Relative roles of dry intrusion, latent heat and instabilities in the Mei-yu rainband life cycle: A case study

In addition to establishment of the Mei-yu frontal zone, the northwesterly flow behind the mid-tropospheric trough also brought about upper-level dry air. The downward transport of the dry air had a high value of potential vorticity and just overrode the low-level moist southwesterly component, inducing the conditional instability (CI) and frontogenesis at the coherent regions. This behavior combined with the Mei-yu frontogenesis, leading to successive convection to maintain the rainband, whereas the latent heat was not directly linked to the rainband longevity. The releases of CI, conditionally symmetric and inertial instabilities were simultaneously present in the bandings, as an indication of the mechanisms for the formation of banded structures. Therefore, the mesoscale circulations in banded convection developed in the form of coexisted upward and slantwise motions. Our attempt to integrate the dry intrusion and multiple instabilities could be a vital significance in discussing the Mei-yu rainband development.