1991年江淮暴雨期地气通量与混合层结构的研究

A STUDY OF THE SURFACE FLUXES AND STRUCTURE OF MIXED LAYER DURING THE MEIYU RAINFALL OVER THE YANGTZE HUAIHE RIVER BASIN IN 1991

本文用１９９１年５—７月江淮及其北部地区的地面与高空资料根据３种不同的整体公式对地表通量（动量、感热和潜热通量）进行了估算，并对混合层结构进行了研究，揭示出这次持续性特大暴雨中陆面过程的一些特征，主要结果如下：１．地表通量依赖于大气稳定度，稳定度越强，地表通量越小。不稳定状况下平均地表动量通量为０．０１５４Ｎ／ｍ２，向上的感热和潜热平均值分别为２５．７Ｗ／ｍ２和１３２．３Ｗ／ｍ２；稳定状况下，地表动量通量为０．００６Ｎ／ｍ２，感热和潜热通量平均是向下输送的，分别为－１．５Ｗ／ｍ２和２．５Ｗ／ｍ２。２．地表通量与降水过程密切有关。雨期的动量通量略小于非雨期，而雨期的感热与潜热通量明显小于非雨期，雨量越大，这两种通量愈小。３．地表通量具有明显日变化。动量、感热和潜热通量的最大值出现在下午２时左右，最小值出现在凌晨２时左右。４．混合层与雨期关系密切，雨期的混合层高度较非雨期低，这时地表感热和潜热通量小；

Utilizing the surface data of 39 stations and radiosonde data over the Yangtze Huaihe River Basin from May to July in 1991, the surface fluxes were estimated with three different bulk schemes, and the structure of mixed layer was investigated. The major results are as follows: (1)The surface fluxes depend on the atmospheric stability. The stronger the degree of stability is , the smaller the fluxes are. The mean sensible and latent heat fluxes amount to 25.7W/m 2 and 132.3W/m 2 in the unstable condition, respectively, and -1.5W/m 2 and -2.5W/m 2 in the stable condition, respectively. (2)The surface fluxes have a good relationship with rainfall episodes, with the later having smaller surface fluxes. (3)The surface fluxes assume a significant diurnal variation, with the maximum transport observed around 14h(BT) and the minimum transport around 02h(BT). (4)The level of mixed layer is lower and turbulence is weaker during rain period than during no rain period. The degree of mixture depends on potential stability. The bigger the potential stability is , the smaller the degree of mixture is. The higher the level of mixed layer is, the more the transport of sensible and latent heat fluxes are.