全球闪电活动与对流层上部NO及O3的相关性分析

为了解闪电对对流层上部微量气体的贡献,利用全球水资源和气候中心(GHRC)提供的1995年4月—2006年6月的闪电卫星格点资料,以及高层大气研究卫星(UARS)上的卤素掩星试验(HALOE)1991年10月—2005年11月的观测资料,分析了全球闪电与对流层上部NO和O3体积分数的时空分布特征及其相关性。结果表明:全球闪电12、1、2月集中在南半球,6—8月集中在北半球,全球闪电的季节分布与NO、O3类似;NO体积分数在350 h Pa附近达到最大,该高度的南半球NO体积分数变化范围为7×10-12~11×10-12、北半球为3×10-12~17×10-12;450~300 h Pa,北半球夏季O3体积分数呈明显增加趋势,且同一高度上夏季的值比年平均值大25%左右,南半球夏季O3体积分数高于冬季,但差异并不大。结论进一步证明了闪电与对流层上部NO及O3的密切关系,也为研究全球气候变化提供有力证据。     

Global NOx Production by Lightning

Lightning is thought to represent an important source of tropospheric reactive nitrogen species NO_x (NO + NO₂),but estimates of global production of NO_x by lightning varyconsiderably. We evaluate the production of NO_x by lightning using a global chemical/transport model, satellite lightning observations, and airborne NO_x measurements. Various model calculations are conducted toassess the global NO_x production rate of lightning by comparing the model calculations with airborne measurements. The results show that the simulated NO_x in the tropical middle and upper troposphere are very sensitiveto the amount and altitude of the lightning NO_x used in the model. A global lightning NO_x production of 7 Tg N yr^–1uniformly distributed in convective clouds or 3.5 Tg N yr^–1 distributedin the upper cloud regions produces good agreement between calculated and measured NO_x concentrations in the tropics.     

Seasonal and global NOx production by lightning estimated from the Optical Transient Detector (OTD)

The Optical Transient Detector (OTD) lightning data for the 12‐month period of 1996 are used to estimate the seasonal and global distributions of lightning‐produced NO _x . The relatively small viewing footprint and the low detection efficiency of the OTD sensor and other difficulties require extrapolations of the OTD data to the actual global flash distributions. Furthermore, available measurements for the ratios of intracloud (IC) to cloud‐to‐ground (CG) flashes have been used to partition lightning counts for IC versus CG flashes from the OTD observations. The resulting lightning distributions are then used to calculate the global and seasonal production of NO _x , assuming a NO production rate of 6.2×10²⁵ molecules for each CG flash and 8.7×10²⁴ molecules for each IC flash. Consequently, we find that CG flashes produce more NO _x than IC flashes despite fewer CG flashes by a factor of 3 or more. NO _x production by lightning varies seasonally in accordance with the global lightning distribution, with the maximum production occurring in the Northern Hemisphere in the local summer. The latitudinal distribution of NO _x production exhibits a strong seasonal variation outside the tropics with the production occurring mainly in the summer hemisphere, whereas in the tropics the production is high throughout the year. The annual contribution to NO _x production by lightning is higher in the Northern Hemisphere than that in the Southern Hemisphere.     

Rainwater Chemistry and Wet Deposition over the Equatorial Forested Ecosystem of Zoétélé (Cameroon)

Within the framework of IDAF (IGAC DEBITS AFRICA: International GlobalAtmospheric Chemistry/DEposition of Biogeochemically Important TraceSpecies/Africa) network, data analysis is realised on precipitation chemical composition collected in Zoétélé, in Southern Cameroon. This station, located atabout 200 km from the Atlantic Ocean, is representative of a so-called `Evergreen Equatorial Forest' ecosystem. An automatic wet-only precipitation collector was operated at the station from 1996 to 2000. The rainfall regime, associated with eastward advection of moist and cool monsoon air masses, amounts to an average of 1700 mm/year. Inorganic and organic content of the precipitation were determined by IC in 234 rainfall events, representing a total 4,583 mm of rainfall from an overall of 7,100 mm.The mean annual precipitation chemistry and wet deposition fluxes characteristic of an African equatorial forest are quantified. Typical atmospheric gases and particles sources influence the precipitation chemical content and the associated deposition of chemical species. Indeed, hydrogen concentration is the highest (12.0 eq.L^–1) of the IDAF measurements, leading to acid rains with a low mean pH 4.92. The mineral species are dominated by nitrogenous compounds (NH₄ ⁺:10.5 and NO₃ ^–: 6.9 eq.L^–1), Ca²⁺ (8.9 eq.L^–1) and SO₄ ^{2 –} 5.1 eq.L^–1. Relationship between Ca^{2 +} and SO₄ ^{2 –} indicated aterrigeneous particulate source and an additional SO₄ ^{2 –} contributionprobably due to swamps and volcano emissions. Na⁺ and Cl^–concentrations, around 4.0 eq.L^–1, seem very low for this site,accounting for the marine source. Besides, strong correlations between NH₄ ⁺/K⁺/Cl^– indicate the biomass burning originof these species. Accordingly, precipitation chemistry in Zoétéléis influenced by three major sources: biogenic emissions from soil and forest ecosystems, biomass burning from savannah, and terrigenous signature from particles emissions of arid zones; and three minor sources: marine, volcano and anthropogenic. In spite of the relatively low concentration of all these elements, the wet deposition is quite significant due to the high precipitation levels, with for example a nitrogenous compounds deposition of 34 mmol.m^–2.yr^–1.     

