Meso-beta to -gamma-scale wind circulations associated with precipitating clouds near Baiu front observed by the MU and meteorological radars

During the Baiu season (17 June-8 July 1991) we carried out simultaneous tr opospheric observation by using the MU (Middle and Upper atmosphere) radar (VHF band, Kyoto University) and meteorological radars (C band of Osaka Met eorological Observatory, X band of Hokkaido University and C/Ku band of Kyo to University). Vertical distributions of three components of wind field an d precipitation particles were observed by the MU and C/Ku-band radars, res pectively. The C- and X-band radars were used to investigate horizontal dis tributions of precipitating clouds in the meso-alpha and -beta scales, resp ectively. Several meso-beta and -gamma-scale cloud systems were observed ar ound a meso-alpha-scale cyclone center during 4-5 July when rainfall was th e strongest in the whole observational period. They were divided into two g roups of convective clouds i) near a surface warm front and ii) near a surf ace cold front, and iii) one group of stratiform clouds on the north-wester n side of the surface cold front. In i), a remarkable updraft inside a prec ipitating cloud extending up to an altitude of la km was produced by a conv ergence (inflows coming from the front and rear of the precipitating cloud) at an altitude of 4-5 km anti by strong southerly wind in the middle tropo sphere. In ii), a narrow rainband with gust front was seen at the leading e dge of the surface cold front. Two meso-gamma-scale rotor circulations were found in front of and inside the rainband, respectively. In iii), south-ea sterly (north-westerly) ascent (descent) flows were observed above (inside/ under) the cold frontal surface extending up to an altitude of about 9 km. Below the cold frontal surface, there was a dry region without precipitatio n, and a part of the descending westerly flow returned to the Lack of the p recipitating cloud. In this study, vertical structures of meso-beta and -ga mma-scale cloud systems with characteristic wind flows as mentioned above w ere revealed by the detailed three components of wind field in both clear a nd precipitating atmosphere. They were presented as smaller cloud systems i n the hierarchical structure of cloud clusters near the meso-cu-scale cyclo ne in the central region of the Japan Islands.