Characterization of the vertical evolution of urban nocturnal boundary layer by UAV measurements: Insights into relations to cloud radiative effect

Lin Shen; Jiaoshi Zhang; Yin Cheng; Xiaofeng Lu; Haosheng Dai; Dexia Wu; Da-Ren Chen; Jianguo Liu; Huaqiao Gui

doi:10.1016/j.envres.2023.116323

Characterization of the vertical evolution of urban nocturnal boundary layer by UAV measurements: Insights into relations to cloud radiative effect

Environ Res. 2023 Sep 1:232:116323. doi: 10.1016/j.envres.2023.116323. Epub 2023 Jun 2.

Authors

Lin Shen¹, Jiaoshi Zhang², Yin Cheng¹, Xiaofeng Lu¹, Haosheng Dai¹, Dexia Wu³, Da-Ren Chen⁴, Jianguo Liu⁵, Huaqiao Gui⁶

Affiliations

¹ Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, 230031, China; University of Science and Technology of China, Hefei, 230031, China.
² Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, 230031, China. Electronic address: jszhang@aiofm.ac.cn.
³ Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, 230031, China.
⁴ Particle Laboratory, Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, VA, 23284, USA.
⁵ Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, 230031, China; University of Science and Technology of China, Hefei, 230031, China; CAS Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China.
⁶ Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, 230031, China; CAS Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China. Electronic address: hqgui@aiofm.ac.cn.

PMID: 37271438
DOI: 10.1016/j.envres.2023.116323

Abstract

The complex structure of the nocturnal boundary layer (NBL) and its impact on air pollution remain poorly understood. In this study, we present in-situ nocturnal flight measurements onboard an unmanned aerial vehicle (UAV) during the wintertime of 2022 at an urban site in Hefei, China. Besides, co-located measurements of radiation intensity and total amount of cloud were conducted. The vertical distribution of temperature, particle number concentration, and relative humidity were obtained to study the structure of NBL and the key factors driving the evolution of the NBL. A multi-layer inversion boundary layer was observed during haze and fog episodes, which affects the vertical diffusion of particles near the surface and leads to a vertical gradient of particle number concentrations. The particle size distribution demonstrates a drastic vertical variation over different sections of the nocturnal boundary layer: homogeneously mixed in the SBL and the RL layer, sharply reduced in the IL. It is found that the temperature and particle number concentration differences between near-surface and at 500 m are highly related to variations of the radiation intensity and the amount of cloud. The decreased cloud cover enhances the surface cooling, creating a shallow NBL with multiple inversion layers, which reinforces the suppression of vertical diffusions and consequently promotes the accumulation of aerosols within the NBL. This reveals an important mechanism for the impact of NBL evolution modulated by cloud radiative effect on the formation of urban haze.

Keywords: Cloud and radiation effect; Multi-layer inversion boundary layer structure; Nocturnal boundary layer; Unmanned aerial vehicle.

MeSH terms

Air Pollutants* / analysis
Air Pollution* / analysis
Environmental Monitoring
Particulate Matter / analysis
Unmanned Aerial Devices

Substances

Air Pollutants
Particulate Matter