Characteristic features of air ions at Mace Head on the west coast of Ireland

Coastal nucleation events and behavior of cluster ions were characterized through the measurements of air ion mobility distributions at the Mace Head research station on the west coast of Ireland in 2006. We measured concentrations of cluster ions and charged aerosol particles in the size range of 0.34–40 nm. These measurements allow us to characterize freshly nucleated charged particles with diameters smaller than 3 nm. The analysis shows that bursts of intermediate ions (1.6–7 nm) are a frequent phenomenon in the marine coastal environment. Intermediate ion concentrations were generally close to zero, but during some nucleation episodes the concentrations increased to several hundreds per cm³. Nucleation events occurred during most of the measurement days. We classified all days into one of seven classes according to the occurrence and type of new particle formation. Nucleation events were observed during 207 days in 2006, most prominently in the spring and summer months. Rain-induced events, in turn, were observed during 132 days. Particle formation and growth events mostly coincided with the presence of low tide. Also small cluster ions (0.34–1.6 nm) were characterized. Average concentrations of small ions were 440 cm^− 3 for the negative ions and 423 cm^− 3 for the positive ions. Average mean mobilities of small ions were 1.86 cm²V^− 1s^− 1 and 1.49 cm²V^− 1s^− 1 for the negative and positive polarities, respectively. Concentrations of small ions were observed to be strongly dependent on the variations of meteorological parameters including wind speed and direction.     

Seasonal variations of number size distributions and mass concentrations of atmospheric particles in Beijing

Particle number and mass concentrations were measured in Beijing during the winter and summer periods in 2003, together with some other parameters including black carbon (BC) and meteorological conditions. Particle mass concentrations exhibited low seasonality, and the ratio of PM2.5/PM10 in winter was higher than that in summer. Particle number size distribution (PSD) was characterized by four modes and exhibited low seasonality. BC was well correlated with the number and mass concentrations of accumulation and coarse particles, indicating these size particles are related to anthropogenic activities.Particle mass and number concentrations (except ultra-fine and nucleation particles) followed well the trends of 13C concentration for the majority of the day, indicating that most particles were associated with primary emissions. The diurnal number distributions of accumulation and coarse mode particles were characterized by two peaks.     

冰晶核化对雷暴云闪电行为影响的数值模拟研究

为了探讨冰晶核化对雷暴云闪电行为的影响,通过已有的三维对流云起、放电模式探讨对比了3种冰晶核化方案,分别为原模式中的经验公式YS方案及与气溶胶相关的DE方案和LP方案。研究表明冰晶核化方案对雷暴云内冰晶微物理发展特征、起电及放电过程均有一定影响。模拟结果显示:(1)考虑了气溶胶的两种新参数化方案中冰晶粒子在高温区(高于-13.8℃)出现,在雷暴云发展过程中DE方案和LP方案冰晶的垂直分布均大于YS方案。(2)DE方案和LP方案中高温区出现的冰晶所带电荷极性有明显的反转现象,导致雷暴云电荷结构产生差异;雷暴云发展旺盛时刻DE方案和LP方案出现三级性电荷结构,而YS方案在整个雷暴云过程都是偶极性,并且DE方案和LP方案中电荷空间分布区域更加广泛。(3)不同核化方案下雷暴云放电特征存在差异,YS方案在偶极性电荷结构背景下没有负地闪产生,而DE方案和LP方案中次正电荷区的存在促进了负地闪的发生,并且负先导出现在较低的高度范围内;DE方案和LP方案中电荷量级较大,因此云闪发生频次以及正、负先导传播次数增加明显。     

杭州灰霾天气超细颗粒浓度分布特征

2013年12月1—10日宁波市出现历史罕见持续性重度污染事件。基于常规天气观测、浙江省自动气象站、宁波慈溪边界层风廓线雷达和凉帽山岛370 m高塔、宁波市和舟山市污染物监测等资料,应用美国NOAA HYSPLIT4模式进行粒子后向轨迹分析,并将CALMET诊断模式应用到WRF中尺度数值模式输出,对本次污染发展和消散过程宁波市3 km以下气象要素进行精细化诊断分析,计算通风系数。结果表明：（1）合适的环流背景是污染发展和持续的主要原因。气溶胶粒子浓度升高过程中有3次弱冷空气影响,主要表现在800 m以上层次,为粒子的输送提供了好的动力条件,却又不影响边界层风速和稳定性。弱冷空气间歇期风力弱,风向快速变化,利于粒子的循环滞留。（2）污染发展和持续阶段宁波市区3000 m以下持续弱下沉气流,夜间边界层高度低,200 m以下存在明显逆温层,导致气溶胶粒子在低层的堆积和能见度的降低。（3）污染发展和持续阶段夜间通风系数均小于1 m²/s,扩散条件很差,而污染消散阶段通风系数明显增大。没有外源性粒子输入时,通风系数与气溶胶粒子浓度成负相关。     

