Measurements Of Different Haze Periods In Hangzhou Urban By Lidar Satellite

With the economic development and urbanization process, The growing of low visibility weather has become one of the most important environmental problems that majority domestic cities faced with currently. And haze is now a kind of pollution rather than a type of weather phenomena. The PM2.5data in Hangzhou monitored and released since March25,2012, indicating a severe air pollution situation calls for control and treatment urgently. Haze observation is now dependent on surface stations and optical remote sensing, which mainly provide air quality and haze range imformation but little about vertical distribution of aerosols. The Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite was launched in April2006by National Aeronautics and Space Administration (NASA) and French Centre National d’Etudes Spatiales (CNES).CALIPSO provides global cloud and aerosol profiles with high vertical resolution and accurate depolarization measurements, makes it an effective means of monitoring the vertical distribution characteristics of atmospheric aerosol during haze periods.In this study, data from7surface meteorological stations and environmental monitoring station used to identify the historical evolvement, seasonal change and monthly variation process of haze in Hangzhou, according to the Observation and Forecasting Levels of Haze (QX/T113-2010). Vertical distribution characteristics during haze and haze-free periods in downtown were analyzed to find out a method to distinguish haze based on CALIPSO. The main contents are as follows:(1) Temporal evolution of haze in Hangzhou:There are three periods in the temporal evolution of annual haze days during1951-2010in Hangzhou:The recovery period of environment from1951to1964, the stabilization period from1965to1975, and the rapidly increase period after1975. The seasonal variation characteristic of Hangzhou, which is mainly affected by the climate conditions, is:Winter>Spring&Autumn>Summer. The monthly changing characteristics are:haze appears most frequently in December and January, and least frequently in July.(2)Vertical distribution of atmosphere in Hangzhou downtown:Alone with the ascending of height, the attenuated backscatter coefficient (BKS), volume depolarization ratio (VDR) and total attenuated color ratio (COR) is decrescent, proportion of spherical aerosols increases. The frequencies also reduce when the values of these parameters increasing. Atmospheric scattering ability in0-2km is stronger than other altitude range, the peak value of532nmBKS is the range of0.0008-0.0025km-·sr-1, and VDR and COR concentrate in the range of0-15%and peak frequency change from0.4to1.0.Hygroscopicity particles drop down when absorbed moisture, weakening the scattering intensity in the planetary boundary layer (PBL), remaining medium-sized spherical particles. On the other hand, scattering intensity enhances in the medium troposphere, and the atmospheric structure remains almost the same during dry and damp haze priode in the high troposphere. Compareing the different degree of haze, spherical fine aerosols is the main constituent during mild haze period, and it become the spherical coarse aerosols and non-spherical fine aerosols during moderate and severe haze period respectively.(3) Haze period distinguish in Hagnzhou downtown based on CALIOP:According to the F-test statistic results of the three parameters and the atmospheric vertical distribution characteristics of different weather process, parameters at the height range of0.5-1.2km can be used to distinguish different degree of haze. SPSS discriminant operation results show that combination of VDR/BKS/COR at each height level can distinguish haze and haze-free period effectively. With the vertical visibility calculated with corrected extinction coefficient, the thickness of haze layer is obtained, which is conducive to the scientific understand of aerosol distribution during different haze periods.(4) Analysis of haze source in Hangzhou on January2013:The haze period on January26,2013is analyzed with the ground meteorological data, main atmospheric pollutants concentration and CALIOP data. The result shows that thickness of haze layer is about1km the same day, the pollutants mainly concentrated in the surface in the influence of meteorological condition, such as static wind, inversion layer and no-precipitation process. Accumulation of local pollutant, such as vehicle exhaust, also provides favorable conditions for haze. Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model inversion result illustrate the pollutants from circumstance also contribute to the formation of haze. Based on all these above, the control and treatment of haze pollution need the combination of local and regional governance.