资源环境科技发展态势分析平台

Simulations using a convection-permitting numerical model (The Weather Research and Forecasting, WRF) are conducted to investigate the mechanisms responsible for the maintenance and organization of long-lived moist convection into a Mei-yu rainband (091800-101,800 UTC June 2008). This rainband was composed of multiple two-dimensional precipitation bandings, being elongated from the southwest to the northeast with the narrow width.

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.