A028-05
Impact of Aerosol-Cloud Interaction on Boundary Layer Structure and Surface Pollution: A Case Study in Eastern China

Monday, 7 December 2020: 20:46
Virtual
Changrui Xiong, Peking University, Beijing, China, Jing Li, Peking University, Department of Atmospheric and Oceanic Sciences, Beijing, China, Yucong Miao, Chinese Academy of Meteorological Sciences, Beijing, China and Zhenxin Liu, IAP Insititute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
Recorded Presentation
Abstract:
Aerosols affect the Earth’s radiative balance through both direct effect and the interaction with hydrological cycle. In this study, we use the online-coupled Weather Research and Forecasting model with Chemistry (WRF-Chem) to simulate the direct, semi-direct and indirect impacts of aerosols over Shanghai during November 19th, 2016, in order to quantify aerosol’s impact on the boundary layer structure and surface pollution in cloudy condition. It is noted that in this case when direct and semi-direct effect coexists, it is necessary to examine their individual contribution. To isolate the two effects, we design intermediate experiments in which air pollution was simulated in the model while cloud was imported from the simulation with or without anthropogenic aerosols feedback.

Results show that semi-direct effect reduces cloud water path before 14:00LT due to heating of the cloud by absorbing aerosols, whereas indirect effect increases cloud droplet concentration and cloud water path throughout daytime due to the increase of CCNs and suppression of rainfall. More specifically, from 07:00LT to 18:00 LT, indirect effect has the largest impact on PBL, which reduces net shortwave flux at surface, 2m air temperature, and PBLH by a maximum of 215.8Wm-2, 2.2°C, 255.7m, respectively, resulting in the increase of PM2.5 concentration by a maximum of 27.9 ug m-3 in the regional average of Shanghai. The second largest impact is caused by direct effect, which reduces net shortwave flux at surface, 2m air temperature, and PBLH by a maximum of 34.5Wm-2, 0.27°C, 53.4m, respectively, resulting in the increase of PM2.5 concentration by a maximum of 7.1 ug m-3. The least impact is caused by semi-direct effect, which increases shortwave flux at surface, 2m air temperature, and PBLH by a maximum of 3.4Wm-2, 0.06°C, 29m, respectively, resulting in the decrease of PM2.5 concentration by a maximum of 1.2 ug m-3. Further, we examine the radiative effect of BC and find that it has the largest impact on direct effect per unit mass, accounting for ~50% of the effect with only ~5% of the total mass of aerosols. We also find that BC dominates the semi-direct effect as well, for the decrease of cloud water caused by BC is larger than that caused by total radiative effect of all aerosols.

<< Previous Abstract | Next Abstract >>