Abnormally Shallow Boundary Layer Associated With Severe Air Pollution During the COVID-19 Lockdown in China

Tianning Su; Zhanqing Li; Youtong Zheng; Qingzu Luan; Jianping Guo

doi:10.1029/2020GL090041

Abnormally Shallow Boundary Layer Associated With Severe Air Pollution During the COVID-19 Lockdown in China

Geophys Res Lett. 2020 Oct 28;47(20):e2020GL090041. doi: 10.1029/2020GL090041. Epub 2020 Oct 19.

Authors

Tianning Su¹, Zhanqing Li¹, Youtong Zheng¹, Qingzu Luan^{1

2}, Jianping Guo³

Affiliations

¹ Department of Atmospheric and Oceanic Sciences and ESSIC University of Maryland College Park MD USA.
² Beijing Municipal Climate Center Beijing China.
³ State Key Laboratory of Severe Weather Chinese Academy of Meteorological, Sciences Beijing China.

Abstract

After the 2020 Lunar New Year, the Chinese government implemented a strict nationwide lockdown to inhibit the spread of the Coronavirus Disease 2019 (COVID-19). Despite the abrupt decreases in gaseous emissions caused by record-low anthropogenic activities, severe haze pollution occurred in northern China during the COVID lockdown. This paradox has attracted the attention of both the public and the scientific community. By analyzing comprehensive measurements of air pollutants, planetary boundary layer (PBL) height, and surface meteorology, we show that the severe air pollution episode over northern China coincided with the abnormally low PBL height, which had reduced by 45%, triggering strong aerosol-PBL interactions. After dynamical processes initiated the temperature inversion, the Beijing metropolitan area experienced a period with continuously shallow PBLs during the lockdown. This unprecedented event provided an experiment showcasing the role of meteorology, in particular aerosol-PBL interactions in affecting air quality.

Keywords: COVID‐19; aerosol; air pollution; boundary layer.