Measurements And Study Of Atmospheric Aerosol Based On AML-3Lidar System

More than one year’s observation data about aerosol with AML-3Mie lidar System, combining with meteorological data, air pollution index (API) and trajectory model(HYSPLIT4.8) were used to study the distribution of the atmospheric aerosol characteristics, factors which affecting the distribution and origin of aerosol, diurnal variations of the height of the atmospheric boundary layer. The results show that:(1) In Spring morning, aerosol extinction coefficients are big in the low altitude and decrease rapidly with height, extinction decrease in afternoon, aerosol gather to the low-altitude and the structure is complex in evening. In summer, autumn or winter morning extinction coefficients decrease significantly with the height, while at14:00that are the biggest, and reduce in evening. Optical thickness takes on that spring<summer<autumn<winter, expectedly is0.28,0.36,0.49and0.62. Trend of extinction coefficients along different elevation angle is basically the same, difference between each direction is less in daytime than the night. Two-dimensional scanning can help to determine the atmospheric movement and evaluate air quality.(2) In sunny cloudless days extinction coefficients are very small and change little with height, while in haze days first increase and then reduce suddenly, in cloudy days increase and decrease rapidly. Denote optical thickness of0.3-lkm,1-2km,2-3km as AOD1, AOD2, AOD3. When the wind speed is0～4m/s, AOD1>AOD2>AOD3; when the wind speed is>4m/s, AOD2or AOD3is maximum; when the wind speed is>8m/s, extinction under2km is dominant. Track aerosol sources using HYSPLIT4.8model, and divide into dust, fuel-city, marine, dust-city four types. When the wind direction is North, North East, West, North West, optical thickness is0-0.25most probably; when the wind direction is South East, South and South West, optical thickness as0.25to0.5are more likely to occur; the wind direction is random when optical thickness is greater than0.5. Relative humidity and visibility are negatively correlated, the correlation coefficient is-0.53.(3)By using the gradient method and the meteorological sounding data to determine the boundary layer height from May8,2011to June7th. Daily boundary layer height experience four stages as "lift—shake up—steady—descend", each stage with different beginning and ending time, maintenance time, which related to other factors of that day.(4)A discussion of a heavy air pollution process in which aerosol extinctions varied to smaller and smaller:on February21st,2011, vertical aerosol extinction was strong, there were5obvious aerosol layer;22nd relative humidity decreased slightly, the aerosol extinction was weaker than21st but still high under lkm; on the third day, from ground to2km appeared some aerosol layers close to each other, aerosol began to uplift and transmit; on24th extinction coefficients under3km were all less than0.2km-1, and mixed vertically. Optical thickness decreased day by day, but the boundary layer height had uplifted from0.21km to1.8km constantly.(5)Particles’number concentration increased firstly (January to May) and then decreased (May to December). Daily distribution is unimodal. The particle concentration before12:00is relatively low, began to rise during the day, while around the peak at20:00. Registered the largest changes in October to December, January to March Second, April to June change relatively smooth. These characteristics associated with weather backgrounds and human activities. When wind direction to northeast aerosol number concentration is high. When wind speed<1.0m/s, the aerosol number concentration is typically40.0～80.0cm-3, and when wind speeds increased, particle concentrations rapidly decrease to below20cm-3.(6)During the gas-particle conversion process, the relative humidity was conducive to giant nuclear condensation to aerosol particles of accumulative mode; when relative humidity was small, particle number concentration and relative humidity showed a positive correlation, but if the relative humidity continues to increase to a certain extent, in this paper was74%, the negative correlation appeared.