西部调水下长期气候效应研究

Study on regional climate effect under water diversion in Northwest China

调水工程是优化配置水资源的战略措施,我国从1950年代就开始研究西部调水工程。然而,区域外调水的引入必将打破受水区原有的水热平衡,改变当地大气-陆面间的水分、能量交换过程,进而影响局地气候。因此有必要开展有关调水的区域气候效应研究。利用CMIP5中的全球气候模式MPI-ESM-MR输出结果作为区域气候模式RegCM4的初始场和边界场,研究在2021—2050年两种典型浓度路径情景下西北地区调水灌溉对区域气温、降水以及能量收支的影响。结果表明,大面积调水灌溉对全年的气温和降水均产生了影响,其影响在夏季尤为明显。具体来说,蒸散发在夏季明显增加(潜热通量增加35~45 W·m^(-2)),显热通量降低,导致夏季地温降低了近2℃。夏季降水增加主要在受水区及周边天山、祁连山和昆仑山等山脉附近,低空环流异常变化和对流上升运动增强为夏季降水的变化(增加0.5~1 mm·d^(-1))提供了动力条件,增加了受水区及周边高山地区的对流性降水潜力。此外,大面积调水灌溉使得该地区产生了复杂的大气环流变化,气象要素在600~925 hPa的垂直梯度发生了明显改变。

Water diversion project is a strategic measure to optimize the allocation of water resources.China has been studying water diversion project in the west since 1950s.However,the introduction of regional off-transfer water will inevitably break the original water and energy balance of the water demand area,change the process of water and energy exchange between local atmosphere and land surface,and then affect the local climate.Therefore,it is necessary to carry out water diversion of regional climate effect research.Using the output of MPI-ESM-MR global climate model in the CMIP5 as an initial and boundary conditions of RegCM4,the influence of temperature,precipitation and energy balance processes from 2021-2050 under two representative concentration pathways scenarios for water diversion irrigation in the northwest region in the future are analyzed.The results show that diversion irrigation has an effect on the annual temperature and precipitation,especially in summer.Specifically,evapotranspiration increased significantly in summer (latent heat flux increased by 35~45W·m^(-2)),and sensible heat flux decreased,resulting in a decrease of nearly 2℃in average surface temperature.The increase of summer precipitation is mainly in the vicinity of the study area and the surrounding Tianshan,Qilian and Kunlun mountains,etc.The abnormal change of low-altitude circulation and the enhancement of convective rising movement all provide dynamic conditions for the change of summer precipitation (an increase of 0.5~1mm·day^(-1)),and increase the convective precipitation potential of the water demand area and the surrounding alpine area.In addition,diversion irrigation caused complex atmospheric circulation changes in this area,and the vertical gradient of meteorological elements changed significantly at 600~925 hPa.