On the formation and growth of atmospheric nanoparticles

In this paper we summarize recent experimental, theoretical and observational results on the formation and growth of atmospheric nanoparticles. During the last years significant progress has occurred to explain atmospheric nucleation and initial steps of the growth. Due to climatic and health effects of fine and ultrafine particles the formation and growth of new aerosol particles is of growing interest. The question “How and under which conditions does the formation of new atmospheric aerosol particles take place?” has exercised the minds of scientists since the time of John Aitken, who in the late 1880s built the first apparatus to measure the number of dust and fog particles. However, only during the last 15–20 years has the measurement technology developed to such a level that size distributions of nanometer-size particles and concentrations of gases participating in particle formation can be measured in the atmosphere. Also from a theoretical point of view atmospheric nucleation mechanisms have not been resolved: several mechanisms such as ion-induced (or ion mediated) nucleation, ternary and kinetic (barrier-less) nucleation have been suggested. In the most recent theory, the activation of existing neutral and/or ion clusters has been suggested.     

Relevance of ion-induced nucleation of sulfuric acid and water in the lower troposphere over the boreal forest at northern latitudes

The relevance of ion-induced nucleation of sulfuric acid and water (IINSW) in the troposphere over the boreal forest at northern latitudes is investigated by combining two existing and previously published models (MALTE — model to predict new aerosol formation in the lower troposphere; PARNUC — a parameterized steady-state model of neutral and ion-induced nucleation of sulfuric acid and water for atmospheric conditions). Simulations were performed for 4 days with observed new particle formation at ground level by using input data from the SMEAR II station in Hyytiälä, Finland. The selected days were chosen to cover a wide range of values of the parameters most relevant for IINSW. The results showed that ion-induced nucleation of sulfuric acid and water can contribute up to 15% to the total amount of newly formed particles in the size range of 3–10 nm inside the mixed layer at the Hyytiälä site. The importance of IINSW seemed to increase in the free troposphere above the boundary layer, however, lack of measurements in the vertical structure of the input parameters suggest that the model results are burdened with high uncertainties.     

On the distribution of physical and chemical particle properties in the atmospheric aerosol

Consideration of sources and growth dynamics of aerosols has led to the conclusion that there may be a distribution or variation of chemical composition and physical structure among atmospheric aerosol particles as a function of size, and within a narrow size range as well. A mathematical representation of these particle properties in terms of an additional dimension to the number size distribution is described. Examples of the relevance of this aspect of aerosol characterization for physical and chemical processes in the atmosphere are discussed. A review of the available techniques shows that several methods are available which can and have provided quantitative results on the distribution of particle properties. Examples of data from the literature have been selected and are presented as three-dimensional distributions illustrating the wide range of particle properties which may exist in narrow size intervals. An evaluation of these results reiterates the value of taking the distribution of particle properties in the atmosphere into account for sampling and modeling purposes.     

Forward Lagrangian stochastic simulation of a transient source in the atmospheric surface layer

We show that a forward Lagrangian stochastic (LS) model simulates well the ensemble-averaged concentration transient due to a short time (5 min) point source in the uniform atmospheric surface layer. In LS models, computational particles, which may not descend below ground level, are necessarily reflected at an imposed (artificial) boundary above ground. Model results were rather insensitive to the placing of the lower reflection boundary, and no definite benefit stemmed from including a parametrization for unresolved delays/displacements beneath the lower boundary.     

