A purpose of this study is to clarify characteristics of convective boundary layer (CBL) and vertical circulation in the CBL over the Huaihe River Basin during early summer in 2004. The Huaihe River Basin has a large plain in which farmland is nearly uniform and flat, and double cropping (wheat and rice) is cultivated annually. In early summer, the vegetation change from mature wheat fields to paddy fields.

Firstly, the data observed by 1290 MHz wind profiler radar (WPR) and 30 m flux tower was analyzed. In the fomer period which vegetation was mature wheat fields or bare fields, sensible heat flux (SHF) from land surface was narly equal to latent heat flux (LHF). In the latter period which vegetation changed to paddy fields, LHF was much larger than SHF. ``Dry-case'' as a representative of the fomer period and ``wet-case'' as that of the latter period are defined, and two fine days are selected for my analyses. On the dry-case, a deep CBL corresponding to large SHF developed rapidly from early morning. Thermal updrafts in the CBL were strong. On the wet-case, a shallow CBL corresponding to small SHF developed slowly from late morning. Thermal updrafts in the CBL were weak. The circulation formed by thermal updrafts and inter-thermal downdrafts was detected only below the height of the CBL top, therefore the circulation on the dry-case was higher than that in wet-case. However vertical motion profiles averaged from 13 to 15 LST on the dry-case can not be explained by random thermal updrafts. The time-mean vertical motion was positive value from surface to the middle of the CBL, and was negative value near the CBL top.

Secondly, numerical simulation using the CReSS (Cloud Resolving Storm Simulator) is conducted in order to investigate three-dimensional structure including temperature and humidity, and to evaluate vertical flux caused by the circulation. The surface heat flux and the development of the CBL on both cases were reproduced adequately. In the middle of the CBL on the dry-case, roll-convection which aligned parallel with the mean horizontal wind was formed. The vertical motion profiles observed by WPR were explained by the updraft region of the roll-convection. Vertical heat and moisture fluxes in the CBL were estimated. On the dry-case, the heat flux contribute to almost all of the buoyancy flux. On the wet-case, in contrast, the contribution of the moisture flux was equaled to that of the heat flux. Large contribution of the moisture flux to the buoyancy is the characteristics of the CBL in humid continental area.