[Change and analysis of background concentration of air pollutants in north China during 2008 Olympic Games].

To understand the atmospheric background in North China and evaluate the effect of pollutant emission control as well as the influence of contaminant transportation in the regional pollution, during the 2008 Olympic Games, concentrations of four main air pollutants were observed from June to November at Xinglong station which is the regional background station of North China. We compared the concentrations and diurnal variations in different periods, analyzed the pollution transportation using the ground meteorological data and the backward trajectory model and compared the concentrations between different observation stations in Northern China. The results indicated that the concentrations of NOx, SO2, O3 and PM2.5 in summer were 8.4, 10.5, 126.0 and 59.8 microg x m(-3) respectively and in autumn were 11.7, 17.2, 97.5 and 30.7 microg x m(-3) respectively. During the period of Olympic (2008-08-08-2008-08-24), the concentrations of NOx, SO2, O3 and PM2.5 were 6.6, 6.8, 100.5 and 33.3 microg x m(-3) and reduced 29.0%, 46.9%, 18.6% and 36.5% respectively compared to the average concentrations of the period before and after Olympic Games. The concentration of NOx has reduced 62.5% and the PM2.5 has reduced 29.0% compared to the same term of Olympic in 2007. The air quality has obvious improvement in North China during the Olympic Games. Before the emission control, the concentrations of pollutants were lower in the night and became higher gradually in the daytime and reached the peak values in 17:00-20:00 which can indicate the accumulation of regional pollution transportation in Xinlong. In the emission control period, the accumulation of pollutants in afternoon was obviously weakened and the transportation of pollutants was lower which can reveal the obvious effect of the emission control in Beijing and peripheral areas. The atmosphere in Xinglong was mainly influenced by the monsoon from south direction in summer and autumn and the pollution of Xinglong was seriously influenced by the regional pollution in the south direction. Compared the concentrations between different stations, we can conclude that in summer and autumn the pollutions of NOx and SO2 are relatively lower, the pollution of O3 is not allowed to be optimism and the pollution of PM2.5 is very serious which should be paid enough attentions to.

[Analysis on concentration variety characteristics of atmospheric ozone under the boundary layer in Beijing].

Based on the atmospheric ozone sounding data, the average monthly and seasonal variety principles of atmospheric ozone concentration during six years are analyzed under the boundary layer in Beijing. The results show that the monthly variation of atmospheric ozone are obvious that the minimum values appear in January from less than 10 x 10(-9) on ground to less than 50 x 10(-9) on upper layer (2 km), but the maximum values appear in June from 85 x 10(-9) on ground to more than 90 x 10(-9) on upper layer. The seasonal variation is also clear that the least atmospheric ozone concentration is in winter and the most is in summer, but variety from ground to upper layer is largest in winter and least in summer. According to the type of outline, the outline of ozone concentration is composite of three types which are winter type, summer type and spring-autumn type. The monthly ozone concentration in different heights is quite different. After analyzing the relationship between ozone concentration and meteorological factors, such as temperature and humidity, we find ozone concentration on ground is linear with temperature and the correlation coefficient is more than 85 percent.

[Introduction and calibration of the Chinese sun hazemeter network].

Much of the current uncertainty in the quantitative assessment of the climate and environment change is due to our lack of knowledge of the aerosol, for which the large-scale sun hazemeter ground-based network directly provides basic data. The data also can revise the results of the satellite remote sensing. Depending on the stations of CERN, the standard network was first built in China. The accurate and reliable hazemeter (LEDs) was uniformly used in the network. The hazemeters were calibrated by Langley plot method and transfer calibration and were uniformly checked. The AODs, which were synchronously retrieved from hazemeters (RSD < 3%) and CEMIL (RSD < 5%), were coherent and comparable. The stability and reliability of the hazemeters and the network was approved.

[AOD and angstrom parameters of aerosols observed by the Chinese sun hazemeter network from August to December 2004].

Atmospheric aerosol optical depth (AOD(lamda=500 nm)), Angstrom turbidity coefficient (beta) and Angstrom wavelength exponent (alpha) are obtained using the CERN sun hazemeter network from Aug to Dec, 2004. The results are as follows: At the Tibetan Plateau, Haibei and Lhasa, the mean of AOD is 0.09, 0.12; the mean of beta is 0.05, 0.13; the mean of a is 1.09, 0.06, respectively. At the Northeast of China, Hailun and Sanjiang, the mean of AOD is 0.14, 0.15; the mean of beta is 0.04, 0.06; the mean of a is 2.32, 1.58, respectively. At the desert region of North China, e.g., Fukang, Shapotou and Eerduosi, the range of averaged AOD is from 0.17 to 0.32; the range of averaged beta is from 0.09 to 0.19; the range of averaged a is from 0.68.to 1.28. At the forest areas, e.g. Changbai Mountain, Beijing forest and Xishuangbanna, the range of averaged AOD is from 0.19 to 0.42; the range of averaged beta is from 0.12 to 0.19; the range of averaged a is from 1.11 to 1.25. At agriculture areas, e.g. Shenyang, Fengqiu, Taoyuan and Yanting, the range of averaged AOD is from 0.34 to 0.68; the range of averaged beta is from 0.18 to 0.38; the range of averaged a is from 0.97 to 1.39. At the littoral areas and the lake of East China, e.g. Jiaozhou Bay, Shanghai City and Tai Lake, the range of averaged AOD is from 0.49 to 0.68; the range of averaged beta is from 0.21 to 0.29; the range of averaged a is from 1.24 to 1.37. At the inland cities, Beijing City and Lanzhou City, the mean of AOD is 0.47, 0.81; the mean of beta is 0.20, 0.45; the mean of a is 1.66, 0.89, respectively. The variations of aerosol properties at nineteen stations are explained in the paper.

Validation of MODIS aerosol retrievals and evaluation of potential cloud contamination in East Asia.

MODIS aerosol retrievals onboard Terra/Aqua and ground truth data obtained from AERONET (Aerosol Robtic Network) solar direct radiance measurements are collocated to evaluate the quality of the former in East Asia. AERONET stations in East Asia are separated into two groups according to their locations and the preliminary validation results for each station. The validation results showed that the accuracy of MODIS aerosol retrievals in East Asia is a little worse than that obtained in other regions such as Eastern U.S., Western Europe, Brazil and so on. The primary reason is due to the improper aerosol model used in MODIS aerosol retrieval algorithm, so it is of significance to characterize aerosol properties properly according to long-term ground-based remote sensing or other relevant in situ observations in order to improve MODIS retrievals in East Asia. Cloud contamination is proved to be one of large errors, which is demonstrated by the significant relation between MODIS aerosol retrievals versus cloud fraction, as well as notable improvement of linear relation between satellite and ground aerosol data after potential cloud contamination screened. Hence, it is suggested that more stringent clear sky condition be set in use of MODIS aerosol data. It should be pointed out that the improvement might be offset by other error sources in some cases because of complex relation between different errors. Large seasonal variation of surface reflection and uncertainties associated with it result in large intercepts and random error in MODIS aerosol retrievals in northern inland of East Asia. It remains to be a big problem to retrieve aerosols accurately in inland characterized by relatively larger surface reflection than the requirement in MODIS aerosol retrieval algorithm.