广州黄埔工业区近地层气溶胶分级水溶性成分的物理化学特征

通过对在黄埔工业区收集的气溶胶样品的质量谱与水溶性离子成分谱的分析表明 :总气溶胶质量与诸离子浓度均明显高于华南大陆的值 ,其分布表现为明显的 3峰分布 ,气溶胶中以 SO2 - 4,NO- 3 ,Ca2 ,NH 4 为主要的离子成分 ;较之华南陆地测站 ,除离子浓度成倍增加外 ,SO2 - 4的浓度占了阴离子含量的绝大部分 ,NO- 3 ,NH 4 的含量比重显著增加 ,以及 NO- 3 ,SO2 - 4,NH 4 ,K 较多地存在于细粒态粒子中是其主要特点。     

Experimental study of the effect of temperature on ion cluster formation using ion mobility spectrometry

Ion mobility spectrometry offers a robust and effective technique to study ion clusters in ambient conditions. Here, we have experimentally studied the influence of temperature on the positive ion cluster formation of 2-propanol vapor in air, along with parallel measurements for n-butyl acetate vapor in air. For both of these low proton affinity compounds in the ppm concentration range, temperatures below 0 °C tend to favor formation of dimers and trimers. The measurements indicate that approximate estimations for the fractions of these n-mers (n > 1) in the ion spectra, can be obtained by classical theory for ion induced nucleation. Presence of natural background vapors however slightly blurs the data, especially for the fraction of monomers, so that accurate prediction of the fractions of n-mers in the spectra would require more accurate information on the gas composition. The findings concerning thermal behavior of ions help to understand better ion phenomena also in field conditions.     

The intracloud/cloud-to-ground lightning ratio in Southeastern Brazil

The intracloud to cloud-to-ground lightning flash ratio (Z) has been estimated for the first time in Southeastern Brazil and in the tropical region using the Lightning Imaging Sensor (LIS) and Brazilian lightning detection network (BrasilDat) lightning data obtained from 1999 to 2005. Geographical variations of Z and their relation to elevation, latitude, precipitation, total lightning density and percentage of positive CG lightning will be discussed. Daily variations of Z will also be presented. The results suggest that Z values are similar to studies outside the tropics and that are influenced by orographic features.     

Organosulfates – A New Component of Humic-Like Substances in Atmospheric Aerosols?

Ion trap mass spectrometry (ITMS) was used to obtain further qualitative information about the chemical composition of humic-like substances (HULIS) in atmospheric particulate matter. Particles ≤10 μm (PM₁₀) were collected on quartz fiber filters for 24 h in the region of Basel (Switzerland) and extracted with water. HULIS were separated from inorganic salts by size exclusion chromatography (SEC) and detected by electrospray ionization in the negative ion mode (ESI(−)). Series of consecutive fragment ion spectra (MSⁿ) were recorded by ITMS. Full scan mass spectra of the extracts showed a mass distribution pattern characteristic for HULIS. Different molecular ions were selected from this pattern for further fragmentations. Among them the molecular ion m/z 299 was considered as representative and intensively studied. Many MS² and MS³ fragment spectra contained a fragment m/z 97 and a neutral loss of 80 u. Time-of-flight (TOF) MS and deuterium exchange experiments identified m/z 97 as hydrogen sulfate. MS² and MS³ fragment spectra supported the existence of sulfate covalently bound to HULIS. The fragmentation behavior of sulfated HULIS could be confirmed by model compounds.     

青藏高原大气气溶胶研究进展

文中综述了近30年来青藏高原大气气溶胶的研究现状,包括青藏高原大气气溶胶光学厚度、气溶胶面密度等的时空变化特征,大气气溶胶化学成分分析及气候效应的研究等。大多利用卫星、激光雷达及地面采样等资料分析研究气溶胶。青藏高原大气气溶胶研究已经取得了显著进展。文中主要综述了该领域的研究成果,并对其今后的研究进行了展望。      

Dry-air boundary conditions for correction of eddy flux measurements

For measurements of eddy fluxes in the atmospheric boundary layer of gases (such as CO₂) whose average concentration is very large compared to the fluctuations, corrections for air density fluctuations are required. With the boundary condition of no flux of dry air at the surface, the evaporation correction to eddy fluxes is 2.6 times larger than has been estimated with the boundary condition of no mass flux at all at the surface. The heat flux correction is also increased by a few per cent.     

