Study on the diversity in the structure of the Meiyu front and the distribution of rainfall and cloud

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1. The formation process of the Meiyu frontal disturbance over China is different corresponding to its initial appearance location. That is, the meso-α-scale disturbance that formed in the eastern foot of the Tibetan Plateau causes heavy rainfall zone over the Yangtze River basin, while the cold northeasterly wind activates the Meiyu front over South China through the increase in temperature gradient.2. Though the distributions of height anomaly for the cases of both continuous southward migrating and stationary heavy rainfall zone over China indicate EU pattern-like teleconnection, the location of positive and negative anomaly is different between respective case. As for the former case, negative height anomaly locates in the East China Sea, which causes the southeastward retreat of the Subtropical High and the incursion of cold airmass into the Yangtze River basin from the Japan Sea. Airmass to the north of the Meiyu front of this case is rather cold and the frontal system indicates vertically higher structure. Concerning the latter case, height field over Southern China dose not decrease and the Subtropical ridge remains there. Since the cold northeasterly is restricted to the northern Japan Sea, negative temperature anomaly around the Meiyu front is not observed except in the lower layer.3. The structure of rain-producing cloud (convective/stratiform cloud) in the Baiu front around Japan could vary according to the characteristics of the frontal zone. In case the Baiu front corresponds to the Eurasian Polar frontal zone., rainfall from the stratifrom clouds preveils. On the contrary, convective rainfall prevails under the Baiu front that prolonged from China with cold airmass to the north of the front4. Contribution of daily rainfall amount to total rainfall amount during the Baiu season is investigated to clarify the geographical and year-to-year difference in the statistical feature of rainfall intensity over Japan.