The Mechanism Of The Temporal And Spatial Variation Of The MABL Over The Yellow And East China Sea

In this paper, the obtained Global Positioning System (GPS) sounding data are used, combined with Climate Forecast System Reanalysis (CFSR) reanalysis data, satellite data, Qingdao, Taizhou L-band radar data and WRF model, to analyze the spatial and temporal variation of the marine atmosphere boundary layer (MABL) on Yellow and East China Sea. The paper focused on the mechanism of the variation, and obtained the following conclusions:GPS sounding data show that the sea-air temperature difference (SAT) determines the type of MABL, positive temperature difference correspond with convective boundary layers, negative to stable boundary layers. Compared to the terrestrial boundary layer, the diurnal variation of MABL is small. The MABL in May is very low, the SAT and MABL height are highly correlated in the warm zone, and in the cold zone wind shear is more significant. Solar radiation can have extent effect on the MABL height. In November, the MABL is much higher than in May, the SAT, solar radiation can affect the height of the MABL, wind shear contributes little. Nov observations indicate that the variation of the synoptic system also have a significant effect on MABL.The CFSR data showed that MABL is the lowest in summer and highest in winter, and determines the height of the humid layer above the sea. Meanwhile, with the background circulation, on the warm flank of the Kuroshio front, the water vapor can break MABL and reach to the troposphere in May. Vapor in Nov is substantially limited to the MABL.The L-band radar soundings of Qingdao and Hongjia station, shows that the atmospheric boundary layer of the coastal areas has the same seasonal changes with MABL, they are able to represent the state of the Yellow-East China Sea MABL characteristics. But there are more dramatic changes in diurnal variation, so further researches on the MABL and its impact factors on coastal L-band sounding data have limitations.Background wind on the East China Sea Kuroshio front (ESKF) is possible to make impact on MABL through low-level wind field curl and divergence changes. In March, pressure adjustment mechanism on the ESKF with northeasterly background winds would format strong positive curl center on the ESKF warm flank. This center generates Ekman pumping and enhances the upward motion, elevates the MABL. It is the reason of the significantly increasing local precipitation. April, on the contrary, has a weaker curl center than March. It is because of the weak background winds and indeterminate wind directions.