Biomonitoring of Element Deposition Using Mosses in the 2000 French Survey: Identifying Sources and Spatial Trends

In the year 2000, the elemental composition of mosses collected from 528 French sites has been studied as part of the 2000 European Moss Survey. Five moss species were collected: Scleropodium purum (56%), Pleurozium schreberi (18%), Hypnum cupressiforme (18%), Thuidium tamariscinum (4.5%.) and Hylocomium splendens (3.5%). Mosses were kept whole for analysis, including green and brownish parts. Summary statistics on element concentrations (Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Na, Ni, P, Pb, Rb, Sr, V and Zn), and comparisons made with data from the other 27 participating European countries are shown here. The sources of these elements are identified using calculations of enrichment factors (EF) and principal component analysis (PCA). Finally, the spatial distribution in France of 10 elements is also shown, using maps underscoring areas showing highest concentration levels for each metal.     

Size-Resolved Aerosol Characterization for a Polluted Episode at the IfT Research Station Melpitz in Autumn 1997

Inorganic ions, organic carbon (OC), elemental carbon (EC) and a variety of organic single species in airborne particles have been determined at the research station of the Leibniz – Institut für Troposphärenforschung (IfT) in Melpitz (Germany) in autumn 1997.Samples of eight selected measurement events were divided in two groups in order to investigate differences in the chemical composition of particles originating from southwesterly (SW – developed EU countries) or from easterly directions (E – less developed eastern countries). Differences between these two groups were tested statistically by Student's t-test.Five stage cascade impactor samples show nitrate as most abundant in the accumulation mode in the SW group. EC and sulphate show the most abundant mass fractions in the E group. That can be considered as a consequence of domestic coal heating and coal-fired power plant emissions in the region of westerly Poland, northern Czech Republic and easterly Germany. Higher nitrate concentrations in the SW group can be explained by stronger NO _x emissions caused by the leeward plume of the conurbation of Leipzig, as well as by the still higher traffic density in western Germany.The methane sulphonic acid (MSA) mass fraction was higher for SW air masses in accumulation mode particles, probably indicating marine origin. Succinic acid also showed higher mass fractions for the SW group. This could be caused by primary emission in automobile exhaust gases and photochemical formation during transport from SW. Indeed, during SW sampling, solar radiation intensity was higher than during E sampling.The observed differences in the particle composition are an expression of the still existing technology gradient in Europe. Future campaigns could show the development to a joint economy with smaller differences in anthropogenic emissions.     

Stable Carbon Isotope Ratios and the Photochemical Age of Atmospheric Volatile Organic Compounds

Abstract

The dependence of ozone formation on the mixing ratios of volatile organic compounds (VOCs) and nitrogen oxides (NO_x) has been widely studied. In addition to the atmospheric levels of VOCs and NO_x, the extent of photochemical processing of VOCs has a strong impact on ozone levels. Although methods for measuring atmospheric mixing ratios of VOCs and NO_x are well established and results of those measurements are widely available, determination of the extent of photochemical processing of VOCs, known as photochemical age (PCA), is difficult. In this article a recently developed methodology for the determination of PCA for individual compounds based on the change in their stable carbon isotope composition is used to investigate the dependence between ozone and VOC or NO_x mixing ratios at a rural site in Ontario, Canada, during fall and winter. The results show that under these conditions the variability in VOC mixing ratios is predominantly a result of the varying impact of local emissions and not a result of changes in the extent of atmospheric processing. This explains why the mixing ratio of ozone shows no systematic dependence on the mixing ratios of VOCs or NO_x in this environment and at this time of the year.     

Effects of seed particle size and composition on heterogeneous nucleation of n-nonane

Heterogeneous nucleation of supersaturated n-nonane vapour on seed particles of different size and composition has been investigated using a fast expansion chamber. Monodisperse seed particle sizes were ranging from about 4 nm up to about 24 nm in diameter. By using different types of particle generators WO_x, Ag and (NH₄)₂SO₄ particles were generated. For direct comparison between different particle compositions overlapping sizes have been generated for WO_x and Ag at about 7 nm particle diameter as well as for Ag and (NH₄)₂SO₄ at about 15 nm. Nucleation temperature was kept constant at about 278 K. Experimental data were compared to Kelvin equation and Fletcher theory including the effect of line tension. It was found that heterogeneous nucleation of n-nonane seems to be independent of seed particle composition and starts well below the Kelvin curve. Good agreement was achieved with Fletcher theory including the effect of line tension.     

