大气NO2柱浓度多轴差分吸收光谱测量技术及应用

介绍了以太阳散射光为光源的多轴差分吸收光谱技术（Multi-Axis Differential Optical Absorption Spectroscopy,简称MAX-DOAS）,以及MAX-DOAS仪器试验应用.试验中选取中午仪器测量的天顶散射光光谱为参考光谱即Fraunhofer参考光谱,并将测量光谱进行消噪、波长校准以及去除Fraunhofer结构处理.利用分子吸收光学厚度和Ring效应光学厚度对处理后的测量光谱进行最小二乘法拟合,反演出了大气NO2差分斜柱浓度（Differential Slant Column Densities,简称DSCD）.分析了天津武清NO2的差分斜柱浓度反演结果,用简单快捷的几何法将NO2差分斜柱浓度转化成对流层垂直柱浓度（Vertical Column Densities,简称VCD）.研究表明,MAX-DOAS可以有效地监测污染地区对流层NO2的垂直柱浓度.     

长光程与传统点式污染气体监测技术对比

结合2类大气成分观测仪器的技术特点,对OPSIS AB DOAS系统和Thermo SCIENTIFIC EMS系统分别监测的南京郊区2009年冬季和2010年春季O3、NO2、SO2质量浓度数据进行了质量控制和分析对比,简要分析了这3种气体浓度的季节变化特征．对2009年秋季分别采用2种仪器观测的南京城区和郊区的污染情况进行了对比,分析了城郊差异．结果表明:2套系统对相同气体的测量结果相关性较好,DOAS系统的测量值受大气中水汽和气溶胶影响较大,普遍高于EMS系统,绝对值相差范围在14％～25％之间;南京郊区冬季大气中SO2和NO2质量浓度较高,O3质量浓度较低,春季反之;NO2质量浓度曲线与O3呈负相关;秋季城区NO2质量浓度较高,日变化呈双峰型,郊区呈单峰型;城郊O3日变化均呈单峰型,城区日变化幅度较大;SO2日变化在城区呈单峰型,在郊区呈双峰型．     

辽宁农村代表区域降水离子组成及与气态污染物相关性

对辽宁农村代表区域站点——辽中县马龙村观测站2007年2月至2008年1月酸雨、气态污染物浓度观测资料进行了研究。结果表明：辽中站降水的化学组成阴离子主要为SO4^2-和NO3-阳离子主要为NH4和Ca2＋,SO4^2-／NO3-比值为2．9．Na＋／Cl-比值较大,大于1。各种离子浓度冬春季高,夏秋季较低,表明研究区域降水酸化与污染关系不显著。实测的9种主要阴离子、阳离子总浓度比（∑阴离子／∑阳离子）与降水pH值相关性不高,表明目前酸雨研究观测的主要9种阴阳离子不能完全包括降水中的离子组成。降水酸性与近地面污染气体浓度相关各异,pH与NOx、CO、NO2和O3浓度有较明显的负相关,与SO2浓度负相关不明显;降水pH值与颗粒物等碱性污染物浓度正相关明显。降水中主要致酸离子SO4^2-和NO3-的浓度与相应酸性气体污染物SO2和NOx近地面浓度的相关不明显。     

热带深对流云对CO、NO、NOx和O3的垂直输送作用

利用2005年11月至2006年2月ACTIVE (Aerosol and Chemical Transport in tropIcal conVEction) 外场试验期间在澳大利亚北部达尔文地区取得的CO、O3、NO和NOx飞机探测资料, 并结合HYSPLIT后向轨迹模式结果, 分析这几种气体成分在对流卷云砧内外的分布情况, 并探讨热带深对流云对于污染气体的垂直输送作用。分析结果显示, 在孤立对流云卷云砧中, 云砧内部O3、NO、NOx浓度均大于云外; 而CO则不同, 只有在近地面浓度高时才如此, 在近地面浓度较小时, 卷云砧内部的浓度反而小于云外。进一步分析造成这两类气体分布差异的原因, 发现CO主要借助深对流云将对流层下层以及对流云周围环境中的CO夹卷并动力垂直输送到对流云顶部卷云砧中, 而对于O3、NO和NOx来说, 除了上述作用以外, 还可能与对流云内部其他物理机制(如闪电), 造成新的O3、NO和NOx有关, 这些新生气体随着风暴内部强烈的上升气流被最终输送进云砧中。     

