华北地区夏季水汽含量变化特征及影响因子

利用1979-2008年华北地区12个探空站的观测资料以及同期的NCEP/NCAR再分析资料，采用线性趋势、Mann-Kendall突变检验和合成方法，分析华北地区上空夏季水汽含量的时空演变特征以及影响水汽含量异常的大气环流等因子。结果表明：华北地区夏季水汽含量在空间上表现出由东南沿海向西北内陆随纬度增高而减少的分布特征，即东南部湿润、西北部干燥。近30 a华北地区夏季水汽含量整体上呈现出增加的趋势，其中在20世纪80年代末由少向多发生了明显突变。华北地区夏季水汽含量偏多（少）年，在南海至西太平洋地区有（无）明显的水汽向华北地区辐合，中纬度西风带有（无）水汽向华北地区输送，地表温度整体上偏高（低）。在500hPa高度场上，华北地区夏季水汽含量偏多年比偏少年副热带高压位置更偏西、强度更强。

Characteristics of water vapor content and its influencing factors in summer over Northern China

Based on the radiosonde data from 14 sounding stations and the NCEP/NCAR reanalysis data from 1979 to 2008 over the Northern China, the temporal and spatial distributions of water vapor content in summer and its in- fluencing factors such as circumfluence were analyzed using methods of a linear trend and a Mann-Kendall muta- tion test as well as a composite analysis. The results show that water vapor content decreases with the increase of latitude from the southeast coastal areas to northwest inland areas over the Northern China, namely, it is wet in the southeast and is dry in the northwest. On the whole, the water vapor content in summer is in a slightly increasing trend in recent 30 years, and it has an obviously abrupt change on the late 1980s. Whether or not there is obvious water vapor convergence to North China from South China Sea to the western Pacific and whether or not there is water vapor transportation to North China in westerly belt in middle latitude for the years when there is more or less water vapor content will lead to the surface temperature high or low on the whole. The location of subtropical high moves to westward and the intensity is stronger for the year when there is more water vapor content at 500 hPa height fields.