Comment on egusphere-2023-252

Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> Black carbon (BC) exerts potential effect on climate, especially in the Tibetan Plateau (TP), where the cryosphere and environment are very sensitive to climate change. The TP saw the record-breaking aerosol pollution event during the period from April 20 to May 10, 2016. This paper investigated the meteorological causes, trans-boundary transport flux of BC, and aerosol-meteorology feedback as well as its effect on trans-boundary transport flux of BC during this severe aerosol pollution event via using observational and reanalysis dataset and simulation from the coupled meteorology and aerosol/chemistry model (WRF-Chem). By analyzing the weather maps derived from reanalysis dataset, it is found that the plateau vortex and southerly winds were key factors that contributed to the severe aerosol pollution event. Subsequently, with the good performance of WRF-Chem model on the spatiotemporal characteristics of meteorological conditions and aerosols, the trans-boundary transport flux of BC during the pollution event was investigated. The results show that the vertically integrated cross-Himalayan transport flux of BC decreases from west to east, with the largest transport flux of 20.8 mg m^&minus;2 s^&minus;1 occurring at the deepest mountain valley in southwestern TP. Results from simulations with and without aerosol-meteorology feedback show that aerosols induce significant changes in meteorological conditions in the southern TP and Indo-Gangetic Plain (IGP), with the atmospheric stratification being more stable and the planetary boundary layer height decreasing in both regions, and 10-m wind speed increasing in the southern TP but decreasing in the IGP. Changes in meteorological conditions in turn lead to a decrease of surface BC concentration with value up to 0.16 &mu;g/m³ (50 %) in the southern TP and an increase of surface BC concentration with value up to 2.2 &mu;g/m³ (75 %) in the IGP. By excavating the impact of aerosol-meteorology feedback on the trans-boundary transport flux of BC, it has been acquired that the aerosol-meteorology feedback decreases the integrated transport flux of BC from central and western Himalayas towards the TP. This study not only provides crucial policy implications for mitigating glacier melt caused by aerosols over the TP, but also is of great significance to the ecological environment protection for the TP.