Measurement Report: Spatial and vertical variability of aerosol optical properties during MOABAI mobile on-road campaign in North China Plain

Abstract

Abstract. The North China Plain (NCP) has been experiencing serious air quality problems since the rapid urbanization and industrialization and has been the subject of many studies over the years. This work presents mapping at a fine scale of the aerosol spatial and vertical variability obtained during the MOABAI campaign (Mobile Observation of Atmosphere By vehicle-borne Aerosol measurement Instruments) using a van equipped with a micro-pulse LIDAR, a sun photometer and in situ instruments, performing on-road measurements. The campaign was conducted from 5 May to 23 May 2017 and had as a main objective to map the pollutants distribution in Beijing and NCP area. A summary of aerosol properties during all measurement days and a comprehensive case study along the industrial Binhai New Area near Tianjin are presented. The highest AOD at 440 nm (1.34 and 1.9) were recorded during two heavy pollution episodes on 18 May and 19 May 2017, respectively. The lowest PBL (Planetary Boundary Layer) heights (< 1500 m) were recorded during the heavy pollution events, correlated with the highest AOD. Transport of dust from Gobi Desert was captured during the mobile measurements, impacting Beijing in the 9–13 May period. Exploring the NCP outside Beijing provided datasets in regions with lack of aerosol observation sites and allowed mapping higher aerosol concentrations when passing by polluted cities in NCP (Baoding, Tianjin and Tangshan). In this study, we provide the first mass concentration profiles derived from a mobile micro-pulse LIDAR, making use of complementary information on aerosol type from sun photometer and in situ data. The case study of 17 May 2017 revealed mean extinction coefficients of 0.14 ± 0.10 km−1 at 532 nm and total mass concentration of 80 ± 62 μg m−3 in the PBL (< 2000 m) for the mobile transect from Tianjin to Tangshan along the coast of Bohai Sea. The highest extinction (0.56 km−1) and mass concentrations (404 μg m−3) were found in the industrial Binhai New Area. The PM10 and PM2.5 fractions of the total mass concentration profiles were separated using the columnar size distribution derived from sun photometer measurements. A general good agreement was found between the lidar-derived PM concentrations at surface level and the ones recorded at the closest air quality stations along the transect, with the only exception along the industrial region near Tianjin port, where emissions were highly variable.

Enhancing Mobile Aerosol Monitoring with CE376 Dual-Wavelength Depolarization Lidar

“…In this manuscript, we describe extensively the methodology applied to retrieve aerosol optical properties from measurements of 180 the CE376 GPN lidar, named simply as CE376 hereafter. Detailed description on methods and corrections applied to the monowavelength CE370 lidar can be found in previous works (Pelon et al, 2008;Mortier et al, 2013;Popovici et al, 2018). For this study, two early versions of CE376 are used, one performing continuous observations at Lille, France and the other installed onboard a mobile platform during FIREX-AQ field campaign.…”

“…The CE370 lidar is an eye-safe micro-pulse lidar (Pelon et al, 2008;Mortier et al, 2013;Popovici et al, 2018) operating at 532 nm with 20 μJ pulse energy at 4.7 kHz repetition rate (table 1). It is designed with a shared transmitter-receiver telescope connected through a 10 m optical fiber to the control and acquisition system.…”

“…The backscattered signal is detected by photon counting with an 115 avalanche photodiode (APD). The CE370 lidar was designed by CIMEL Electronique to monitor aerosols and clouds properties up to 15-20 km with a vertical resolution of 15 m. For several field campaigns, the CE370 lidar embarked on mobile platforms has demonstrated the viability to characterize vertical aerosols properties in movement (Popovici et al, 2018(Popovici et al, , 2022. Therefore, the latest lidar model, CE376, operable up to two wavelengths is proposed to replace the CE370 lidar and continue the developments towards mobile aerosols monitoring (https://www.cimel.fr/solutions/ce376/, last access: 24 October 2023).…”

“…The AODph for the lidar wavelengths, 532 nm and 808 nm, are interpolated by following the Ångström law using AODph at 440 nm and EAEph(440/880). The main sources of uncertainties on the RCS profiles come from the overlap correction in the lower troposphere, and from the background irradiance in the higher atmosphere (Sassen and Dodd, 1982;Welton and Campbell, 2002;Guerrero-Rascado et al, 2010;Popovici et al, 2018;Sicard et al, 2020). For RCS at 532 nm from both CE376 systems used in this work, considerable underestimations on the incomplete overlap region (< 2.5 km) are observed for temperatures below 17 °C and above 35 °C, adding error into the lower range of the profiles.…”

“…The two mobile units called DMU-1 and DMU-2 (Dragon Mobile Unit), both equipped with photometer and lidar, performed onroad mobile measurements around major fires sources. The installation of the remote sensing instruments in the DMUs followed 500 the design of MAMS (Mobile Aerosol Monitoring System) platform (Popovici et al, 2018). DMU-2 was equipped with CE370 mono-wavelength lidar and PLASMA sun photometer, both tested and used in prior mobile campaigns (Popovici et al, 2018;Hu et al, 2019;Popovici et al, 2022).…”