Rainwater Chemistry and Wet Deposition over the Wet Savanna Ecosystem of Lamto (Côte d'Ivoire)

From the IGAC-DEBITS Africa network (IDAF), data sets on precipitation chemistry collected from the ‘wet savanna ecosystem’ site of Lamto (Côte d'Ivoire), are analyzed (1995–2002). Inorganic (Ca^{2 +}, Mg^{2 +}, Na⁺, K⁺, NH₄ ⁺, Cl^?, SO₄ ^{2 ?}, NO₃ ^?) and organic (HCOO^?, CH₃COO^?) ions content were determined using Ion Chromatography. The analyzed 631 rainfall events represent 8420.9 mm of rainfall from a 9631.1 mm total. The precipitation chemistry at Lamto is influenced by four main sources: natural biogenic emissions from savanna soils (NO _x and NH₃), biomass burning (savanna and domestic fires), terrigeneous particles emissions from dry savanna soils, and marine compounds embedded in the summer monsoon. The inter-annual variability of the weighted volume mean concentration of chemical species linked with wet deposition fluctuates by ～ 20% over the period. Ammonium concentration is found to be the highest (17.6 μ eq.l^{? 1}) from all IDAF sites belonging to the West Africa ecosystems. Ammonia sources are from domestic animals, fertilizers and biomass burning. In spite of the high potential acidity of 30.5 μ eq.l^{? 1} from NO₃ ^?, SO₄ ^{2 ?}, HCOO^? and CH₃COO^?, a relatively weak acidity is measured: 6.9 μ eq.l^{? 1}. The 40% acid neutralization is explained by the acid gas – alkaline soil particles interaction. The remaining neutralization is from inclusion of gaseous ammonia. When results from Lamto, are compared with those from Banizoumbou (dry savanna) and Zoetele (equatorial forest), a regional view for wet tropospheric chemistry processes is obtained. The high concentration of the particulate phase in precipitation emphasizes the importance of multiphases processes between gases and particles in the atmospheric chemistry of the West Africa ecosystems. For example, the nss Ca^{2 +} precipitation content, main indicator of terrigeneous particles, goes from 30.8 μ eq.l^{? 1} in dry savanna to 9.2 μ eq.l^{? 1} at Lamto and 8.9 μ eq.l^{? 1} in the Cameroon forest. A similar gradient is obtained for rainfall mineral particles precipitation content with contribution of 80% in dry savanna, 40% in wet savanna, and 20% in the equatorial forest.     

基于大气层结和雷暴演变的闪电和降水关系

选取2006—2008年发生在北京及其周边地区的28次雷暴过程,基于大气不稳定度参数和雷达参量对雷暴过程进行分类,分析了不同分类条件下的总闪电活动 (SAFIR3000三维闪电定位系统观测) 和对流降水 (雷达反演) 的关系。结果表明:整体而言,总闪对应降水量的平均值为1.92×107 kg·fl-1。依据对流有效位能和抬升指数对雷暴进行分类的分析表明,较强的不稳定状态对应了较小的总闪对应降水量,同时总闪频次和对流降水量的相关性更好。基于雷达特征参数的分类分析表明,总闪对应降水量在对流运动较弱情况下最小,其次是对流运动较强的情况下,而对流运动适中时最大。     

