| In this paper, haze aerosols physical characteristics in Shanghai which was one of the most severely haze-affected areas in China were analyzed. First, the meteorological data and aerosol ground observation from Shanghai Meteorological Bureau were used to analyze climatic characteristics and meteorological cause of haze as well as physical characteristics of aerosols during haze periods. Then the height of boundary layer was retrieved and its variation for different intensity haze was analyzed using data from ground-Micro Pulse Lidar. The vertical distributions of aerosols in haze at Yangtze River Delta region were presented based on. the advanced CALIPSO satellite observations.The result showed that the multiyear average number of haze days per year was about 154.6 in Shanghai. Annual variation of haze was evident. November, December and January showed high occurrence of haze. Haze occurred most frequently in spring and winter, mild haze in spring and severe haze in winter. Wind direction, wind speed, precipitation and number of precipitation days all had an affinity with the occurrence of haze. When westerly, southwest or northwest winds blowed in Shanghai, there was higher occurrence of haze, while north, northeast east or south-east wind could purify atmosphere leading to less haze. Thickness and intensity of inversion layer influenced on haze. From mild haze to moderate one and then to severe haze, thickness of inversion layer from surface increased gradually while the height decreased and intensity increased gradually. During haze periods, there were more fine particles in the atmosphere and aerosol mass concentration, volume concentration, black carbon concentration and aerosol scattering coefficient were higher than those during non-haze periods. The highest concentration of black carbon and proportion of fine particles occurred in winter while the largest measurement of mass concentration and coarse particles of aerosols were in spring.Among the derivative-based method, normalized oblique derivative method and wavelet covariance transform method, the third can obtain the best result of boundary layer height retrieval. Under the same weather conditions and aerosol content, visibility and boundary layer height had a consistent variation trend. But the highest boundary layer height appeared earlier than the maximum visibility. The maximum boundary layer height appeared in summer, followed by the fall and the lowest was in spring and winter. When severe haze appeared, the boundary layer height was less than 650m, while the corresponding height was between 550-850m during moderate haze, 550-1100m during light haze and 850-1200m during non-haze periods.Observations from CALIPSO data were consistent with that of ground-based. In the Yangtze River Delta region, when haze occurred, aerosols were mostly concentrated below 2km altitude. Within such a height, back scattering coefficient mainly ranged from 0.001 to 0.003km-1·sr-1, depolarization ratio ranged from 0 to 20% and color ratio ranged from 0.2 to 0.9. Based on the statistics for spring, autumn and winter, attenuated back scattering in spring was smallest, depolarization ratio and color ratio in spring were largest. Due to dust transport from north in spring, there were relatively large particles with irregular shape during haze periods, in autumn, aerosol particles were smaller and more regular than the other two seasons. When haze occurred, the lower the altitude was, the larger and more irregular the particles were.
|
PDF Full Text Request