A study on triggering and maintenance mechanism of a linear quasi-stationary convection system in South China

At about 08:00 on May 10, 2014, there were scattered convection cells evolving in the vicinity of Yangjiang, Guangdong Province of China. They merged into a quasi-linear-stationary meso-scale convective system (MCS) with the scale of about 200 km. This MCS lasted for almost 16 hours with a maximum rainfall of 372 mm. By analyzing observational data and conducting a terrain sensitive numerical simulation experiment, it is found that under a favorable large-scale water vapor thermal condition, the special meso-scale dynamic structure of continued interaction of the thermal structure with the Yunwu Mountain terrain is the key factor in the MCS triggering and maintenance mechanism. The night-enhanced super-low level jet (SLLJ) constitutes a"channel"for the warm and humid air flowing to the north, enhancing the unstable convective stratification, so that the warm and humid air was blocked by the mountain terrain and forced up to reach the free convection height, and the Convective Available Potential Energy (CAPE) of the air is triggered to release. Then dispersed convective cells emerged near the Yunwu Mountain, and moved eastward under the middle level leading wind. Due to the above-mentioned meso-scale dynamic thermal structural features with the topographical elevation of the Yunwu Mountain continuously existed, the linear quasi-stationary MCS formed and maintained for a long time.