Precipitation Chemistry in the Sahelian Savanna of Niger, Africa

Within the framework of the IDAF (IGAC DEBITS AFRICA) network, we present in this paper data on precipitation and aerosol chemistry in the semiarid savanna of the Sahelian region of Niger. An automatic wet-only precipitation collector was operated at the Banizoumbou station during the entire 1996 rainy season (June to September 1996). Inorganic (Na⁺, NH ₄ ⁺ , K⁺, Mg²⁺, Ca²⁺, Cl^-, NO ₃ ^- , SO ₄ ^2- ) and organic contents of the precipitation (HCOOH, CH₃COOH, C₂H₅COOH) were determined by Ion Chromatography (IC) in 29 rainfall events. Once per week, bulk particle samples were collected on the same site, and soluble water material was determined by IC. We examined the influence of atmospheric gas and particle sources on the precipitation and aerosol chemical contents. We established the influence of marine, terrigenous, and biogenic sources in the Sahelian region. The terrigenous signature is dominant and related to Sahelian soil erosion, with a high calcium content in precipitation (31.2 eq L^-1) and in aerosols (1.8 g m^-3). Two other signatures of atmospheric sources are highlighted by the relatively high nitrogenous (ammonium and nitrate) and organic contents (formate, acetate) in the precipitation. Ammonium (12.9 eq L^-1) and nitrate (12.3 eq L^-1) contents confirm respectively the biogenic source of ammonia released by domestic animal excreta in Niger and the natural emissions from semiarid savannas soils, perturbed by wild or domestic animal grazing. In spite of a high potential acidity given by nitrate, formate and acetate; a weak acidity (H⁺ (2.1 eq L^-1) is calculated from the mean pH of 5.67 measured. A statistical analysis of the aerosol chemical composition clearly indicates that nitrates are strongly correlated at the 1% level with terrigenous ions, i.e., Ca²⁺ and Mg²⁺ (0.95 < r < 1). We observed a similar relationship between all the terrigenous ions and nitrate in the precipitation. In the Sahelian region, alkaline soil dust representative of the terrigenous contribution interact, with gaseous nitrogenous and carbonaceous compounds, leading to the neutralization of acid gases and subsequent weak acidity in precipitation. Finally, taking into account the main chemical characteristics of Banizoumbou precipitations and aerosols, which demonstrate the importance of heterogeneous and multiphase chemical processes, we propose a conceptual model of the atmospheric chemistry in the Sahelian region.     

Climatology of lightning activity in South China and its relationships to precipitation and convective available potential energy

This study examined lightning activity and its relationship to precipitation and convective available potential energy(CAPE) in South China during 2001–12, based on data from the Guangdong Lightning Location System, the Tropical Rainfall Measuring Mission satellite, and the ERA-Interim dataset. Two areas of high lightning density are identified: one over the Pearl River Delta, and the other to the north of Leizhou Peninsula. Large peak-current cloud-to-ground(LPCCG) lightning(75 kA) shows weaker land–offshore contrasts than total CG lightning, in which negative cloud-to-ground(NCG) lightning occurs more prominently than positive cloud-to-ground(PCG) lightning on land. While the frequency of total CG lightning shows a main peak in June and a second peak in August, the LPCCG lightning over land shows only a single peak in June.The ratio of positive LPCCG to total lightning is significantly greater during February–April than during other times of the year. Diurnally, CG lightning over land shows only one peak in the afternoon, whereas CG lightning offshore shows morning and afternoon peaks. The rain yield per flash is on the order of 10~7–10~8kg per flash across the analysis region, and its spatial distribution is opposite to that of lightning density. Our data show that lightning activity over land is more sensitive than that over offshore waters to CAPE. The relationships between lightning activity and both precipitation and CAPE are associated with convection activity in the analysis region.     

Emission of aliphatic amines from animal husbandry and their reactions: Potential source of N2O and HCN

We measured the emissions of volatile aliphatic amines and ammonia produced by the manure of beef cattle, dairy cows, swine, laying hens and horses in livestock buildings. The amine emissions consisted almost exclusively of the three methylamines and correlated with those of ammonia. The molar emission ratios of the methylamines to ammonia, and data on NH₃ emissions from animal husbandry in Europe, together with global statistics on domestic animals, were used to estimate the global emissions of amines. Annual global methylamine-N input to the atmosphere from animal husbandry in 1988 was 0.15±0.06 TgN (Tg=10¹² g). Almost 3/4 of these emissions consisted of trimethylamine-N. This represents about half of all methylamine emissions to the atmosphere. Other sources are marine coastal waters and biomass burning.Possible reaction pathways for atmospheric methylamines are shown. Among various speculative but possible products N₂O and HCN are of interest because the emission of methylamines could contribute to the global budgets of these compounds. Maximum atmospheric N₂O production from methylamines are below 0.4 Tg N/year, which is less than 10% of the annual N₂O growth rate. Although we do not expect the methylamine emissions to contribute in a major way to the atmospheric N₂O budget, more studies are needed to establish this conclusion beyond doubt. Similar conclusions hold for HCN.     