On the unified theory of atmospheric particle systems part ii: self–affine particles

As the second attempt at unifying treatment of atmospheric particle systems, this paper further examines shape characterization of atmospheric particles. First, to support the theoretical framework developed in Part I, methods for studying non-spherical particles are reviewed. It is argued that these different methods can be unified under fractal geometry through the generalized power laws given in Part I. Empirical power-laws for hydrometeors scat-tered in literature since 1935 are summarized and reevaluated in terms of fractals. Second, generalization from self-similar to self-affine particles is discussed. Self-affinity of atmospheric particles is exemplified by examining the exponents in the power laws between the length along a- and c-axis of ice crystals. It is argued that unlike Euclidean and self-similar particles, self-affine particles do not have a simple dimensional relation between original particles and their projections; the relation for projection of self-similar particles and Mandelbrot’ thumb rules for intersection respectively set the lower and upper bound. Using published data, self-affine particles are shown to exist in the at-mosphere. The existence of self-affine particles in turn calls for instruments that can simultaneously measure mass, area and maximum diameter (or their equivalents).     

Influence of the Saharan Air Layer on Atlantic Tropical Cyclone Formation during the Period 1--12 September 2003

Atmospheric Infrared Sounder (AIRS) data show that the Saharan air layer (SAL) is a dry, warm, and well-mixed layer between 950 and 500 hPa over the tropical Atlantic, extending westward from the African coast to the Caribbean Sea. The formations of both Hurricane Isabel and Tropical Depression 14 (TD14) were accompanied with outbreaks of SAL air during the period 1-12 September 2003, although TD14 failed to develop into a named tropical cyclone. The influence of the SAL on their formations is investigated by examining data from satellite observations and numerical simulations, in which AIRS data are incorporated into the MM5 model through the nudging technique. Analyses of the AIRS and simulation data suggest that the SAL may have played two roles in the formation of tropical cyclones during the period 1-12 September 2003. First, the outbreaks of SAL air on 3 and 8 September enhanced the transverse-vertical circulation with the rising motion along the southern edge of the SAL and the sinking motion inside the SAL, triggering the development of two tropical disturbances associated with Hurricane Isabel and TD14. Second, in addition to the reduced environmental humidity and enhanced static stability in the lower troposphere, the SAL dry air intruded into the inner region of these tropical disturbances as their cyclonic ?ows became strong. This effect may have slowed down the formation of Isabel and inhibited TD14 becoming a named tropical cyclone, while the enhanced vertical shear contributed little to tropical cyclone formation during this period. The 48-h trajectory calculations confirm that the parcels from the SAL can be transported into the inner region of an incipient tropical cyclone.     

Concentration profiles of particles settling in the neutral and stratified atmospheric boundary layer

An expression for the vertical equilibrium concentration profile of heavy particles, including the effects of canopy on the eddy diffusivity as well as corrections for atmospheric stability, is proposed. This expression is validated against measurements of vertical concentration profiles of corn pollen above a corn field. The fitted theoretical profiles show that particle settling is correctly accounted for. The sensitivity to variations in the turbulent Schmidt number, settling velocity and stability corrections are explicitly characterized. The importance of independent measurements of the surface flux of pollen in future experiments is noted.     

Influence of the Saharan Air Layer on Atlantic Tropical Cyclone Formation during the Period 1-12 September 2003

Atmospheric Infrared Sounder (AIRS) data show that the Saharan air layer (SAL) is a dry, warm, and well-mixed layer between 950 and 500 hPa over the tropical Atlantic, extending westward from the African coast to the Caribbean Sea. The formations of both Hurricane Isabel and Tropical Depression 14 (TD14) were accompanied with outbreaks of SAL air during the period 1-12 September 2003, although TD14 failed to develop into a named tropical cyclone. The influence of the SAL on their formations is investigated ...     

亚青会期间南京地区大气冰核的观测分析

2013年8月2—26日亚青会期间对南京地区进行了大气冰核的观测采样,同时结合气溶胶、气象要素等观测资料,研究了南京地区大气冰核浓度的分布特征,探究在污染管控措施下大气气溶胶的变化是否对冰核浓度产生影响。结果表明,大气气溶胶浓度在污染管控的措施下明显降低,冰核浓度在多种因素影响下没有明显降低的变化趋势,但有明显的日变化特征。燃放烟花的空气污染时刻,大气冰核浓度随污染物浓度的增加会明显增加。当活化湿度达到水面过饱和,温度范围为-12~-23℃时,南京夏季的冰核浓度范围为0.38~50.55 L~(-1)。将活化温度和冰面过饱和度同时加入到参数化公式中得到大气冰核浓度N(T,S_i)=0.003 1exp(-0.254 9T+0.161 6S_i)。进一步分析冰核浓度与PM_(2.5)、PM_(10)、PM_(10)-PM_(2.5)的关系,发现冰核浓度与PM_(10)-PM_(2.5)的相关性较高,相关系数为0.55,说明大粒径气溶胶粒子更容易充当冰核,大粒径气溶胶在冷云过程中起着更为重要的作用。     

