1979-2016年我国东北地区空中水汽状况及变化趋势分析

水汽是形成云和降水的物质基础，与全球水分循环和能量平衡密切相关，对天气和气候具有重要影响。基于NCEP/NCAR月值再分析资料，综合分析我国东北地区上空不同高度层位比湿的气候学特征和长期趋势变化，同时分析了整层积分水汽通量的季节变化。结果表明：东北地区空中水汽集中分布于500 hPa以下，1979年至20世纪末低层比湿呈增加趋势，2000年后转为缓慢下降，但2012年以来波动回升。此外，东北地区比湿及水汽通量季节差异明显，夏季水汽含量最多，冬季最少，秋季多于春季；东北地区水汽含量最大值出现于7月，最低值出现在每年12月至次年1月。水汽来源受东亚季风系统影响明显，夏季水汽源地主要为南海，渤海和黄海对东北地区夏季水汽也有一定贡献；其他季节水汽主要来源于西风带输送。

Air moisture condition and change trend in Northeast China, 1979-2016

The water vapor in atmosphere is the material basis for formation of clouds and precipitation. It is closely related to the global water cycle and energy balance, and has an important impact on climate and weather. In this study, based on monthly reanalysis grid points (2.5°×2.5°) data within 1979-2016 from the NCEP/NCAR, the specific humidity, water vapor flux at 1 000 hPa of Northeast China are taken as the research object, quantitative at 1 000 hPa, 850 hPa, 700 hPa and 500 hPa. Based on the reanalysis of monthly NCEP/NCAR data, in this study, the climatic characteristics and long-term trend change of specific humidity at different altitudes over Northeast China have been comprehensively analyzed, as well as the seasonal changes of integrated water vapor flux. The results show that the vertical distribution characteristics of water vapor in Northeast China are that the water vapor content began to drop from 500 hPa level, the higher the elevation the lower the water vapor content. The specific humidity in Northeast China had showed an overall downward trend from 1979 to 2000. After 2000, an ascending trend has been seen. Spatially, in Northeast China there is a latitude effect significantly, the water vapor content is mainly concentrated in the south. In a year round the water vapor content in Northeast China is the maximum in July and the minimum is between December and January of next year. The sources of summer water vapor are mainly from the South China Sea, followed by the Bohai Sea and the Yellow Sea. In other seasons, westerly wind is the main source of water vapor.