Wet deposition of sulfate in the Inland Sea region of Japan

Precipitation chemistry data derived from a sampling network operated in the Inland Sea model region (June 1984–May 1985) are used as a basis for discussing the wet deposition of sulfate on a regional scale in Japan. Horizontal distribution, seasonal variation, relationship between wet deposition and precipitation amount, sulfate/nitrate ratio, and transport of sulfate from the ocean are discussed. Temporal trends in concentrations of atmospheric sulfur compounds and sulfate wet deposition in the model region are also covered.     

Wet deposition of ammonium in Europe

Ammonium concentration data in precipitation have been compiled to derive a concentration and deposition field for ammonium in Europe. Measurements referring to a total number of 218 measuring sites have been considered. Because of changes in the ammonium concentrations due to the use of improper sampling procedures, a correction procedure is proposed. This makes allowance for the type of sampler used, the length of the sampling period, and whether or not light-protected sample bottles are used. Dependent on the specific sampling procedure used correction factors range from 0.75 to 1.20. According to our calculations, the total wet deposition flux of ammonium in Europe in the early 1980s amounts to 2.4 Mt NH₄ ⁺y^-1. However, for some parts of Europe the flux cannot be estimated very reliably because of the low number or even the absence of measuring sites. Compared to earlier estimates for around 1960, the ammonium wet deposition flux has increased by approximately 25% during the period 1960–1980.     

7Be deposition in a high-rainfall area of New Zealand

Concentrations of natural ⁷Be in air and rainwater were monitored for one year at Hokitika, New Zealand. The mean airborne concentration was 3.1±1.3 mBq m^–3, the mean Hokitika, New Zealand. The mean airborne concentration was 3.1±1.3 mBq m^–3, the mean concentration in rainwater was 2600±1200 Bq m^–3, and the mean total deposition was estimated to be 130±99 Bq m^–2 wk^–1. Most of the ⁷Be was wet deposited and the washout ratio was independent of precipitation amount. A significant linear relationship exists between the weekly wet deposition flux and weekly precipitation at this high-rainfall site.     

Wet deposition of excess sulfate at Macquarie Island, 54° S

Annual wet deposition of excess sulfate at Macquarie Island has been estimated from 5 months of rainwater composition data covering the Austral summer of 1985/86. The resulting figure of 2.1±0.6 mmol/m²/yr is at the low end of previous estimates of maritime excess sulfate deposition by precipitation. Within estimated uncertainty limits this figure is consistent with the DMS emission flux which would be predicted for latitude 50°–60° S, based solely on available Northern Hemispheric DMS measurements.Temporarily at the International Meteorological Institute, Stockholm University, S-106 91, Stockholm, Sweden.     

Precipitation Chemistry and Wet Deposition in Kruger National Park, South Africa

The chemical composition, as well as the sources contributing to rainwater chemistry have been determined at Skukuza, in the Kruger National Park, South Africa. Major inorganic and organic ions were determined in 93 rainwater samples collected using an automated wet-only sampler from July 1999 to June 2002. The results indicate that the rain is acidic and the averaged precipitation pH was 4.72. This acidity results from a mixture of mineral acids (82%, of which 50% is H₂SO₄) and organic acids (18%). Most of the H₂SO₄ component can be attributed to the emissions of sulphur dioxide from the industrial region on the Highveld. The wet deposition of S and N is 5.9 kgS⋅ha⁻¹⋅yr⁻¹ and 2.8 kgN⋅ha⁻¹⋅yr⁻¹, respectively. The N deposition was mainly in the form of NH₄ ⁺. Terrigenous, sea salt component, nitrogenous and anthropogenic pollutants have been identified as potential sources of chemical components in rainwater. The results are compared to observations from other African regions.     

