Mei-Yu (Baiu in Japan) is a weather and climate phenomenon in the area of Japan, Taiwan, and subtropical China where the seasonal rainfall distribution reaches a peak in late spring and early summer due to the repeated occurrence of the Mei-Yu front. From the satellite pictures, the Mei-Yu front is usually accompanied by a nearly continuous cloud band with organized mesoscale convective systems (MCSs). To the south of the Mei-Yu front, a low-level jet (LLJ) is often observed and is closely related to the formation of MCSs and heavy rainfall events. As the Mei-Yu front approaches Taiwan, the front and the accompanying MCSs and LLJ tend to be affected by the mesoscale topography of Taiwan, the Central Mountain Range (CMR). Besides, the land-sea contrast coupled with island topography produces the land-sea breeze, the mesolow, and the island circulations which are important in modulating the local precipitation.
In this paper, an overview of the current understanding of the structure and dynamics of the mesoscale features observed in the Taiwan Mei-Yu season is presented. Research results in the pre-TAMEX era as well as those derived from TAMEX program are discussed for the Mei-Yu front, the LLJ, the MCSs, the mesolow, the land-sea breeze, and the island circulations.