Observational understanding of aerosol-cloud interaction based on in-situ aircraft measurements in northern China

Observational understanding of aerosol-cloud interaction based on in-situ aircraft measurements in northern China

Chuanfeng Zhao

Beijing Normal University

Abstract: This study provides observational understanding about the aerosol-cloud interaction in North China plain based on in-situ aircraft observations. First, a statistical analysis of cloud properties is carried out for both clean and polluted conditions using 27 clouds obtained from 7 flights in September, 2015. It shows that the droplet size distribution is narrower with more droplets at smaller size bins under polluted than under clean conditions, implying that aerosols decrease cloud droplet effective radius during the study period. Further analysis about the vertical profiles of cloud droplet effective radius (re) and cloud liquid water content (LWC) also indicates this point. While cloud LWC is larger under polluted than clean conditions, the cloud re under polluted condition is still smaller than that under clean condition. Quantitatively, the inverse value regarding the relative changes of cloud droplet re with aerosol number concentration, which is defined as the aerosol first indirect effect, is around 0.1-0.19.

Two case studies have also been investigated for one stratus cloud and one shallow cumulus cloud, respectively. The stratus cloud case study shows that the aerosol-cloud interaction is most clear for low clouds within planetary boundary layer. The shallow cumulus cloud case study shows more findings: the aerosol-cloud interaction depends on the vertical velocity, aerosol concentration, and water supply. Potential mechanisms how the these influential factors affect the aerosol-cloud interaction have been discussed.

References:

Yang Yang, Chuanfeng Zhao, Xiaobo Dong, Genchang Fan, Yuquan Zhou, Yang Wang, Lijun Zhao, Feng Lv, Fei Yan (2019), Toward understanding the process-level impacts of aerosols on microphysical properties of shallow cumulus cloud using aircraft observations, Atmospheric Research, 221, 27-33.

Zhao, Chuanfeng, Lijun Zhao, and Xiaobo Dong (2019), A case study of stratus cloud properties using in situ aircraft observations over Huanghua, China, Atmosphere, 10, 19.

Zhao, Chuanfeng, Yanmei Qiu, Xiaobo Dong, Zhiene Wang, Yiran Peng, Baodong Li, Zhihui Wu, and Yang Wang (2018), Negative Aerosol-Cloud re Relationship from Aircraft Observations over Hebei, China. Earth and Space Science, 5, 19-29.