Observational Study On The Characteristics Of Aerosol And The Retrieval Of Vertical Distribution Over Semi-Arid Region

The climatic effect of aerosol is one of the hottest issues in the researches of global climate change. The aerosol concentration, size distribution, scattering coefficient and absorption coefficient are the main parameters of aerosol physical and optical characteristics, and in researches of climatic effects of aerosol as well.Using the continuous data measured with APS-3321,AE-31 from November 1st, 2007 to October 31st,2008 and M9003 from Aug 1st 2007 to 31st 2008 at Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL), the physical (concentration, size distribution) and optical (scattering coefficient, absorption coefficient) characteristics of aerosol were analyzed. Based on the empirical model of the concentration and extinction coefficient of aerosols obtained on ground surface, the vertical profile of aerosol extinction coefficients retrieved from the data measured by Micro Pulse Lidar (MPL-4), a method of estimation for the vertical distribution of aerosol is developed. The main conclusions are as follows:1. The annual mean number concentration of aerosol over this region is 191/cm3, the mass concentration is 0.107 mg/m3. The peak of both type of concentrations appeared in December. The number concentration reaches the valley point in June,mass in sepember. The diurnal variation of both type of concentrations is single-peak type with the maximum appeared around 11:00BST and the minimum at about 18:00 BST.2. The size distribution of number concentration is unimodal type and most of particles are centralized at 0.673μm or so. The size distribution of mass concentration has double-peaks and the first peak is near 0.777μm, the second is near 5.048μm.3. The annual mean scattering coefficient of aerosol over this region is 158.86 Mm-1, absorption coefficient is 14.11 Mm-1. Mass scattering coefficient is 1.22m2/g, mass absorption coefficient is 0.13m2/g. The scattering coefficient and the absorption coefficient are single-peak type in annual variation. The peak of both type of concentrations appear in winter season. The diurnal variation of both type of coefficients is single-peak type.4. The results retrieved by Micro Pulse Lidar show that, the vertical distribution of aerosol concentration over this region it is greater at high altitude than that near ground surface in the clear-cloudless days. The maximum area is about 350 meters in height from the surface around 6:00-10:00 BST. The vertical distribution of aerosol is in good agreement with the vertical distributions of air temperature and water vapour.5. A empirical model of aerosol suitable for simulating the variation of aerosols in this region is developed.