Determination of Sulfur Balance Between the Atmosphere and a Norway Spruce Forest Ecosystem: Comparison of Gradient Dry + Wet and Throughfall Deposition Measurements

Total sulfur deposition was determined above a Norway spruce forest, in Hungary. Two methods were applied, on one hand dry + wet deposition measurements and on the other, throughfall and stemflow deposition estimations have been carried out. Results show: total depositions are 3.3 and 3.2 g S m^–2 yr^–1 determined by dry + wet and throughfall deposition methods, respectively. The share of the dry deposition in the total S-load is 73%. The agreement between the results of the two different methods is good and suggests the needlessness of complicated dry + wet flux measurements, i.e. the total and dry deposition of sulfur compounds to forests can be determined by simple throughfall and wet deposition measurements.     

Estimation of fog deposition on epiphytic bryophytes in a subtropical montane forest ecosystem in northeastern Taiwan

The fog meteorology, fog chemistry and fog deposition on epiphytic bryophytes were investigated from July 2000 to June 2001 in the Yuanyang Lake forest ecosystem. The elevation of the site ranges from 1650 to 2420 m, at which the high frequency of fog occurrence throughout the year has been thought to be of benefit to the establishment of the primary Taiwan yellow cypress forest [Chamaecyparis obtusa var. formosana (Hayata) Rehder] and to the extensive growth of the epiphytic bryophytes. A weather station including a visibility sensor and an active fog collector was installed for fog meteorological and chemical study. The fog deposition rate on epiphytic bryophytes was estimated by measuring the increase rate in plant weight when exposed to fog. Average fog duration of 4.7 and 11.0 h per day was measured in summer months (June to August) and the rest of the year, respectively. November 2000 was the foggiest month in which the average fog duration reached 14.9 h per day. The ionic composition of fog water revealed that the area was less polluted than expected from literature data. The in situ exposure experiments done with the dominant epiphytic bryophytes showed an average fog deposition rate of 0.63 g H₂O g⁻¹ d. w. h⁻¹, which approximated 0.17 mm h⁻¹ at the stand scale. The nutrient fluxes estimated for February 2001 showed that for all ions, more than 50% of the ecosystem input was through fog deposition. These results demonstrate the importance of epiphytic bryophytes and fog deposition in nutrient cycling of this subtropical montane forest ecosystem. The incorporation of fog study in the long-term ecosystem research projects is necessary in this area.     

Aerosol characteristics during winter fog at Agra,North India

Simultaneous measurements on physical, chemical and optical properties of aerosols over a tropical semi-arid location, Agra in north India, were undertaken during December 2004. The average concentration of total suspended particulates (TSP) increased by about 1.4 times during intense foggy/hazy days. Concentrations of SO₄ ²⁻, NO₃ ⁻, NH₄ ⁺ and Black Carbon (BC) aerosols increased by 4, 2, 3.5 and 1.7 times, respectively during that period. Aerosols were acidic during intense foggy/hazy days but the fog water showed alkaline nature, mainly due to the neutralizing capacity of NH₄ aerosols. Trajectory analyses showed that air masses were predominantly from NW direction, which might be responsible for transport of BC from distant and surrounding local sources. Diurnal variation of BC on all days showed a morning and an evening peak that were related to domestic cooking and vehicular emissions, apart from boundary layer changes. OPAC (Optical properties of aerosols and clouds) model was used to compute the optical properties of aerosols. Both OPAC-derived and observed aerosol optical depth (AOD) values showed spectral variation with high loadings in the short wavelengths (<1 μm). AOD value at 0.5 μm wavelength was significantly high during intense foggy/hazy days (1.22) than during clear sky or less foggy/hazy days (0.63). OPAC-derived Single scattering albedo (SSA) was 0.84 during the observational period, indicating significant contribution of absorbing aerosols. However, the BC mass fraction to TSP increased by only 1% during intense foggy/hazy days and thereby did not show any impact on SSA during that period. A large increase was observed in the shortwave (SW) atmospheric (ATM) forcing during intense foggy/hazy days (+75.8 W/m²) than that during clear sky or less foggy/hazy days (+38 W/m²), mainly due to increase in absorbing aerosols. Whereas SW forcing at surface (SUF) increased from −40 W/m² during clear sky or less foggy/hazy days to −76 W/m² during intense foggy/hazy days, mainly due to the scattering aerosols like SO₄ ^2-.     