Role of atmospheric ammonia in the formation of inorganic secondary particulate matter: A study at Kanpur,India

Levels of fine Particulate Matter (PM_fine), SO₂ and NO_x are interlinked through atmospheric reactions to a large extent. NO_x, NH₃, SO₂, temperature and humidity are the important atmospheric constituents/conditions governing formation of fine particulate sulfates and nitrates. To understand the formation of inorganic secondary particles (nitrates and sulfates) in the atmosphere, a study was undertaken in Kanpur, India. Specifically, the study was designed to measure the atmospheric levels of covering winter and summer seasons and day and night samplings to capture the diurnal variations. Results showed are found to be significantly high in winter season compared to the summer season. In winter, the molar ratio of to was found to be greater than 2:1. This higher molar ratio suggests that in addition to (NH₄)₂SO₄, NH₄NO₃ will be formed because of excess quantity of present. In summer, the molar ratio was less than 2:1 indicating deficit of to produce NH₄NO₃. The nitrogen conversion ratio (NO₂ to NO₃) was found to be nearly 50% in the study area that suggested quick conversion of NO₂ into nitric acid. As an overall conclusion, this study finds that NH₃ plays a vital role in the formation of fine inorganic secondary particles particularly so in winter months and there is a need to identify and assess sources of ammonia emissions in India.     

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采用欧拉方法分析盆地东北部夏季3例持续性暴雨过程的水汽输送及其异常特征,并利用拉格朗日轨迹模式模拟计算了影响川东北的主要水汽输送通道,结果表明：（1）不同纬度多系统相互作用对水汽输送的加强,是造成2007年和2010年两例持续性暴雨水汽强度异常大的重要原因。2012年持续性暴雨个例中异常水汽主要源于孟加拉湾和南海两支水汽的共同作用。（2）水汽源地可追溯至孟加拉湾、南海、西太平洋和阿拉伯海。边界层的水汽输送更多是自南海沿华南地区进入川东北;中低层水汽输送路径,或以孟加拉湾进入川东北,或以南海进入川东北,或两者共同作用。在垂直方向上,多条水汽输送通道的相互叠加,促使川东北产生强的水汽通量。（3）每条水汽输送通道在不同的个例中主次作用不一致。同一个例的水汽输送通道并非固定不变,不同降雨阶段可能与不同水汽输送通道对应。

     

Study of small ions concentration in the air above Athens, Greece

Measurements of positive and negative small atmospheric ion concentrations have been made regularly since 1968 at the National Observatory of Athens (NOA). In this paper the 17-year period 1968–1984 is summarized. The diurnal and annual variations are examined, and Fourier analysis is also used for the study of the diurnal variation. The concentrations of small ions follow a double diurnal course. The maxima occur near 3–5 h and 13–16 h local time (LT = GMT + 2 h). The minima are observed at 6–8 h and 21–23 h. The annual course of small ions presents maximum concentration values around the summer season. The mean of the small ion concentration (SIC) for the 17-year period (1968–1984) is n₊ = 188.8 ions/cm³ for positive ions and n₋ = 151.1 ions/cm³ for negative ions. Their ratio is equal to 1.25. The year-to-year variation of SIC for the examined period shows a negative trend. The results from multiple regression analysis show that wind speed and SIC are positively correlated, while relative humidity, smoke and sulphur dioxide are negatively correlated.     

