摘要
文中首先通过水汽通量的势函数和流函数的计算 ,分析了 1998年中国大洪水时期的全球水汽背景 ,然后从雨情分析入手 ,将 1998年 5～ 8月长江、松花江流域洪水期分为 7个降水阶段、11个区域 ,对各时段、各区域的水汽收支作了诊断分析 ,得到中国大洪水时期部分水汽收支图像 ,揭示了水汽循环的一些规律 ,主要结果如下 :( 1) 1998年 5～ 8月 ,中国东部地区是全球最强的水汽汇区 ,这与 1991年夏季的情况相似。水汽通量的势函数极小值区 (最大辐合区 )对应强降水区 ,并且暴雨区的水汽辐合是由半球尺度的水汽输送造成 ,这表明 ,即使对于区域性大洪水 ,它必须从极大范围地区获得水汽供应。分析还表明 ,南海季风的爆发及其区域内西南方向水汽流的增强与印度洋势函数 (水汽辐散 )的增强关系密切。( 2 )大气的水汽收支表明 ,降水主要来自水汽的辐合项 ,辐合主要发生在大气低层 ;用余差法计算出的局地蒸发项一般为降水量的 13 ～ 12 ,因而水汽的再循环过程也十分重要 ;垂直输送项把低层的水汽向中上层输送 ,增加高层的水汽积累 ,为积云的发展和潜热释放提供条件。( 3 )南海地区的水汽输送情况与中国强降水密切相关 ,南海季风爆发后 ,其强劲南风气流输送水汽的区域往往是强降水发生区。对于整个中国东部大陆区而言 。
By decomposing the water vapor transport vector into the sum of its nondivergent (rotational) and divergent (irrotational) components in terms of the streamfunction and potential, the water vapor background of the 1998 severe flood is investigated over the globe. Then, based on precipitation analysis, 7 precipitation periods and 11 regions are divided during May-August 1998 the severe flood periods over Changjiang and Songhua River Valley. After water budgets of all precipitation periods and regions are diagnosed , some schematics of water vapor budget are gained, the main results are as follows: (1) The East China is the strongest water vapor sink over the globe in May-August 1998.The minimum potential region (maximum convergent region) of water vapor transport vector corresponds to strong rainfall region, and the water vapor convergence of the heavy rain region is made by the hemisphere scale water vapor transportation, indicating that to regional severe flood it must gain water vapor from very large regions. The South China Sea monsoon breaking out and its southwest water vapor flux becoming stronger are related to the potential being stronger in Indian Ocean. (2) Atmospheric water vapor budget indicates that precipitation comes mainly from the convergence of water vapor and the convergence mainly in the lower atmosphere; The local evaporation (calculated by the residual) is generally 13～12 of the precipitation, so the water vapor recycle is also important; The vertical advection of the water vapor transports the moisture from the low to the middle and high layers and increases the high level moisture content, thus provides condition for the cumulus development and latent heat release. (3) The water vapor transportation in South China Sea is well related to the China strong rainfall.After South China Sea monsoon breaking out, the strong precipitation often occurs in the region whose water vapor gained by water vapor transportation from south. To East China, the water vapor from south boundary is mo
出处
《气象学报》
CAS
CSCD
北大核心
2003年第2期129-145,共17页
Acta Meteorologica Sinica
基金
<国家重点基础研究发展规划>(G19980 40 90 0 )项目第一部分
国家自然科学基金项目 ( 497940 30 )
