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Modeling study on seasonal variation in aerosol extinction properties over China

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Journal of Environmental Sciences 2014年第1期26卷 97-109页

作者： Yi Gao Meigen Zhang state key laboratory of atmospheric boundary layer physics and atmospheric chemistry Institute of Atmospheric Physics Chinese Academy of Sciences

To investigate the seasonal variation of aerosol optical depth （AOD）, extinction coefficient （EXT）, single scattering albedo （SSA） and the decomposed impacts from sulfate （SO42-） and black carbon （BC） over China, numerical experiments are conducted from November 2007 to December 2008 by using WRF-Chem. Comparison of model results with measurements shows that model can reproduce the spatial distribution and seasonal variation of AOD and SSA. Over south China, AOD is largest in spring （0.6-1.2） and lowest in summer （0.2-0.6）. Over north, northeast and east China, AOD is highest in summer while lowest in winter. The high value of EXT under 850 hPa which is the reflection of low visibility ranges from 0.4-0.8 km-1 and the high value area shifts to north during winter, spring and summer, then back to south in autumn. SSA is 0.92-0.94 in winter and 0.94-0.96 for the other three seasons because of highest BC concentration in winter over south China. Over east China, SSA is highest （0.92-0.96） in summer, and 0.88-0.92 during winter, spring and autumn as the concentration of scattering aerosol is highest while BC concentration is lowest in summer over this region. Over north China, SSA is highest （0.9-0.94） in summer and lowest （0.82-0.86） in winter due to the significant variation of aerosol concentration. The SOn2- induced EXT increases about 5%- 55% and the impacts of BC on EXT is much smaller （2%-10%）. The SO42--induced increase in SSA is 0.01-0.08 and the BC-induced SSA decreases 0.02-0.18.

关键词： seasonal variation AOD EXT SSA China WRF-Chem

Synergistic impacts of anthropogenic and biogenic emissions on summer surface O_3 in East Asia

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Journal of Environmental Sciences 2013年第3期25卷 520-530页

作者： Yu Qu Junling An Jian Li state key laboratory of atmospheric boundary layer physics and atmospheric chemistry Institute of Atmospheric PhysicsChinese Academy of Sciences

A factor separation technique and an improved regional air quality model （RAQM） were applied to calculate synergistic contributions of anthropogenic volatile organic compounds （AVOCs）,biogenic volatile organic compounds （BVOCs） and nitrogen oxides （NOx） to daily maximum surface O3（O3DM） concentrations in East Asia in summer （June to August 2000）.The summer averaged synergistic impacts of AVOCs and NOx are dominant in most areas of North China,with a maximum of 60 ppbv,while those of BVOCs and NOx are notable only in some limited areas with high BVOC emissions in South China,with a maximum of 25 *** result implies that BVOCs contribute much less to summer averaged O3DM concentrations than AVOCs in most areas of East Asia at a coarse spatial resolution （1×1） although global emissions of BVOCs are much greater than those of *** maximum total contributions of BVOCs can approach 20 ppbv in North China,but they can reach 40 ppbv in South China,approaching or exceeding those in some developed countries in Europe and North *** emissions in such special areas should be considered when O3 control measures are *** contributions among AVOCs,BVOCs and NOx significantly enhance O3 concentrations in the Beijing-Tianjin-Tangshan region and decrease them in some areas in South ***,the total contributions of BVOCs to O3DM vary significantly from day to day and from location to *** result suggests that O3 control measures obtained from episodic studies could be limited for long-term applications.

关键词： regional air quality model volatile organic compounds O3 factor separation technique synergistic contribution

Estimation of carbon dioxide flux and source partitioning over Beijing, China

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Journal of Environmental Sciences 2013年第12期25卷 2429-2434页

作者： Tao Song Yuesi Wang Yang Sun state key laboratory of atmospheric boundary layer physics and atmospheric chemistry Institute of Atmospheric Physics Chinese Academy of Sciences

The magnitude and partitioning of carbon dioxide emission from the urban area in Beijing, China was estimated based on a statistical approach. Results showed that the urban surface is a net source of CO2 to atmosphere. The main sources of CO2 are vehicles, which accounted for 75.5% and 38.9% of CO2 emission in summer and winter, respectively. At midday in summer, the CO2 uptake of-0.034 mg/（m^***） indicated that vegetation is an important sink of CO2 in summer. Comparison between the annual emission rates of CO2 from the statistical approach and that directly measured by the eddy covariance technique implies that a bottom-up emission approach is a viable means to estimate CO2 emission in an urban area.

