丁一汇,胡国权. 2003. 1998年中国大洪水时期的水汽收支研究[J]. 气象学报, 61(2):129-145, doi:10.11676/qxxb2003.014
1998年中国大洪水时期的水汽收支研究
A STUDY ON WATER VAPOR BUDGET OVER CHINA DURING THE 1998 SEVERE FLOOD PERIODS
投稿时间:2001-12-06  修订日期:2002-10-20
DOI:10.11676/qxxb2003.014
中文关键词:  1998年大洪水  势函数  流函数  水汽收支
英文关键词:1998 severe flood  Potential  Streamfunction  Water vapor budget
基金项目:《国家重点基础研究发展规划》(G1998040900)项目第一部分;国家自然科学基金项目(49794030)
作者单位
丁一汇  
胡国权  
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中文摘要:
      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1/3~1/2,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,来自南部边界(南海)的水汽大于来自西部边界的水汽。(4)南海季风爆发之后,由西边界经中印半岛输入南海地区的水汽明显增加,成为主要的水汽来源,并在南海地区形成一个明显的水汽源区,在此积累的大量水汽再进一步折向北输送到华南和长江流域,为那里的强降水提供必要的水汽供应条件。(5)长江流域大洪水期的强降水过程与水汽辐合的极大值密切相关。降水的强弱与水汽辐合的强弱变化一致,这表明后者是前者的一个必要条件。
英文摘要:
      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 it's south west water vapor flux becoming stronger are related to the potential being stronger in Indian Ocean.(2) At mospheric water vapor budget indicates that precipitation comes mainly from the convergence of water vapor and the convergence mainly in the lower at mosphere; 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 moist urefrom 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 more than from the west.(4) After South China Sea monsoon breaking out, the water vapor from west boundary through Indo-China Peninsula to South China Sea increases and becomes main water vapor source, therefore an obvious source is formed in South China Sea and the accumulative water vapor turns to north and transports to South China and Changjiang River Valley and affords t he water vapor condition for their strong rainfall.(5) The strong precipitation process during the Changjiang River Valley severe flood is well related to the max imum water vapor convergence, and the strong or weak precipitation is consistent with water vapor convergence, and this indicates that the latter is a necessary condition of the former.
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