北京奥运会期间NO2浓度降低原因分析

2002～2008年,北京市城区和近郊8月的NO2月均浓度大体呈现逐年下降趋势,其中前5年二者均以每年约10%的降幅下降,2008年发生显著下降,降幅达40%左右。利用嵌套网格空气质量模式系统(NAQPM/IAP),采用敏感性试验方法,评估了气象条件与污染控制措施对北京奥运会期间大气NO2浓度降低的影响,评估不同污染控制措施对NO2浓度降低的作用。研究结果表明,污染控制措施是NO2浓度降低的主要影响因素,其中面源的污染控制措施对于NO2浓度降低的作用最明显。     

北京上甸子本底站2003年秋冬季痕量气体浓度变化特征

2003年9月至2004年2月在北京上甸子区域大气污染本底监测站(117°07′E,40°39′N,海拔293.9 m)开展了对大气中痕量气体的连续在线监测,获得了NO、NO2、SO2、CO和O3等气体组分的变化特征、变化规律和浓度水平。初步分析表明,NO、NO2、SO2、CO和O3有明显的日变化和月变化特征。O3浓度在秋季较高,冬季较低;NO、NO2和SO2冬季出现浓度高值。探讨了O3和痕量气体与气象因子的关系。O3与NO、NO2、NOx、CO和SO2皆为负相关,CO与NOx和SO2具有较好的相关性。本底站痕量气体浓度与同期观测的城区污染物浓度相比其变化趋势基本呈同位相。     

2007-2008年南京江北工业区大气降水化学特征

2007年3月-2008年9月在南京市江北地区南京信息工程大学采集有效降水样品共48个,测量了降水的pH值和电导率,用离子色谱仪分析检测了降水样品的阴、阳离子的质量浓度。结果表明：2007年的酸雨频率为44．5％,2008年酸雨频率为59．3％,南京江北工业区降水的酸性及酸化频率都有所增高;2007-2008年大气降水与2005-2006年所测数据相比较,NO3-的质量浓度略有增长,NH4＋的质量浓度有了较大幅度的增长;研究区域SO4／NO。的实验数据表明,硫污染特征有所减弱,氮氧化物污染逐渐突出,表现出燃煤污染与汽车尾气污染并存的过渡型大气污染特征。     

六种HFCs的辐射强迫与全球增温潜能

采用最新分子吸收数据集HITRAN2004中6种氢氟碳化物（HFCs）的吸收截面数据,建立了它们的相关K-分布的辐射计算方案,研究了这些长寿命温室气体浓度变化引起的辐射强迫,比较了它们的全球增温潜能。结果表明,从1750年到2005年由于这些气体浓度变化引起的总的辐射强迫约为0、0066Wm^-2,未来100a的辐射强迫结果说明它们对未来全球变暖的贡献不容忽视。     

北京城区大气边界层空气污染特征观测研究

2001年1～3月共分3期,在北京城市地区大气边界层进行了大气化学和气象现埸观测.结果表明北京城市低层大气中主要的气体污染物是NOx,其次为SO2;各高度SO2和NOx之间的关系有较好的一致性,NOx大约为SO2浓度的2倍或2倍以上;污染源排放是造成北京城市低层大气空气污染严重与否的主要原因之一;同一季节中空气污染状况很大程度上取决于天气条件;NO2/NO和NO之间有着较好的负幂指数相关关系;近地层不同高度和不同地点观测到的大气污染物随时间变化趋势有较好的一致性.     

