长江中下游地区旱涝异常的水汽输送结构特征及其变化趋势

本文采用箱格网整层水汽净收支及其边界流定量综合分析技术方案,分析了长江中下游旱涝过程中低纬间水汽输送结构特征及其年代际变化趋势.发现了中低纬西太平洋-南海区域存在副高变化显著区,且该区500hPa高度年际变化与东亚夏季风的强弱和中低纬间整层水汽输送结构特征以及长江中下游夏季降水密切相关.对东亚夏季风在中低纬关键区"箱格网"整层水汽输送收支距平状况的分析,发现长江中下游涝年夏季中低纬间呈反气旋式而旱年呈气旋式时水汽输送"相关链"结构,副高变化显著区500hPa高度距平序列与整层水汽输送的合成相关矢亦描述了上述长江中下游洪涝异常中低纬区间水汽输送反气旋式"相关链"图像.研究还表明20世纪80～90年代东亚夏季风减弱背景下,中低纬间反气旋式水汽输送"相关链"特征增强趋势显著,其与中国东部夏季降水年代际变化趋势吻合.

Characteristics of moisture transport in middle and lower reaches of Yangtze River and its variation trend

The structure of vapor transport and its decadal variation trend in the middle and lower reaches of Yangtze River in the processes of drought or flooding are studied by means of comprehensive analysis on whole layer moisture net budget and boundary flow of box web structure in atmosphere. It is found that there is a region with significant varying subtropical high pressure in West Pacific and South China Sea, which is located at low latitude area. The annual variation of the high pressure is closely related to the East Asian summer monsoon water vapor transport structure in mid low latitude area and precipitation in middle and lower reaches of Yangtze Riven. The analysis result of the deviation from average of whole layer vapor transport budget on boundaries of box structure at low mid latitude for weak or strong monsoon shows that an anticyclone or a cyclone type of vapor transport relation chain structure will appear correspondingly. The analysis also shows that the anticyclone type vapor transport correlation characteristic is obvious in 1980s to 1990s, in this period the summer monsoon is comparatively weakened. This tendency is consistent with the precipitation variation in these two decades.