Structure and mechanism of meso-scale low and heavy rainfall along the Baiu front

点击翻译按钮获取中文摘要

During the period from 21 May 2004 to 11 June 2004, we performed an intensive observation in the Miyako Islands and Okinawa Island using Doppler radars to observe heavy rainfall associated with a meso-scale low along the Baiu front. Many different types of precipitation systems were observed during the observation. Using the data of the radars, we investigated structures and processes of the precipitation systems. In particular, a detailed study was performed about the meso-scale low and associated precipitation observed on 7-8 June 2003 in the Miyako area. We found a characteristic wind structure with the precipitation system.Using the cloud-resolving model named CReSS (Cloud Resolving Storm Simulator), we performed a simulation experiment of the meso-scale low, the Baiu front, sub-synoptic low and associated precipitation. The development of meso-scale low within the sub-synoptic low along the Baiu front was successfully simulated by the CReSS model. Using the Earth simulator, a high -resolution simulation of the meso-scale low was performed. The result showed that the meso-scale low is one of the class of the multi-scale structure of the Baiu front and that cumulonimbus clouds are essentially important for the development of the meso-scale low.A heavy rainfall event occurred in Niigata and Fukushima prefectures on 12-13 July 2004. A data analysis indicates that the heavy rain occurred to the southeast of a meso-low formed along the Baiu front. Using the CReSS model, we performed a simulation experiment of the heavy rainfall and the Baiu frontal meso-scale low. An detailed analysis of the simulated result showed that a rainband developed within a highly humid region to the south of the meso-scale low and the maintenance for long time resulted in the heavy rainfall.