Application of Wind Profile Radar Data in Rare Heavy Haze Episode

Abstract

In this paper, the L-band wind profile radar data, densely-covered meteorological observation data and environmental monitoring data are used to analyze the characteristics and meteorological causes of a rare persistent heavy haze episode in Changsha from Jan. 27th to 29th, 2017. Results show that at 05:00 on the 28th, the air quality index (AQI) of Changsha exceeded 500, creating the historical record since 2012. During the heavy pollution episode, the south branch trough deepened continuously, and the strong southwest warm and humid air flow in front of the trough stably maintained for 4 days. Water vapor was continuously transported to Changsha, increasing the air humidity in this area, which was conducive to the maintenance and development of heavy pollution. In the maintenance stage of heavy pollution, the low-level jet nucleus, the weak upward motion and the weak vertical wind shear in the lower layer could limit the atmospheric vertical diffusion. The boundary layer height judged by the refractive index structure constant 2 is low, which is only about 300 m. Along with the strong inversion stratification in low levels, the vertical atmospheric turbulent exchange and thermal convection are weakened. With mountains on three sides and the Dongting Lake on the north, Changsha has a relatively weak environmental carrying capacity. Under adverse weather conditions, heavy pollution can be easily formed in Changsha, through the imported polluted air mass and local pollution accumulation. 1