The Development And Structure of an Oceanic Squall Line Systems During the South China Sea Summer Monsoon Experiment

The South China Sea Monsoon Experiment (SCSMEX) was conducted in South China Sea (SCS) and surrounding areas during MayæJune 1998. The primary goal of the experiment is to provide a better understanding of the key physical processes for the onset, maintenance and variability of the monsoon over the Southeast Asia and southern China leading to improved monsoon predictions. As the first comprehensive field experiment aiming on the SCS summer monsoon, the goals of the mesoscale program associated with the primary objective are: 1) to define the initiation, structure, evolution and dynamics of precipitation processes associated with the onset and mature phase of the SCS monsoon, and 2) to obtain quantitative rainfall estimates, vertical air motion and inferences on microphysical structure over a tropical oceanic site. Over 3-h Dual doppler radar analysis was performed to study the development and structure of an oceanic squall line system occurring on 24 May after the onset of SCS summer monsoon onset. Many interesting characteristics of the mesoscale convection in this region were found. Comparing with the classical mesoscale convective system structure well documented in the literature, the special features of this squall line system include: 1) with maximum reflectivity as high as 60 dBZ, this strong convective system has very small region of stratiform rain; 2) the small stratiform region is leading instead of trailing to the main convective counterpart; 3) rather than a narrow ribbon of vertical velocity maximum near the leading edge, this system has a longish vertical velocity maximum across the system, and 4) the center of the maximum vertical velocity is at a relatively high level.