区域站和基准站气溶胶的分析

文章讨论了秋季（1994年10月）和冬季（1995年1月）在中国西部青海省共和县瓦里关山（36°17′N，100°54′E，海拔3816 m）基准站和中国东北黑龙江省五常县的龙凤山（44°44′N，127°36′E，海拔331 m）及中国东南沿海的浙江省临安县的横畈乡（30°18′N，119°44′E，海拔131 m）两个区域本底站（上述3站均属WMO）所采集的气溶胶样品的质量浓度、可溶性离子浓度的时空分布特征和变化规律。初步得出:气溶胶质量浓度和可溶性离子浓度以临安为最高。其次是龙凤山，而瓦里关山为最低     

The Effect of Weak Shear－induced Motion on Brownian Coagulation of Aerosol Particles

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国内外气溶胶观测网络发展进展及相关科学计划

气溶胶是气候变化研究中的一个极大的不确定性因素,国内外在此方面开展了大量的观测和科学研究。本文首先对当前全球两大气溶胶观测网络,世界气象组织(WMO)的全球大气观测计划(GAW)和气溶胶自动观测网(AERONET)的组织、规模、设备、数据和气溶胶网络的规范作了介绍,并对近年来国际上的重大气溶胶科学计划的目标、实验方法、步骤作了介绍,说明观测网络的重要性。在此基础上对中国气溶胶观测网络的地位做了分析,并指出其在正在开展的中国气溶胶科学研究中的重要性。     

Correlation of atmospheric visibility with chemical composition of Kaohsiung aerosols

The objective of this study was to investigate the correlation of visibility with chemical composition of Kaohsiung aerosols. Daytime visibility was observed around noon at two observation sites in metropolitan Kaohsiung, Taiwan in the years of 1999 and 2000. Both seasonal and diurnal variation patterns of visibility were observed in the region. Ambient aerosols were sampled and analyzed for 11 constituents, including water-soluble ionic species (Cl⁻, NO₃⁻, SO₄⁻², NH₄⁺, K⁺, Na⁺, Ca⁺², and Mg⁺²) and carbonaceous contents (OC, EC, and TC), to characterize the chemical composition of Kaohsiung aerosols. Furthermore, a stepwise multiple linear regression model was developed to elucidate the influence of aerosol species on visibility impairments. The results showed that sulfate was the dominant species that affected both light scattering coefficient and visibility. On average, the percentage contributions of visibility degrading species to light scattering coefficient were 29% for sulfate, 28% for nitrate, 22% for total carbon, and 21% for PM_2.5-remainder. An empirical regression model of visibility based on sulfate, nitrate, and relative humidity was also developed. The model showed that sulfate in PM_2.5 was the most sensitive species to visibility variation, suggesting that the reduction of sulfate in PM_2.5 could effectively improve the visibility of metropolitan Kaohsiung. During the investigation period, an event of Asian dusts intruded metropolitan Kaohsiung and dramatically increased the aerosol loadings, especially in the coarse particles. However, local visual air quality did not degrade accordingly during the Asian dust event because both visibility and light scattering coefficient are affected mainly by the fine particles. The results are discussed in detail in the paper.     

Cloud condensation nuclei measurements at Mace Head, Ireland, over the period 1994–2002

Analyses of cloud condensation nuclei (CCN) number concentrations (cm^− 3) measured at the Mace Head Atmospheric Research Station, near Carna, County Galway, Ireland, using a DH Associates Model M1 static thermal diffusion cloud chamber over the period from March 1994 to September 2002 are presented in this work. Air masses are defined as being ‘marine’ if they originate from a wind direction of 180–300° and ‘continental’ air masses are defined as originating from a wind direction of 45–135°. Air masses without such filtering were classified as ‘undefined’ air masses. Air masses were found to be dominated by marine sector air, re-affirming Mace Head as a baseline atmospheric research station. CCN levels for specific air masses at Mace Head were found to be comparable with earlier studies both at Mace Head and elsewhere. Monthly averaged clean marine (wind direction of 180–300° and black carbon absorption coefficient < 1.425 Mm^− 1) CCN and marine CCN varied between 15–247 cm^− 3 and 54–670 cm^− 3, respectively. As expected, significant increases in number concentration were found in continentally sourced CCN over that of marine CCN and were found to follow a log-normal distribution significantly tighter than that of clean marine air masses. No significant trend was found for CCN over the 9-year period. While polluted continental air masses showed a slight increase in CCN concentrations over the winter months, most likely due to increased fuel usage and a lower mixed boundary layer, the dominance of marine sector air arriving at Mace Head, which generally consists of background CCN concentrations, reduced seasonal differences for polluted air. Marine air showed a distinct seasonal pattern, with elevated values occurring over the spring and summer seasons. This is thought to be due to enhanced biogenic aerosol production as a result of phytoplankton bloom activity in the North Atlantic.     