Relationship between Lightning Activity and Tropospheric Nitrogen Dioxide and the Estimation of Lightning-produced Nitrogen Oxides over China

To better understand the relationship between lightning activity and nitrogen oxides(NOX) in the troposphere and to estimate lightning-produced NOX(LNOX) production in China more precisely, spatial and temporal distributions of vertical column densities of tropospheric nitrogen dioxide(NO_2VCDs) and lightning activity were analyzed using satellite measurements. The results showed that the spatial distribution of lightning activity is greater in the east than in the west of China, as with NO_2 VCDs. However, the seasonal and annual variation between lightning and NO_2 density show different trends in the east and west. The central Tibetan Plateau is sparsely populated without modern industry, and NO_2 VCDs across the plateau are barely affected by anthropogenic sources. The plateau is an ideal area to study LNOX. By analyzing 15 years of satellite data from that region, it was found that lightning density is in strong agreement with annual, spatial and seasonal variations of NO_2 VCDs, with a correlation coefficient of 0.79 from the linear fit. Combining Beirle's method and the linear fit equation,LNOXproduction in the Chinese interior was determined to be 0.07(0.02–0.27) Tg N yr~(-1) for 1997–2012, within the range of 0.016–0.384 Tg N yr~(-1) from previous estimates.     

Sampling of Chemical Constituents in Electrically Active Convective Systems: Results and Cautions

On flights of a P3-B turboprop and a WB-57F jet aircraft within thunderstorm systems, short term spikes (1–2 sec or less in duration) in NO and O₃ were recorded and are attributed to hot or cold discharges occurring on the aircraft fuselage or air sampling inlets. One such spike of only ∼300 msec duration reached 325 ppbv of NO on the flight of the jet aircraft while at 13.8 km altitude. In a lightning flash to the P3-B aircraft, production of NO (expected) and NO₂ (unexpected) were directly observed. The NO production was ∼ 1.7 x 10²² molecules/m of flash length. In the P3-B flight at 5.5 km altitude and over a distance of ∼ 275 km within a highly electrically active thunderstorm complex in the equatorial central Pacific Ocean, there was no evidence of production of O₃ or CO by lightning flashes or by any type of hot or cold discharge involved in the development of free-air lightning flashes.     

Acidic deposition to forests: The 1985 chemistry of high elevation fog (CHEF) project

Abstract

The literature supporting significant water deposition directly from cloud and fog to the earth's surface is reviewed and previous aircraft and surface measurements of the acidity of this water are summarized. An overview of recent work on forest decline is given and an American (Mountain Cloud Chemistry Project) and Canadian (Chemistry of High Elevation Fog) program to look at the chemical deposition by clouds to high elevation forests, is‐described.

Preliminary measurements in late 1985 on two mountains in Quebec indicate that fog (cloud on the mountain) water pH values (≈3.8) near the summits (850–970 m) are much lower than precipitation pH values (≈ 4.3) at the same location; the summits are estimated to be in cloud 44% of the year with lower percentages at lower elevations; an estimate of total annual fog water deposition (77 cm) near the summit is similar to the average annual precipitation in Quebec; the estimated fog water hydrogen ion deposition (135 meq m^?2) is about three times that from the precipitation; the precipitation pH values may be lower (4.1 ver sus 4.3) at lower elevations with precipitation amounts perhaps 50% higher at higher elevations.     

Hydroxyl and Peroxy Radical Chemistry in a Rural Area of Central Pennsylvania: Observations and Model Comparisons

