LIU Sihan ¹ , WANG Honglei ¹ , ZHAO Delong ² , GAO Ying³ , ZHAO Tianliang ¹ ,PEI Yuxuan ¹ , KE Yue ¹ , WU Zihao

(1. Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration,and Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD) , Nanjing University of Information Science & Technology, Nanjing 210044; 

2. Beijing Weather Modification Office, Beijing 100089,China;

3. Unit 66137 of PLA, Beijing 100010, China)

Abstract:From August 1 to 5, 2018, combined PM2. 5 and O3 pollution occurred in the Beijing-Tianjin-Hebei region. In this study, we took advantage of the King Air aircraft equipped with passive cavity aerosol probe ( PCASP) , single particle soot photometer ( SP2) and AIMMS-20 probe to determine 110- 600 nm aerosol number concentrations, 36- 526 nm black carbon aerosol ( BC) mass and number concentrations, as well as meteorological factor data in Beijing and Baoding on August 5. Then, the particle size distribution of aerosols, BC in vertical and horizontal directions were analyzed, in addition to that the radiative forcing and atmospheric heating rate caused by BC were calculated. The results show that the aerosol number concentration over Beijing first in creased atarate of 144-1 041 cm - 3 / 100 m, then remained unchanged and thereafter decreased at a rate of 632-891cm3/100m with the altitude. Incomparison, the aerosol number concentration over Baoding decreased with the altitude at a rate of 270 cm - 3 / 100 m. In the case of the BC number concentration, the values over Beijing and Baoding were first constant and then decreased with the altitude at a rate of 9- 28cm - 3 / 100 m. The temperature inversion layer at about 2 000 m has resulted in a decreased rate of aerosol number concentration of 170-336 cm - 3 / 100 m. The number concentration spectrum of aerosol at different altitudes were bimodal with peak particle sizes at 140 nm and 240-280 nm. The BC number concentration spectra at different altitudes was unimodal with a peak particle size at 76-91 nm. At 09 05 and 11 30, the number and mass concentrations of BC in Beijing were concentrated below 500 m altitude, which were respectively influenced by the downward vertical wind from 0-500 m and horizontal wind shear from 500-750 m altitude. The extent of BC aging increases with altitude below the 500 m and varied little above the 500 m altitude. The heating effect of BC was observed mostly below the 500 m altitude with a heating rate of about 0. 62 K / d. In comparison, the heating rate of BC above 500 m altitude was around 0. 06-0. 25 K / d. During level flight, the aerosol number concentration spectrum in the high aerosol, but low BC region was bimodal with a peak particle size of 140 nm and 280 nm, and the other three regions were unimodal with a peak particle size of 140 nm. The BC number concentration spectra of all four regions were unimodal with a peak particle size of 69- 91 nm. The concentration of BC and aerosol number influenced the aging degree of BC. Under a constant aerosol number concentration, it has been found that the higher the BC number concentration was, the smaller the BC aging degree was and vice versa.