西北地区大气水汽含量时空分布及其输送研究

Spatial and temporal distribution and transportation of the water vapor in the northwestern China

利用ECMWF和NCEP/NCAR 1979—2016年逐月再分析资料,分析了我国西北地区大气水汽含量的时空分布及其输送特征。结果表明:(1)西北地区水汽含量在20世纪80年代中期至90年代末呈增多趋势,从90年代开始至21世纪初呈减少趋势。就季节而言,西北地区夏季水汽含量最多,占年平均水汽含量的46.6%。(2)西北地区水汽分布与降水分布具有一致性,水汽含量主要集中在西北地区东部及其西部的天山山脉、塔里木盆地东部一带,达12～30 mm,中部水汽含量较少,不足10 mm,水汽含量的空间分布呈现出"两边高中间低"的分布形式。(3)西北地区水汽输送以西风和季风两大环流系统为主,纬向西风水汽输送可达100～500 kg·m^(-1)·s^(-1),在全年水汽输送中占主要地位,夏季从印度洋来的强度可达100～200 kg·m^(-1)·s^(-1)的西南季风水汽输送对西北地区东部影响较显著。(4)西北地区水汽源主要位于新疆天山山脉、青海中东部、甘肃河西走廊中西段、宁夏和陕西北部等地区,而水汽汇则位于甘肃南部、陕西南部一带。

Based on the ECMWF and NCEP/NCAR re-analysis of the climate data during the 38 years（from 1979 to 2016）,the spatial and temporal distribution and the transportation of the water vapor in the northwestern China were analyzed.The results show as follows：（1） The water vapor content in northwestern China was increased from the middle 1980s to the late 1990s,but it was decreased after that.In terms of seasonal disparity,the water vapor content reached its maximum value in summer,accounting for 46.6% of the annual average water vapor content. （2） The spatial distribution of the water vapor in the northwestern China is in accordance with that of the precipitation in the form of ＂lower value in the middle and high values on both east side and west side＂ which meant that the water vapor was accumulated mainly in the east part of the region and in the Tianshan Mountains and east Tarim Basin in the west part of the region with its content being 12-30 mm,and there was less water vapor in the middle of the region with the content less than 10 mm. （3） The west wind and monsoon were the main carriers for the water vapor circulation in the northwestern China.The zonal westerly wind transferred the water vapor at 100-500 kg·m-1·s-1 which dominated the transportation of water vapor in a year.The southwest monsoon from the Indian Ocean in summer had a great effect on the water vapor transportation in the east of the region with a transport intensity being 100-500 kg·m-1·s-1. （4） The water vapor sources were primarily distributed in the Tianshan Mountains,the middle and east part of Qinghai Province,the middle and west part of Hexi Corridor,Ningxia Province and the north part of Shaanxi Province while the water vapor sinks were located in the south part of Gansu Province and the south part of Shaanxi.