Effects of aerosols on the atmospheric boundary layer temperature inversion over the Sichuan Basin, China

Abstract

The relationship between the aerosol and the boundary layer temperature inversion is analyzed based on the radiosonde, visibility, and PM2.5 mass concentration data from 2014 to 2016 in the wintertime over the Sichuan Basin. The radiosonde data are divided into four equal parts according to the previous 12-h average visibility and PM2.5 mass concentration. The mechanisms of the aerosol radiative effect on the boundary layer temperature inversion are further investigated by using the radiometer, the Mie scattering lidar, and the microwave radiometer in Chengdu. 1D-SBDART simulation is performed to better clarify the mechanisms. The occurrence probability of multi-layer temperature inversions is about 46.86% in winter over the Sichuan Basin. As the PM2.5 mass concentration increases (visibility decreases), the surface-based inversion frequency increases more consistently in the morning, while the elevated inversion increases more consistently in the evening. Aerosols can enhance the boundary layer temperature inversion at both daytime and nighttime due to the radiative effect, while clouds mitigate the enhancement by aerosol effects. The simulation results show that: from clean to heavy pollution conditions, in clear-sky the surface shortwave radiation reduces by 135.04 w·m−2 and the heating rate increases by 0.75 k·d−1; in cloudy sky the surface shortwave radiation reduces by 46.15 w·m−2 and the heating rate increases by 0.35 k·d−1. The case in Chengdu from 08:00 BJT on December 6 to 08:00 on December 10 in 2016 well illustrates the mechanisms.