Atmospheric deposition of nitrogen, sulfur and chloride in Thessaloniki, Greece

In the present study, the wet and dry depositions of particulate NO₃⁻, SO₄²⁻, Cl⁻ and NH₄⁺ were measured using a wet/dry sampler as a surrogate surface. Gas phase compounds of nitrogen, sulfur and chloride (HNO₃, NH₃, SO₂ and HCl) were measured by an annular denuder system (ADS) equipped with a back up filter for the collection of particles with diameter ≤ 5 μm. Ambient concentrations of NO, NO₂ and SO₂ were also taken into consideration. Sampling was conducted at an urban site in the center of the city of Thessaloniki, northern Greece. The presence of the aerosol species was examined by cold/warm period and the possible compounds in dry deposits were also considered. Dry deposition fluxes were found to be well correlated with ambient particle concentrations in order to be used for the calculation of particle deposition velocity. Average particulate deposition velocities calculated were 0.36, 0.20, 0.20 and 0.10 cm s^− 1 for Cl⁻, NO₃⁻, SO₄²⁻ and NH₄⁺, respectively. Total dry deposition fluxes (gas and particles) were estimated at 3.24 kg ha^− 1 year^− 1 for chloride (HCl + p-Cl), 9.97 kg ha^− 1 year^− 1 for nitrogen oxidized (NO + NO₂ + HNO₃ + p-NO₃), 5.32 kg ha^− 1 year^− 1 for nitrogen reduced (NH₃ + p-NH₄) and 15.77 kg ha^− 1 year^− 1 for sulfur (SO₂ + p-SO₄). 70–90% total dry deposition was due to gaseous species deposition. The contribution of dry deposition to the total (wet + dry) was at the level of 60–70% for sulfur and nitrogen (oxidized and reduced), whereas dry chloride deposition contributed 35% to the total. The dry-to-wet deposition ratio of all the studied species was found to be significantly associated with the precipitation amount, with nitrogen species being better and higher correlated. Wet, dry and total depositions measured in Thessaloniki, were compared with other countries of Europe, US and Asia.     

近46年青藏高原干湿气候区动态变化研究

利用青藏高原62个气象站1961～2006年逐日气象资料, 用世界粮农组织 (FAO) 在1998年推荐的、并唯一承认的Penman-Menteith模式计算潜在蒸散量; 比较了降水量、积温降水比、气温降水比、蒸散降水比和降水蒸散比5种湿润度指标在青藏高原的适用性, 用常规统计方法和墨西哥帽小波变换分析青藏高原各气候区干湿状况及其界线的动态变化。结果表明: 5种指标中, 用降水蒸散比得到的青藏高原湿润、半湿润、半干旱、干旱和极端干旱气候区的分区结果比较合理; 近46年来青藏高原大部分地区湿润度和每个气候区的平均湿润度均呈增加趋势, 半干旱和半湿润气候区的界线呈向西北推进趋势, 气候在向暖湿方向发展。     

Chemical characterization of wet precipitation events and deposition of pollutants in coal mining region,India

The present study investigated the chemical composition of wet atmospheric precipitation in India’s richest coal mining belt. Total 418 samples were collected on event basis at six sites from July to October in 2003 and May to October in 2004 and analysed for pH, EC, F⁻, Cl⁻, , , Ca²⁺, Mg²⁺, Na⁺, K⁺ and . The average pH value (5.7) of the rainwater of the investigated area is alkaline in nature. However, the temporal pH variation showed the alkaline nature during the early phase of monsoonal rainfall but it trends towards acidic during the late and high rainfall periods. The rainwater chemistry of the region showed high contribution of Ca²⁺ (47%) and (21%) in cations and (55%) and Cl⁻ (23%) in anionic abundance. The high non seas salt fraction (nss) of Ca²⁺ (99%) and Mg²⁺ (96%) suggests crustal source of the ions, while the high nss (96%) and high ratio signifying the impact of anthropogenic sources and the source of the acidity. The ratio of varies from 0.03 to 3.23 with the average value of 0.84 suggesting that Ca²⁺ and play a major role in neutralization processes. The assessment of the wet ionic deposition rates shows no any specific trend, however Ca²⁺ deposition rate was highest followed by and _.     

