水汽输送变化对天山山区气候增湿的影响研究

The Tianshan Mountains are the most vital and important areas for hydrological circle and water resources in the arid region of Northwest China. For the recent 50 years, wetting trend in this area is obvious, especially the frequency of heavy rainfall increased significantly. Interannual or interdecadal changes of water vapor transportation played important role to explain the reason of precipitation increasing. However, there had not been obvious progressed in diagnosis of water vapor transportation changing and How to influence the increase of precipitation in Tianshan Mountains. This application intend to explore the climate causes of rainfall increase in Tianshan Mountains from the angle of water vapor transportation changing. A new statistical method will be uses to replace the old one which mainly used monthly mean circulation. This new method focus on compound and trajectory analysis of the water vapor transportations using the history heavy rainfall processes avoiding the loss of valuable information by monthly average. On the basis of the above mentioned methods , according to assortments of influencing systems ,we will analysis the moisture transportation source, path, the vapor flux variation characteristics and corresponding circulation system during heavy rainfall periods, to determine quantitatively the contribution of each path of water vapor on the mountains precipitation. Meanwhile, consider of multielement of circulation driving force, to analysis the relationship between the space-time changing of water vapor transportation and precipitation increasing. The aim of this study is to get the image of structure characteristics of water vapor and precipitation from the muti-angle to reveal the influence mechanism of water vapor transportation changing on wetting trend in the Tianshan Mountains.

天山山区是西北干旱区最重要的水分循环和水资源关键区域之一。近50 年来天山山区气候增湿特征明显，降水显著增加，而水汽输送状况的年际或年代际变化对于研究降水增多的机理具有重要意义。但是,水汽输送状况变化的诊断以及如何影响天山山区降水增加却一直没有取得明显进展。本项目拟从水汽输送变化的角度研究天山山区降水增多的气候成因，通过改变以往用月、季平均水汽和环流场为主的统计方法，采用对历史逐次中度以上降水过程的水汽输送进行合成与轨迹分析，最大限度的突出水汽输送变化的信号。在此基础上，按照影响系统进行分类，分析降水过程时的水汽输送源地、路径、水汽通量的变化和相应的环流系统气候特征，定量确定各水汽路径对山区降水贡献的大小；同时，考虑环流动力等多种因素，分析水汽输送的时空变化与天山山区降水增多之间的联系，通过气候状态矢量，从综合角度反映水汽与降水之间的结构特征；最终揭示汽输送变化对天山山区气候增湿的影响。

天山山区是西北干旱区最重要的水分循环和水资源关键区域之一。近50年来天山山区气候增湿特征明显，降水显著增加，而水汽输送状况的年际或年代际变化对于研究降水增多的机理具有重要意义。本项目围绕增湿气候背景下水汽输送变化对天山山区气候增湿的影响机理问题，利用诊断分析和数值模拟的方法，研究了天山山区水汽输送变化特征及其大气环流调制水汽输送的动力学机制。天山山区降水、水汽和云水含量的分布主要受地形和海拔的影响，高值区在伊犁河谷，而降水、水汽和云水含量的低值区分布有明显差异，夏季以上要素均最丰富。垂直分布上，云液水含量高值在600hpa左右，云冰水含量的高值区则出现在500hpa左右，在对流层大气中云冰水含量值远大于云液水，且云冰水发展的高度较云液水更高。变化特征来看，天山山区降水、水汽和云水含量均有增加趋势，反映了天山山区的增湿现象。山区增湿具有明显的海拔依赖性，山区增暖明显加剧水循环，使得山区大气水汽含量增加，在动力条件下形成更多的降水。利用HYSPLIT后向轨迹模式，发现天山山区暴雨水汽主要主要来自700hPa，水汽输送路径有3条，其中偏北路径有2条，另1条为偏西路径；暴雨的水汽源地主要有三个，其中超过50%的水汽来自阿拉伯海以北—里海—巴尔喀什湖地区的水汽输送贡献，其次是波罗的海—北冰洋沿岸地区和鄂霍次克海以东地区。伊朗高压北抬与欧洲脊东移形成的乌拉尔脊叠加是暴雨过程的主导系统，中亚低涡东南移动形成强降水。同时，对流层高层的副热带西风急流和低层的偏东低空急流对强降水的水汽输送和辐合有重要影响。5月青藏高原地区地表热力异常差异与天山及其北部夏季降水有密切联系，当5月青藏高原视热源偏弱，其西北部地区偏强时，北疆上空盛行异常的偏南气流，有利于低纬度的暖湿气流北上，形成有利于降水的环流形势；印度半岛上空为异常反气旋环流，中亚上空为异常气旋环流，形成北疆夏季降水水汽的两步型输送，阿拉伯海水汽被输送至中亚和新疆北部地区。夏季降水和印度洋海温的有密切联系，随着阿拉伯海海温升高，加强了低纬度向中纬度的经向输送，配合中亚上空的气旋环流，将印度洋水汽进一步输送至中亚。