Computational parameter estimation for a maize crop

During a whole growing season, the evolution of the displacement height, d, and roughness length, z ₀, of a maize crop has been estimated by a measurement programme. The results have been used to check different types of existing models to calculate these parameters from canopy characteristics only; a simple geometric model and two matching models have been investigated. A geometric model is based on geometric features of the surface only. After a simple modification, the geometric model gives good results for the displacement height as well as for the roughness length.A matching model, based on gradient-diffusion theory, yields good results for the displacement height. The roughness parameter, however, is overestimated by 17%. By a simple modification, the model results could be improved considerably.A matching model, based on a second-order closure procedure, yields excellent results for the displacement height and good results for the roughness length. But it appears that, when applying this model, the plant density index and plant area density distribution as a function of height must be well known.     

New aerosol particle formation via certain ion driven processes

Ions can speed up the formation of aerosol particles. The former studies have mainly concerned on the role of the ion charge itself. We have studied the possible (additional) role of the actual small air ion spectrum shape, and the quantitative role of ion–ion recombination pathway. By means of our ion evolution model, formation of new species (H₂SO₄)_n(NH₃)_m(HNO₃)_k via ion–ion recombination was investigated. The model shows how the generation rate of the new species depends on the concentrations of H₂SO₄ and NH₃, and how it depends on the tropospheric background aerosol situation. The rate can be up to a few new neutral complexes per cubic centimeter and per second. New particle generation via ion–ion recombination provides an extra channel, especially for the clean atmosphere. Former results have shown that such situations are often present in Antarctica. Our aerosol spectrum measurements reveal a number of similar non-Antarctic results. Sometimes, such situations are followed by aerosol bursts, which may be (partly) due to an ion–ion recombination channel.     

星载双频云雷达的云微物理参数反演算法研究

使用星载雷达模拟器输出的模拟数据,为星载双频云雷达选择了最佳的频点组合,并开展了双频联合反演云微物理参数的算法研究。结果表明:（1）在位于大气窗口的6组频点组合中,94/220 GHz的组合对滴谱参数的微小变化较为敏感,有利于进行双频的联合反演。综合考虑不同频点的探测能力、衰减以及工业部门的制造水平后,认为94/220 GHz可以作为未来星载双频测云雷达的探测频点。（2）双频反演中最核心的双波长比（DWR）和体积中值直径（D₀）的关系与冰晶粒子密度相关。当密度随着粒子直径变化时,DWR随着D₀单调递增,当粒子密度固定不变时,DWR-D₀曲线可能会出现非单调变化,从而使得固定密度时的反演比变密度时更加复杂。（3）后向迭代的双频反演算法同样适用于94/220 GHz进行云微物理参数的反演,并且对模拟数据的反演精度较高。此外,反演精度受到系统噪声以及定标精度的影响,为了满足反演精度的要求,系统噪声和定标误差应该控制在1 dBz以内。      

On the horizontal density ratio in the upper ocean

The horizontal density ratio in the upper ocean is examined using SeaSoar data collected over the last 15 years in the Pacific, Atlantic, and Indian Oceans. The horizontal density ratio R is defined to be the ratio of the relative effect of temperature and salinity on density. A front with a horizontal density ratio of 1 is said to be compensated since temperature and salinity gradients compensate in their effect on density. The statistics of density ratio are examined through calculation of conditional probability density functions. Case studies from each of the oceans elucidate processes affecting the density ratio. Global distributions of density ratio are calculated as functions of mixed-layer depth, distance below the mixed layer, and magnitude of thermohaline variability. Compensation is found in all oceans, on 3–4 km horizontal scales, when the mixed layer is deep and significant thermohaline variability exists. The tendency for compensation is stronger as mixed-layer depth increases. Conversely, compensation is not typical in shallow mixed layers, or when thermohaline variability is weak. The thermocline density ratio is found to be 2, in agreement with previous observational studies, and consistent with the process of salt fingering. The transition from R=1 in the mixed layer to R=2 in the thermocline is sharp when the mixed layer is deep. The ubiquity of compensation in the mixed layer is consistent with recent theory that suggests horizontal eddy diffusivity is a growing function of density gradient.     

