leads to a decrease of water vapor transportation from outside to the TRB. Owing to the rare water resource and land surface vegetation over the plain areas, the decrease of water vapor import will affect considerably on the precipitation in plains. While over the mountains, there is dense vegetation and rich land surface water resource, the global warming will accelerate the water cycle and increase the precipitation.更多还原