关键词： C02 emission source eddy covariance

Variation Characteristics of Ultraviolet Radiation over the North China Plain

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Advances in atmospheric Sciences 2014年第1期31卷 110-117页

作者： HU Bo WANG Yuesi state key laboratory of atmospheric boundary layer physics and atmospheric chemistry Institute of Atmospheric Physics Chinese Academy of Sciences

In situ measured data of broadband solar radiation （Rs） and ultraviolet （Uv） radiation were used to investigate the spa- tiotemporal variation properties of Uv radiation and the ratio of Uv radiation to Rs over the North China Plain （NCP）. Based on the analysis, an empirical model for estimating Uv radiation under all weather conditions in this region was developed. The results showed that the annual Uv radiation over the NCP ranges from 0.38-0.52 MJ m^-2 d^-1. The highest value during the study period was recorded at the Changwu site, which is located near the margin of the Loess Plateau, while the lowest value appeared at the station in Beijing. The seasonal variation pattern of the ratio of Uv radiation to Rs is similar to that of Uv radiation; namely, the highest value appears in August and then decreases gradually until the lowest value appears in November. A small increasing trend in the Uv radiation levels and the ratio of Uv radiation to Rs was observed over the NCP. The evaluation results showed that the empirical estimation model can be widely used to estimate Uv radiation under all atmospheric conditions. The relative error between the modeled and measured daily values were within ± 15%.

关键词： ultraviolet radiation North China Plain increasing trend parameterization method

Modeling nitrate aerosol distributions and its direct radiative forcing in East Asia with RAMS-CMAQ

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Particuology 2013年第3期11卷 256-263页

作者： Xiao Han Meigen Zhang Baorong Zhou state key laboratory of atmospheric boundary layer physics and atmospheric chemistry Institute of Atmospheric PhysicsChinese Academy of Sciences Xinghua Meteorological Bureau

The geographical and seasonal characteristics in nitrate aerosol and its direct radiative forcing over East Asia are analyzed by using the air quality modeling system RAMS-CMAQ coupled with an aerosol optical properties/radiative transfer module. For evaluating the model performance, nitrate ion concentration in precipitation, and mixing ratios of PMl0, and some gas precursors of aerosol during the whole year of 2007 are compared against surface observations at 17 stations located in Japan, Korea, and China, and the satellite retrieved NO2 columns, The comparison shows that the simulated values are generally in good agreement with the observed ones. Simulated monthly averaged values are mostly within a factor of 2 of the measurements at the observation stations. The distribution patterns of NO2 from simulation and satellite measurement are also similar with each other. Analysis of the distribution features of monthly and yearly averaged mass concentration and direct radiative forcing （DRF） of nitrate indicates that the nitrate aerosol could reach about 25-30% of the total aerosol mass concentration and DRF in Sichuan Basin, Southeast China, and East China where the high mass burden of all major aerosols concentrated. The highest mass concentration and strongest DRF of nitrate could exceed 40 μg/m^3 and -5 Wire2, respectively. It also indicates that other aerosol species, such as carbonaceous and mineral particles, could obviously influence the nitrate DRF for they are often internally mixed with each other.

关键词： Nitrate aerosolDirect radiative forcing CMAQEAN ET AOD

Dust Storm Ensemble Forecast Experiments in East Asia

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Advances in atmospheric Sciences 2009年第6期26卷 1053-1070页

作者：朱江林彩燕王自发 state key laboratory of atmospheric boundary layer physics and atmospheric chemistry Institute of Atmospheric Physics Chinese Academy of Sciences

The ensemble Kalman filter （EnKF）, as a unified approach to both data assimilation and ensemble forecasting problems, is used to investigate the performance of dust storm ensemble forecasting targeting a dust episode in the East Asia during 23-30 May 2007. The errors in the input wind field, dust emission intensity, and dry deposition velocity are among important model uncertainties and are considered in the model error perturbations. These model errors are not assumed to have zero-means. The model error means representing the model bias are estimated as part of the data assimilation process. Observations from a LIDAR network are assimilated to generate the initial ensembles and correct the model biases. The ensemble forecast skills are evaluated against the observations and a benchmark/control forecast, which is a simple model run without assimilation of any observations. Another ensemble forecast experiment is also performed without the model bias correction in order to examine the impact of the bias correction. Results show that the ensemble-mean, as deterministic forecasts have substantial improvement over the control forecasts and correctly captures the major dust arrival and cessation timing at each observation site. However, the forecast skill decreases as the forecast lead time increases. Bias correction further improved the forecasts in down wind areas. The forecasts within 24 hours are most improved and better than those without the bias correction. The examination of the ensemble forecast skills using the Brier scores and the relative operating characteristic curves and areas indicates that the ensemble forecasting system has useful forecast skills.

