Hierarchical structures of medium-scale cyclones and cloud clusters near the Baiu front observed by MU and meteorological radars: Outline and preliminary results of three-week observation campaign

We have carried out tropospheric observations by the MU radar (VHF-band) and meteorological radars (C-, Ku- and X-bands) for three weeks during the Baiu (early summer rain) season in 1991 (17 June-8 July). We produced a complete data set of three-dimensional wind velocity, turbulence parameters, cloud and precipitation with high reliability and resolution. Results of the data analysis show that a meso-alpha-scale cyclone on the Baiu front has an asymmetric hierarchical structure of vertical velocity fluctuation distributions, which consists of meso-beta-scale cloud clusters (with strong upward velocities and rainfalls) and meso-gamma-scale developing clouds (with remarkably strong events). Further, they are restricted by the lowest level of the stratiform turbulence near the tropopause and the frontal surface and are especially activated near the warm and cold fronts on the ground in the cyclone center.