机载激光雷达对青岛及周边海域的气溶胶探测

工作波长为532 nm的机载大气环境探测激光雷达AEDAL（Atmospheric Environment Detecting Airborne Lidar）装载在CMS_3807飞机上，于2005年11月7～11日期间在青岛地区及周边海域上空进行了飞行探测.此次实验的目的有两个：验证我国用于大气环境探测的激光雷达技术已经具备从地基向空基乃至天基发展的条件；获得青岛地区及周边海域边界层结构及大气气溶胶时空分布变化的特点.激光雷达的高时空分辨率为获取飞行路径上的边界层结构及气溶胶时空分布提供了可能.为了研究下垫面对边界层及气溶胶时空分布的影响，预定的飞行路径上包含了丰富的地形变化，有城市、丘陵、海区等.通过给出11月8日及11日的探测结果，不仅得到了不同地区边界层结构及气溶胶的时空分布特点，还可以看到冷锋、地形、地面气象场等因素对它们的影响.     

青藏高原平流层臭氧和气溶胶的变化趋势研究

通过分析SAGEⅡ资料,发现青藏高原平流层臭氧存在递减趋势,15—50 km臭氧的变化对臭氧总量变化贡献最大,其中25—50 km和15—25 km两层的贡献大致相当。通过青藏高原和中国东部地区平流层臭氧变化的对比,清楚地看出:两地臭氧总量变化的差异主要是由于在15—25 km臭氧变化不同所致。5—7月臭氧变化趋势的情况与年平均的变化类似,两地臭氧变化的差异主要在平流层低层,即15—25 km。青藏高原平流层气溶胶面密度的时间变化序列显示:大的火山喷发对青藏高原平流层气溶胶具有重要影响,其影响可持续6年左右。从1997年至今,青藏高原18—25 km气溶胶面密度增加,最大的增长出现在23 km,每年大约增长4%—5%。而在16—17 km气溶胶的面密度出现减少趋势。与此同时,在37 km以下,青藏高原的温度出现递减的趋势,而且其递减速度比中国东部地区快;在37—50 km,温度出现增加的趋势,青藏高原的增温也比中国东部地区快。青藏高原平流层低层气溶胶的增加和温度的降低都将增强该区域非均相反应的作用。     

复杂地形城市冬季边界层气溶胶扩散和分布模拟

着眼于城市冬季气溶胶扩散特征问题,针对地形复杂的兰州市及周边地区,开发了WRF模式,使之与包含了大气气溶胶辐射效应和气溶胶粒子扩散的综合大气边界层数值模式嵌套,以模拟城市冬季边界层气溶胶的扩散和分布规律。通过一个个例的模拟结果分析,揭示了兰州冬季气溶胶的扩散分布的如下特征;市区盆地内100 m以下存在东、西两个浓度高值中心,中心值为0.6~3.0 mg.m-3,往上浓度递减,1000 m高度处仅为0.02 mg.m-3。受排放源强、源高、气象场等因素的共同影响,白天盆地内气溶胶浓度随高度和时间的变化强烈,白天浓度随时间最大变化幅度为1.0 mg.m-3。气溶胶输送扩散高度可达到600~800 m,此高度以上浓度值很小。代表性测点上模拟的气溶胶浓度廓线表明,中午浓度达到最高,垂直扩散最强。这些结果与以往的烟雾层高度观测和气溶胶光学厚度观测结果吻合。夜间,盆地内气溶胶浓度随高度和时间的变化减弱,气溶胶输送扩散高度在400~500m,夜间浓度随时间变化平均幅度为0.05 mg.m-3。     

Micrometeorological Observations of a Microburst in Southern Finland

On the afternoon of 3 July 2004 in Hyytiälä (Juupajoki, Finland), convective cells produced a strong downburst causing forest damage. The SMEAR II field station, situated near the damage site, enabled a unique micrometeorological analysis of a microburst with differences above and inside the canopy. At the time of the event, a squall line associated with a cold front was crossing Hyytiälä with a reflectivity maximum in the middle of the squall line. A bow echo, rear-inflow notch, and probable mesovortex were observed in radar data. The bow echo moved west-north-west, and its apex travelled just north of Hyytiälä. The turbulence data were analysed at two locations above the forest canopy and at one location at sub-canopy. At 1412 EET (Eastern European Time, UTC+2), the horizontal and vertical wind speed increased and the wind veered, reflecting the arrival of a gust front. At the same time, the carbon dioxide concentration increased due to turbulent mixing, the temperature decreased due to cold air flow from aloft and aerosol particle concentration decreased due to rain scavenging. An increase in the number concentration of ultra-fine particles (< 10 nm) was detected, supporting the new particle formation either from cloud outflow or due to rain. Five minutes after the gust front (1417 EET), strong horizontal and downward vertical wind speed gusts occurred with maxima of 22 and 15 m s^?1, respectively, reflecting the microburst. The turbulence spectra before, during and after the event were consistent with traditional turbulence spectral theory.     

Recombination rates of small ions and their attachment to aerosol particles

It could be shown by measurements of the air conductivity and using a mean profile for the ionization rate that experimental and theoretical values of the recombination rate of small ions based on a three body recombination process (Thomson) are in very good agreement up to 20 km altitude. The divergency of the experimental and theoretical curves above 20 km can be interpreted by assuming that there exists in this altitude region a crossover from the three body recombination to a two body recombination process. The value of the recombination coefficient is about 4·10^–7 cm³ s^–1 in 25 km altitude, compared with 1.4·10^–6 cm³ s^–1 at ground level. Furtheron it was possible for the first time to get some experimental data of attachment coefficients up to 13 km from simultaneous measurements of the air conductivity and Aitken nuclei concentration. These values are in good agreement with those obtained by theoretical considerations.