春季黑潮延伸体海洋锋区经向位移与东亚大气环流的关系

采用高分辨率的海表温度资料定义了春季黑潮延伸体北侧海洋锋区的南北位置,并采用EOF分析、相关分析、合成分析、带通滤波等方法,探讨了其南北向位置变动与高空急流、风暴轴以及后期东亚降水之间的关系。结果表明,春季黑潮延伸体北侧海洋锋区位置的南北变动存在明显的年际、年代际变化,其与6月东亚高空急流、太平洋区域风暴轴的南北位置具有很好的对应关系。当春季黑潮延伸体海洋锋区偏北时,6月东亚高空急流、太平洋区域风暴轴偏北,反之亦然。进一步的研究还表明,春季黑潮延伸体海洋锋区经向位置的变动可通过影响东亚大气环流对6月东亚地区的降水产生影响,黑潮延伸体海洋锋区偏北(南)年,6月雨带有显著的北(南)移。     

春季青藏高原大气热源与长江中下游盛夏高温的关系

利用1961—2013年长江中下游地区盛夏(7—8月)日极端最高气温和NCEP/NCAR再分析逐日资料,分析了春季(4—5月)青藏高原大气热源特征,找到了影响长江中下游盛夏高温的热源关键区域,并就关键区大气热源对长江中下游盛夏高温的影响进行了诊断。结果表明:春季青藏高原主体中南部大气热源与长江中下游盛夏高温关系密切,当该区域大气热源偏弱(强),长江中下游盛夏高温日数偏多(少)的可能性大。当春季青藏高原关键区大气热源偏弱(强)时,春季南海到西太平洋暖池对流偏强(偏弱),南海上空为气旋性(反气旋性)异常环流,西太平洋副热带高压偏东(西),有利于南海夏季风爆发偏早(晚),往往有利于盛夏西太平洋副热带高压位置偏北(南),从而导致长江中下游盛夏高温日数偏多(偏少)。春季青藏高原关键区大气热源可以作为长江中下游盛夏高温的一个前期预报因子。     

两类厄尔尼诺事件发展年秋季印度洋海温异常特征对比

基于1951—2010年逐月海气多要素观测资料,对比分析了两类厄尔尼诺事件发展年秋季印度洋的海温异常及大气响应特征,探讨了印度洋偶极子的发生与两类厄尔尼诺事件特征的可能联系。结果表明,两类厄尔尼诺事件的发展年均会出现印度洋偶极子,但出现的概率不同:大多数东部型厄尔尼诺事件都会伴有正位相印度洋偶极子发生;而仅一半的中部型厄尔尼诺事件期间会出现正位相印度洋偶极子的异常海温型,且强度较弱。从印度洋偶极子与两类厄尔尼诺事件的物理联系上看,东部型厄尔尼诺事件期间,印度洋偶极子的发生与其强度联系密切:印度洋偶极子发生在东部型厄尔尼诺事件较强期间,两者通过海洋大陆的异常强下沉运动及大范围负异常降水相联系;东部型厄尔尼诺事件偏弱时并无印度洋偶极子出现,海洋大陆异常下沉运动及负异常降水很弱。然而,中部型厄尔尼诺事件期间印度洋偶极子的发生与其强度并无显著的关系,而与太平洋高海温区的位置存在一定的可能联系:在有印度洋偶极子发生的中部型厄尔尼诺事件发展年秋季,热带太平洋异常高海温区的位置相对偏东,海洋大陆出现显著下沉运动和大范围负异常降水,热带东印度洋为大范围强异常东风控制;但无印度洋偶极子发生的中部型厄尔尼诺事件时,热带太平洋高海温区位置相对偏西,极弱的海洋大陆下沉支对热带印度洋异常海温作用非常有限。     

Apposite of atmospheric electric parameters with the energy coupling function (ε) during geomagnetic storms at high latitude

In this paper we are concerned with the variation of the atmospheric electric field and the air–earth current due to the excessive power generated by the solar wind-magnetosphere dynamo during geomagnetic storms, recorded at Maitri in Antarctica during 2004. A major part of the power generated by the solar wind-magnetosphere dynamo is used in the formation of the ring current and the rest is utilized for Joule heating and auroral particle precipitation. The method adopted by Frank-Kamenetsky et al. [Frank-Kamenetsky A.V., Troshichev O.A., Burns G.B., Papitashvili V.O., 2001. Variations of atmospheric electric field in the near-pole region related to the interplanetary magnetic field. J. Geophys. Res. 106, A1, 179–190.] was utilized to delineate the variations due to the signatures of tropical thunderstorm activity from the geoelectric data; while statistical methods used in our earlier studies were used to delimit variation due to the constant buffeting of the solar wind. We find that the solar wind-magnetosphere energy coupling function (ε) to be well correlated with the atmospheric electric parameters during the onset of geomagnetic disturbances. However the correlation breaks down during minor storms and sub-storm events.