Numerical simulation study for the structure and evolution of tropical squall line

The occurrence and evolution of an oceanic tropical squall line observed on 22 February 1993 during TOGA-COARE over the equatorial Pacific Ocean were simulated by use of a three-dimensional, nonhydrostatic storm-scale numeric al model ARPS. The capacity of ARPS to simulate such tropical squall line w as verified. The structure and dynamic mechanism of the squall line were di scussed in details as well The impacts of the different microphysical proce ss that including the ice phase and warm rain schemes on structure and evol ution of the squall line were investigated by the sensitive experiment. The simulations of the three-dimensional structure and evolution of the squ all line are closely related with the observations when the proper microphy sical processes were employed. The more latent heating released in the ice phase processes associated with the freezing process leads to strengthening deep convection due to the vertical gradient of buoyancy, which results in a long life of the convective system. In contrast, the warm rain process i s characterized by short life period, more pronounced rearward tilt structu re and extension of stratiform cloud.