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

Utilizing the surface data of 39 stations and radio sonde 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/m2 and 132.3W/m2 in the unstable condition, respectively, and -1.5W/m2 and -2.5W/m2 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.