Atmospheric hydroxyl (OH), hydroperoxy (HO₂), total peroxy (HO₂ and organic peroxy radicals, RO₂) mixing ratios and OH reactivity (first order OH loss rate) were measured at a rural site in central Pennsylvania during May and June 2002. OH and HO₂ mixing ratios were measured with laser induced fluorescence (LIF); HO₂ + RO₂ mixing ratios were measured with chemical ionization mass spectrometry (CIMS). The daytime maximum mixing ratios were up to 0.6 parts per trillion by volume (pptv) for OH, 30 pptv for HO₂, and 45 pptv for HO₂ + RO₂. A parameterized RACM (Regional Atmospheric Chemistry Mechanism) box model was used to predict steady state OH, HO₂ and HO₂ + RO₂ concentrations by constraining the model to the measured OH reactivity and previously measured volatile organic compound (VOC) distributions. The averaged model calculations are generally in good agreement with the observations. For OH, the model matched the observations for day and night, with an average observed-to-modeled ratio of 0.80. In previous studies such as PROPHET98, nighttime NO was near 0 pptv and observed nighttime OH was significantly larger than modeled OH. In this study, nighttime observed and modeled OH agree to within measurement and model uncertainties because the main source of the nighttime OH was the reaction HO₂ + NO → OH + NO₂, with the NO being continually emitted from the surrounding fertilized corn field. The observed-to-modeled ratio for HO₂ is 1.0 on average, although daytime HO₂ is underpredicted by a factor of 1.2 and nighttime HO₂ is over-predicted by a factor of ∼2. The average measured and modeled HO₂ + RO₂ agree well during daytime, but the modeled value is about twice the measured value during nighttime. While measured HO₂ + RO₂ values agree with modeled values for NO mixing ratios less than a few parts per billion by volume (ppbv), it increases substantially above the expected value for NO greater than a few ppbv. This observation of the higher-than-expected HO₂ + RO₂ with the CIMS technique confirms the observed increase of HO₂ above expected values at higher NO mixing ratios in HO₂ measurements with the LIF technique. The maximum instantaneous O₃ production rate calculated from HO₂ and RO₂ reactions with NO was as high as 10–15 ppb h⁻¹ at midday; the total daily O₃ production varied from 13 to 113 ppbv d⁻¹ and was 48 ppbv d⁻¹ on average during this campaign.     

用远场辐射场反演云闪放电参数

用地面电磁场遥感闪电放电参数无论是在实际应用还是理论研究中都具有重要意义。文中基于电流传输线模式 ,提出了一种用单站远场VLF/LF辐射场反演云内放电参数的简便方法。当传输线电流从底部传播到顶部的时间只有几微秒时 ,整个传输线的VLF/LF辐射可以近似成偶极子辐射 ,即远场辐射场与电流的时间变化率和传输线长度的乘积成正比。因此 ,对远场辐射场做时间积分就能获得完整的电流矩波形 (上升沿有所加宽 ) ,而且传输线模式中的重要参数 ,电流从底部传播到顶端经历的时间 ,也可以近似地用辐射场时间积分幅度与辐射场幅度之比来估计。这一方法具有估计云闪双极性大脉冲辐射过程的放电参数的潜力。     

中国和日本降水化学特性的分析比较

本文对中国33个站、日本29个站及美国9个站的降水化学资料进行了分析比较.结果表明,中、日、美三国的降水化学特性有很大不同.三国都有酸雨,但以美国的pH平均值最低.雨水中离子总浓度以中国为最高,其中SO_4~=,NH_4~+和Ca~(++)的浓度特别高.日本雨水中Cl~-和Na~+的浓度很高.NO_3~-在美国雨水中最高.从雨水中离子结构组成和几种重要参量的比值分析表明,中国雨水中的离子浓度受陆地源影响很大,而影响日本雨水中离子浓度最大因素是海洋.在美国以工业交通污染的影响相对最大.文中还对中、日两国不同地区的降水化学特性进行了分析和讨论.     

Radar observations of precipitation production in thunderstorms

Abstract

Precipitation production is investigated for 9 intense thunderstorms that developed over the Lowveld in South Africa. A C‐band radar is used to observe the 3‐dimensional reflectivity pattern. Using an empirical relation between reflectivity factor and precipitation content and integrating over the storm volume provides an estimate of the total precipitation content aloft. Likewise, an area integration of the instantaneous rain rate at cloud base yields an estimate of the rate of total outflow. At their maturing stage, the storms had precipitation contents of 0.2 to 5.0 Tg and rainfall rates of about 0.3 to 2.0 Gg s^?1. The total accumulation of rain at the ground ranged from 1 to 10 Tg. The characteristic storm updraft, defined as the ratio of the area‐averaged rainfall rate to the volume‐averaged precipitation content, was about 5 ms^?1 for all storms. The time evolution of integral storm parameters is also presented and related to the overall storm development. The precipitation production values observed in the Lowveld storms compares well with previous estimates reported for large thunderstorms observed in Alberta and New England.     