关键词： dust storm ensemble forecast data assimilation bias correction

Interannual variations of the air-sea carbon dioxide exchange in the different regions of the Pacific Ocean

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Acta Oceanologica Sinica 2013年第3期32卷 71-79页

作者： LI Yangchun XU Yongfu state key laboratory of atmospheric boundary layer physics and atmospheric chemistry Institute of Atmospheric PhysicsChinese Academy of Sciences

Interannual variations of the air-sea CO2 exchange from 1965 to 2000 in the Pacific Ocean are studied with a Pacific Ocean model. Two numerical experiments are performed, including the control run that is forced by climatological monthly mean physical data and the climate-change run that is forced by interannually varying monthly mean physical data. Climatological monthly winds are used in both runs to calculate the coefficient of air-sea CO2 exchange. The analysis through the differences between the two runs shows that in the tropical Pacific the variation of export production induced by interannual variations of the physical fields is negatively correlated with that of the air-sea CO2 flux, while there is no correlation or a weak positive correlation in the subtropical North and South Pacific. It indicates that the variation of the physical fields can modulate the variation of the air-sea CO2 flux in converse ways in the tropical Pacific by changing the direct transport and biochemical process. Under the interannually varying monthly mean forcing, the simulated EOF 1 of the air-sea CO2 flux is basically consistent with that of sea surface temperature （SST） in the tropical Pacific, but contrary in the two subtropical Pacific Ocean. The correlation coefficient between the regionally integrated air-sea CO2 flux and area-mean SST shows that when the air-sea CO2 flux lags SST by about 5 months, the positive coefficient in the three regions is largest, indicating that in the tropical Pacific or on the longer time scale in the three regions, physical processes control the fiux-SST relationship.

关键词： air-sea carbon dioxide exchange surface temperature export production interannual varia-tions Pacific Ocean

Reductions of PM_(2.5) in Beijing-Tianjin-Hebei Urban Agglomerations during the 2008 Olympic Games

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Advances in atmospheric Sciences 2012年第6期29卷 1330-1342页

作者：辛金元王跃思王莉莉唐贵谦孙扬潘月鹏吉东生 the state key laboratory of atmospheric boundary layer physics and atmospheric chemistry Institute of Atmospheric PhysicsChinese Academy of Sciences

The atmospheric Environmental Monitoring Network successfully undertook the task of monitoring the atmospheric quality of Beijing and its surrounding area during the 2008 Olympics. The results of this monitoring show that high concentrations of PM2.5 pollution exhibited a regional pattern during the monitoring period （1 June-30 October 2008）. The PM2.5 mass concentrations were 53 μg m-3, 66 p.g m-3, and 82 μg m-3 at the background site, in Beijing, and in the Beijing-Tianjin-Hebei urban agglomerations, respectively. The PM2.5 levels were lowest during the 2008 Olympic Games （8-24 August）： 35μg m-3 at the background site, 42 μg m-3 in Beijing and 57 μg m-3 in the region. These levels represent decreases of 49%, 48% and 56%, respectively, compared to the prophase mean concentration before the Olympic Games. Emission control measures contributed 62% 82% of the declines observed in Beijing, and meteorological conditions represented 18%-38%. The concentration of fine particles met the goals set for a ＂Green Olympics.＂

关键词： PM2.5 the 2008 Olympic Games the urban agglomerations the network

A New Carrier Gas Type for Accurate Measurement of N_2O by GC-ECD

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Advances in atmospheric Sciences 2010年第6期27卷 1322-1330页

作者：王迎红王跃思凌宏 state key laboratory of atmospheric boundary layer physics and atmospheric chemistry Institute of Atmospheric PhysicsChinese Academy of Sciences

The accurate measurement of concentration is the basis for determining emission sources and sinks of nitrous oxide （N2O）. The detection of N2O showed that the presence of carbon dioxide （CO2） biased the N2O response when pure nitrogen （N2） was used as a carrier gas for gas chromatography （GC） equipped with an electron capture detector （GC-ECD）. In this study, laboratory experiments were carried out to explore how the presence of CO2 interferes with the accurate determination of N2O. The aims were to address the extent of the influence to try and explain the underlying mechanism, and to uncover technical options for solving the problem. Three GC carrier gases are discussed： pure nitrogen （DN）; a mixture of argon and methane （AM）; and a high concentration CO2, which was introduced into the ECD cell with a low flow rate based on DN （DN-CO2）. The results show that when DN was used, the existence of CO2 in the ECD cell greatly enhanced the response of N2O, which increased with CO2 content and remained constant when the content reached a limit. Comparisons between the three methods show that the DN method is defective for the accurate determination of N2O. The bias is caused by different electron capture mechanisms of CO2 and N2O and depends heavily on the detector temperature. New GC carrier gas types with make-up gases that can remove the CO2-induced influence, such as the DN-CO2 and DN-CH4 methods reported in this paper, are recommended for the accurate measurement of N2O.

关键词： nitrous oxide gas chromatography electron capture detector carbon dioxide overestimation