Tracer experiments with turbulently dispersed air ions

Unipolar air ions released into the wind constitute a tracer which can be measured with high resolution. An ion source produces a cloud with homogeneous charge density, insensitive to source strength, dependent on time since formation only. It is well suited for tracing concentration changes due to turbulence, less suited for cloud size tracing. A tight array of 8 sensors has been used to examine turbulently dispersed ions. High-resolution records are presented and discussed. The highest concentrations measured could be undiluted source material. The frequency distribution within a plume did not differ from that in a multitude of puffs. The distribution seems to be log-normal with a geometric standard deviation of about 2.45. The time resolution used corresponds to volume resolutions of 40, 225, and 650 cm³. Sample size had no apparent effect.     

THE MICRO-FEATURES OF HEAVY RAIN OVER GUANGZHOU IN FLOODS SEASON

In this paper, the raindrop spectral data collected at the Conghua station in Guangzhou area in June 1994 have been analyzed.It is found that the June rainfall causing great floods damage in southern China has the following features: It has long duration, large intensity, raindrop density and scale, with the largest raindrop diameter and rainfall intensity at 6.5 mm and 155.06 mm/hr respectively.on the other hand, according to weather system and rainfall nature, we divided the rainfall into five types and provided a group of Z-I relationships that can be referenced and used in radar quantitative measurement of rainfall.     

Uncoupled multi-layer model for the transfer of sensible and latent heat flux densities from vegetation

The sensible heat flux density C and the latent heat flux density E are coupled in the case of a multi-layer model of vegetation. Therefore two linearly independent combinations of C and E, the enthalpy flux density H and the saturation heat flux density J, are introduced. Two electrical analogues, for H and J, are designed. They are equivalent to the resistance scheme for C and E, but uncoupled. Penman's formulas for C and E, which are applicable only to single-layer models, can be expressed equivalently in terms of H and J. This version of Penman's formulas can be extended easily to multi-layer canopies.     

Oxygen Isotope Composition Of Human Teeth And The Record Of Climate Changes In France (Lorraine) During The Last 1700 Years

In order to study climate variations during the last 1700 years in eastern France, fifty-eight oxygen isotope compositions of phosphate were measured in human tooth enamel. The individuals, who lived in Lorraine, are assumed to have drunk local water derived directly from rainfall. According to previous work, drinking water is the main source of oxygen that sets the isotopic composition of phosphatic tissues in humans. The empirical fractionation equation determined from our data combined with those of Longinelli’s one [Geochim. Cosmochim. Acta 48 (1984) 385] was used to calculate the oxygen isotope composition of meteoric waters. The mean air temperature was inferred from these isotope ratios and the Von Grafenstein et al.’s [Geochim. Cosmochim. Acta 60 (1996) 4025] relationship between δ¹⁸O and air temperature. Oxygen isotope composition of present-day individuals yields a mean air temperature of 9.9± 1.7 ^∘C which is consistent with meteorological data. Application of this method to historical individuals results in mean air temperatures estimates 0 to 3 ^∘C higher than present-day air temperature. These warm air temperatures are not realistic during the so-called Little Ice Age for which an air-cooling of about 0.5 to 2 ^∘C has been documented. We propose that these relatively high δ¹⁸O values of human tooth enamel reflect higher mean δ¹⁸O values of meteoric water which can be attributed to an increased proportion of summer rainfall during the “Little Ice Age” time frame in Lorraine.     

Seasonal Variability of the Ion Composition,Phase State,and Mass Concentration of Aerosol in the Rural and Urban Atmosphere over Belgium (2001–2003)

Field data on the ion composition and mass concentration of aerosol in the rural (Wingene) and urban (Antwerp) regions of Belgium and the results of their thermodynamic analysis are presented. Ammonium nitrate and ammonium sulfate are found to be the major water-soluble components of aerosol particles. The seasonal variability of mass concentration, phase state, and ion composition of aerosol particles is largely determined by variations in temperature and relative humidity. It is shown that the content of ammonium nitrate and ammonium sulfate in PM2.5 is close to their thermodynamic equilibrium concentrations.