中国地区闪电和对流层上部NOx的时空分布特征及其相关性分析

为了解闪电对对流层上部NO_x的贡献,本文利用美国全球水资源和气候中心（GHRC）提供的1995年4月~2005年12月的闪电卫星格点资料及高层大气研究卫星 (UARS) 上的卤素掩星试验装置 (HALOE) 1991年10 月~2005 年11月的观测资料,分析了中国地区闪电与对流层上部NO_x体积混合比的时空分布特征及两者的相关性.结果表明:中国地区闪电和对流层上部的NO_x在季节分布、年际分布和空间分布上保持很好的一致性,闪电是对流层上部NO_x的重要来源;NO极值高度在350 hPa左右,云闪直接产生的NO是极值产生的主要原因,NO₂的极值高度在250 hPa左右,因为闪电产生的NO在传输过程中会被氧化成NO₂并通过雷暴的垂直输送作用抬升到更高高度;强对流活动有利于NO_x的传输,而人类活动产生的NO_x一般较难输送到对流层上部,因此闪电多发区的NO_x极值较大,所在的高度也较高.     

雷州半岛盛夏闪电活动特征及其与降水的联系

利用雷州半岛2007年7、8月常规地面气象观测资料和闪电定位资料,分析了闪电活动与24 h降水量及雨强的关系,结果表明:雷州半岛盛夏地闪频数的最大值中心在其东侧海面上,地闪高发带沿海岸线呈南北向分布;地闪频次存在明显的日变化特征,13:00～18:00为闪电高发时段;无闪电时,有41.3%的降水事件24 h降水量≤1 mm,61.5%的降水事件雨强≤1 mm·h-1;有闪电时相应的事件概率分别为25.9%和37.7%;24 h降水量>30 mm的事件大多发生在有闪电的情况下,无闪电时极少发生;雨强概率分布的日变化特征不明显;有闪电活动时,雨强均值变化幅度加大.     

Major ionic composition of precipitation in the Nam Co region, Central Tibetan Plateau

A total of 48 precipitation samples have been collected from individual precipitation events at the Nam Co Monitoring and Research Station for Multisphere Interactions (Nam Co Station, 30°47′N, 90°58′E; 4730 m a.s.l) located in the central Tibetan Plateau from August 2005 to August 2006. All samples were analyzed for major cations (NH₄⁺, Na⁺, K⁺, Ca²⁺ and Mg²⁺) and anions (Cl⁻, NO₃⁻ and SO₄²⁻), conductivity and pH. Precipitation pH values ranged from 6.03 to 7.38 with an average value of 6.59. The high pH is due to large inputs of crustal aerosols in the atmosphere, which contain a large fraction of carbonate. Ca²⁺ is the dominant cation in precipitation with an average value of 65.58 μeq L^− 1 (4.91–301.41 μeq L^− 1), accounting for 54% of the total cations in precipitation. HCO₃⁻ is the predominant anion, accounting for 62% of the total anions. When compared with data from a snow pit in the Zhadang Glacier 50 km away (5800 m a.s.l), major ion concentration in precipitation at the Nam Co Station is much higher due to local aerosol inputs. Correlation and empirical orthogonal function (EOF) analysis indicate that regional crustal aerosols and species from combustion emissions of residents are the major sources for these ions, lake salt aerosols from the Nam Co nearby and regional mineral aerosols from dry lake sediments are secondary sources, and sea salt contribution is the least due to the long distance transport.     

On the wet removal of gaseous and particulate sulfur and nitrogen species from the atmosphere

The role of trace gases and aerosol particles in the control of sulfur and nitrogen levels in atmospheric precipitation is estimated on the basis of the enrichment factor in the precipitation of these elements relative to particulate matter in the air. By using air and precipitation chemistry data obtained at a Hungarian background air pollution station (K-puszta) it is found that the fraction of ammonium, nitrate and sulfate in precipitation, due to the removal of particulate matter is at least 59, 27 and 31%, respectively. The relationship between wet depositions and air concentrations of different species is determined statistically by applying daily data set. The regression equations obtained make the estimation of the sub-cloud scavenging ratios possible and they give some information on the magnitude of in-cloud scavenging processes. The results show that the in-cloud scavenging is a determining factor for precipitation sulfate, while it is relatively unimportant in the case of ammonium. The sub-cloud scavening of NO₂ and SO₂ is not too significant. However, for HNO₃, and NH₃ it is an effective process. The sub-cloud scavenging ratio of sulfur and nitrogen-containing particles varies around 0.25×10⁶.