Cloud-resolving simulation and mechanistic analysis of a squall line in East China

A severe squall line that occurred in east China on 12 July 2014 was simulated using the Weather Research and Forecasting model. Based on the cloud-resolving simulation results, the structural features and propagation mechanisms of the squall line were analyzed in detail. The main results were as follows: (1) The dynamic and thermodynamic structures of the simulated squall line were mainly characterized by a rain-induced cold pool in the near-ground level, front inflow in the low levels, descending rear inflow in the middle levels, and slightly ascending front-to-rear outflow in the upper levels. (2) The coupling between the low-level updrafts induced by the cold pool and the upper-level updrafts caused by the gravity wave was the main reason for the development and propagation of the squall line. (3) The descending mid-level rear inflow cut off the front inflow in the low levels and eventually resulted in the squall line's decay. Based on these findings, a conceptual model of the initial, mature and dissipating stages of the squall line is presented.