瓦里关大气本底观象台CO2、CH4观测过程的质量控制

以中国大气本底基准观象台的温室气体(CO2、CH4)观测仪器为例,从仪器运行的稳定性和各级标准气体标定两个方面介绍了温室气体观测数据的质量控制方法.结果表明,瓦里关大气本底台的CO2、CH4观测仪器运行稳定,观测数据具有很高的精确度和可信度.经过严格质量控制的温室气体实时测量数据报送到世界气象组织下属的温室气体数据中心,成为各国科学家分析欧亚大陆温室气体本底浓度的主要依据.     

地基曙暮光光谱观测反演平流层O3和NO2柱含量

用差分光学吸收光谱(DOAS)方法,从曙暮光天顶散射可见光光谱资料反演了北京上空的O3和NO2柱含量,并对反演结果进行了验证和误差分析.斜柱含量的反演采用了线性和非线性最小二乘拟合方法,拟合时考虑了O3、NO2和H2O的吸收、Ring效应和散射的影响;斜柱含量除以空气质量因子转换成垂直柱含量.空气质量因子的计算使用伪球面DISORT辐射传输模式.O3和NO2总量的检验分别用北京的Dobson O3资料和卫星SAGE Ⅱ的NO2廓线资料.反演的O3总量与Dobson O3总量相比偏差小于10%;NO2总量与SAGE Ⅱ的偏差约20%.     

臭氧吸收参数数据库精度检验和验证

利用国际权威期刊上发表的臭氧吸收截面观测数据,检验和验证了现有的紫外正演模式TOMRAD臭氧吸收参数数据库。结果表明,在Hartley臭氧吸收带上,观测数据与数据库参数吻合状况很好;而在Huggins臭氧吸收带上,观测数据与数据库参数在部分波长上存在较大偏差,某些波长上的偏差超过50%。鉴于此,FY-3紫外臭氧探测仪资料处理计算中,选取臭氧吸收参数,必须特别慎重。     

光吸收对冰晶粒子散射相函数的影响

本文利用射线跟踪法对冰晶粒子散射、吸收进行了研究。从理论上对一些常见的近似处理方法进行了讨论，计算了长为300μm，半径为30μm的六棱柱状冰晶粒子在不同波段的光散射相函数以及在波长2.2μm时，五种不同大小冰晶粒子的单次散射反照率。结果表明，即使在有吸收情况下，Snell公式和Lambert公式仍是近似成立的，而吸收效应对散射相函数有明显影响。     

Single scattering from frozen hydrometeors at microwave frequencies

Scattering of electromagnetic waves from homogeneous or coated spheres can be computed in a mathematically exact way using the Mie theory. Therefore, for many approaches in remote sensing, frozen hydrometeors are parameterized as ice spheres. However, many frozen hydrometeors have non-spherical overall shapes and lack a spherically symmetric internal structure. They exist in a huge variety of shapes and exhibit different mixtures of ice, water and air. Therefore it is desirable to accurately compute scattering from non-spherical particles in order to clearly understand the effect the shape of a hydrometeor has on its scattering pattern.In this study, single scattering parameters like scattering cross section, absorption cross section, and asymmetry factor were calculated for frozen hydrometeors using the Discrete Dipole Approximation (DDA). The particles were modeled as hexagonal plates, columns, needles and dendrites by applying known dimensional relationships. The calculations were carried out over a wide range of centimeter and millimeter-wavelengths (1 GHz to 300 GHz), since millimeter-wave radiometers are highly sensitive to scattering by frozen hydrometeors in the atmosphere.The study results show that for size parameters < 1 (a ratio between wavelength and particle size) the scattering cross section of randomly orientated ice crystals is close to that of an equal volume ice sphere. Absorption cross section and asymmetry factor of non-spherical particles however are up to twice as high as that of equal volume ice spheres. Further the influence of the assumed model for the refractive index of ice at microwave wavelengths on the scattering parameters is investigated.     

