Measurement report: Vehicle-based and In Situ Multi-lidar Observational Study on the Effect of Meteorological Elements on the Three-dimensional Distribution of Particles in the Western Guangdong–Hong Kong–Macao Greater Bay Area

Abstract. The distribution of meteorological elements has always been an important factor in determining the horizontal and vertical distribution of particles in the atmosphere. To study the effect of meteorological elements on the three-dimensional distribution structure of particles, mobile vehicle lidar observations, and in situ observations were presented in the western Guangdong–Hong Kong–Macao Greater Bay Area of China during September and October of 2019 and 2020. Vertical aerosol extinction coefficient, depolarization ratio, wind and temperature profiles were measured by using a micro pulse lidar, a Raman scattering lidar, and a Doppler wind profile lidar installed on a mobile monitoring vehicle. The mechanism of how wind and temperature in the boundary layer affects the horizontal and vertical distribution of particles was analyzed. The result showed that particles were mostly distributed in downstream areas on days with moderate wind speed in the boundary layer, while they presented homogeneously on days with weaker wind. There are three typical types of vertical distribution of particles in the western Guangdong–Hong Kong–Macao Greater Bay Area (GBA): surface single layer, elevated single layer, and double layer. Analysis of wind profiles and Hybrid Single-Particle Lagrangian Integrated Trajectory Model (HYSPLIT) backward trajectory revealed different sources of particles for the three types. Particles concentrated near the temperature inversion and multiple inversions could cause more than one peak in the extinction coefficient profile. There are two mechanisms that affected the distribution of particulate matter in the upper and lower boundary layers. Based on observational study, a general model of meteorological elements affecting the vertical distribution of urban particulate matter was made.