The covariability between temperature inversions and aerosol vertical distribution over China

Abstract

Temperature inversions (TI) have a unique impact on the regulation of aerosol distribution. However, it remains unclear the covariability of TI and aerosol vertical distribution. To address this issue, ten years CALIPSO observations and the fifth-generation European Centre for Medium-Range Weather Forecasts atmospheric reanalysis system (ERA5) data from January 2008 to December 2017 across China were collected. The aim was to explore the relationship between TI and the aerosol vertical distribution. The characteristics of TI and aerosol vertical distribution have been analysed in the Taklimakan Desert (TD), North China (NC), South China (SC) and Sichuan Basin (SB). The results demonstrate that the frequency of TI, inversion strength (ΔT), and TI height (TIH) follow a similar seasonal pattern across the four areas. Specifically, they are highest in winter, followed by spring and autumn, and the least in summer. Notably, NC exhibits a significantly higher average frequency (10.3%) of TI during summertime compared to the other regions. This may be a result of the heating effect of the elevated black carbon aerosol on the upper atmosphere. Moreover, the observations demonstrate that aerosol optical depth (AOD) above the TIH in the four areas is greater during spring and summer months compared to autumn and winter. It indicates that there is an obvious aerosol high-level transport over the Chinese mainland in spring and summer. In winter months, most of the aerosols are located below the TIH. This phenomenon occurs due to the influence of a strong inversion layer and adverse atmospheric ventilation conditions. In addition, the average AOD below TIH increases with the ΔT increased in TD region, supporting the hypothesis that a strong inversion can suppress surface aerosols below the TI. Conversely, in NC and SC regions, the average AOD below (above) TIH decreases (increases) as the ΔT increases. It indicates that the strong atmospheric stability forms a more effective transmission channel, resulting in the accumulation of aerosols above TIH. These findings have important support for studying aerosol transport.