OH-initiated degradation of several hydrocarbons in the atmosphere simulation chamber SAPHIR

Degradation of isoprene, m-xylene, n-octane, propene, and methacrolein by hydroxyl radicals has been studied in the simulation chamber SAPHIR under burden of trace gases as they are typical for the moderately polluted planetary boundary layer. Measured time series of the hydrocarbon mixing ratios and the OH concentrations were used to determine the rate constants. The hydrocarbons were measured with gas chromatography and proton transfer reaction mass spectrometry. OH was measured with the Jülich DOAS (differential optical absorption spectroscopy) instrument. In all cases except methacrolein good agreement was found with the reference rate constants taken from the Master Chemical Mechanism (MCM3.1). The data for methacrolein are consistent with the results of Karl et al. (J. Atmos. Chem 55, 2006, doi:) who reported a 12% smaller value. The degradation of hydrocarbons provides an independent method to analyse precision and accuracy of the OH measurements. A precision of better than 4% over a period of nearly 4 months was found. The accuracy is within the limitations given by the light absorption cross section of OH. Both results are consistent with earlier results by Hausmann et al. (J. Geophys. Res. 102:16011–16022, 1997).     

Validating extinction calculations from Lidar signals within the planetary boundary layer by signal simulations

Summary This paper describes the comparison of calculated extinction coefficients from Lidar signals by the known Fernald-Klett inversion method with Lidar signal simulations. A ground-based Differential Absorption Lidar was employed in two studies measuring O₃ and SO₂ within the planetary boundary layer (PBL). By calculating extinction coefficients additional information about the PBL structure is obtained. As commonly used numerical inversion methods are limited to the knowledge of necessary boundary conditions, Lidar signal simulations are used for their estimation. Furthermore, comparing results of the inversion method with Lidar signal simulations validates calculated extinction coefficients.     

Intercomparison of NO_x, SO_2, O_3, and Aromatic Hydrocarbons Measured by a Commercial DOAS System and Traditional Point Monitoring Techniques

A field-based Intercomparison study of a commercial Differential Optical Absorption Spectroscopy (DOAS) instrument (OPSIS AB, Sweden) and different point-sample monitoring techniques (PM, based on an air monitoring station, an air monitoring vehicle, and various chemical methods) was conducted in Beijing from October 1999 to January 2000. The mixing ratios of six trace gases including NO, NO2, SO2, O3, benzene, and toluene were monitored continuously during the four months. A good agreement between the DOAS and PM data was found for NO2 and SO2. However, the concentrations of benzene, toluene, and NO obtained by DOAS were significantly lower than those measured by the point monitors. The ozone levels monitored by the DOAS were generally higher than those measured by point monitors. These results may be attributed to a strong vertical gradient of the NO-O3-NO2 system and of the aromatics at the measurement site. Since the exact data evaluation algorithm is not revealed by the manufacturer of the DOAS sys     

用太阳及天光光度计进行大气臭氧探测

在紫外光谱区，大气臭氧有较丰富的吸收带结构。作者用自制的太阳及天光光度计测量直射阳光、直射月光和曙暮光的紫外吸收光谱，并用带吸收法计算臭氧垂直柱总量及斜程含量。文中介绍了观测和计算方法，并给出北京地区晴朗天气条件下观测的初步结果。     

Intercomparison of NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>, SO<Subscript>2</Subscript>, O<Subscript>3</Subscript>, and aromatic hydrocarbons measured by a commercial DOAS system and traditional point monitoring techniques

A field-based intercomparison study of a(DOAS) instrument (OPSIS AB, Sweden) andcommercial Differential Optical Absorption Spectroscopydifferent point-sample monitoring techniques (PM, basedon an air monitoring station, an air monitoring vehicle, and various chemical methods) was conducted inBeijing from October 1999 to January 2000. The mixing ratios of six trace gases including NO, NO2, SO2,03, benzene, and toluene were monitored continuously during the four months. A good agreement betweenthe DOAS and PM data was found for NO2 and SO2. However, the concentrations of benzene, toluene,and NO obtained by DOAS were significantly lower than those measured by the point monitors. Theozone levels monitored by the DOAS were generally higher than those measured by point monitors. Theseresults may be attributed to a strong vertical gradient of the NO-O3-NO2 system and of the aromatics atthe measurement site. Since the exact data evaluation algorithm is not revealed by the manufacturer ofthe DOAS system, the error in the DOAS analysis can also not be excluded.