基于旋翼无人机观测的雾天和霾天VOCs垂直分布特征研究

为研究雾和霾天气下VOCs时空变化特征,于2020年11月19日—2021年1月15日在江苏省东海国家气象观测站进行为期58 d的外场观测试验。利用自主研发的多旋翼无人机捕获2次辐射雾和2次霾天气过程,获得气温、气压、相对湿度、风向、风速、VOCs、O₃等7种要素100多条垂直廓线。结果表明：时间上,霾过程夜间VOCs体积浓度(0.225～0.253 ppm(parts per million, 1 ppm=10^-6))明显高于白天(0.191～0.205 ppm),雾形成前体积浓度(0.121～0.239 ppm)显著高于雾过程(0.056～0.209 ppm)。雾过程中VOCs体积浓度与雾强度变化相反,雾层高度与VOCs体积浓度剧烈变化高度一致,雾层(<200 m)中VOCs体积浓度(0.172～0.178 ppm)明显减小,显著低于雾形成前(0.195～0.240 ppm),雾层以上浓度变化大,雾结束后1 h内保持雾过程中分布特点。雾对逆温层中的水溶性污染物有清除作用,VOCs体积浓度和O₃质量浓度均下降。     

云辐射效应在华北持续性大雾维持和发展中的作用

观测研究发现华北地区的持续性大雾天气通常伴随高层云的存在,具有云-雾共存结构特征,为揭示云在持续性大雾维持和发展中的作用,利用中尺度数值模式WRF,结合华北雾霾观测试验期间的卫星、探空、地面观测、系留气艇、微波辐射计等观测资料,研究了2011年12月3—6日和2013年1月28—31日两次华北持续性大雾天气形成和发展演变过程。在模拟与观测对比检验研究的基础上,重点开展了云辐射效应在大雾维持和发展中作用的探讨。研究结果表明:两次大雾过程持续时间超过48 h,近地面具有偏南暖湿平流,在持续性大雾发展过程中,均出现了由单层雾发展为云-雾共存结构,一般是雾形成24 h以后有中高云移到雾层之上,云底高度在3 km以上,云厚超过3.5 km,云中以冰晶和雪晶为主。白天云-雾共存结构出现后,云-雾的反照率效应使地表接收的短波辐射减少71%—84%,地面增温效应显著减小,从而阻碍了大雾的消散过程,使大雾天气得以维持,同时由于云-雾产生的温室效应,湍流过程加强,使地面雾向上扩展,雾在稳定层内维持;夜晚云-雾共存时,由于云-雾温室效应使地表净长波辐射增大超过70 W/m2,导致地面长波辐射冷却过程减弱,并不利于雾的加强,但云对雾的增温效应有利于混合层内的湍流扩散过程,促使雾在更高的空间内得以维持。可见,在云-雾共存结构中,云辐射效应有利于低层大雾的长时间维持,对持续性大雾的形成和发展产生了重要作用。      

基于FY-3B卫星资料的中国南海海区1—3月海雾时空分布特征研究

为全面了解中国南海海区海雾的分布特征,为南海海雾气象服务提供基础背景资料,利用2011—2016年1—3月FY-3B气象卫星资料的雾监测产品,分析了中国南海海区海雾的时空分布特征。结果表明：中国南海海雾具有特定的区域特征,中国南海海雾多出现在华南沿海、北部湾沿海、琼州海峡和海南岛东北部沿海海区,南海南部海域出现海雾概率低;南海出现高频次海雾的时间多发生在2月,1月次之,3月最少。该研究结果可为中国南海海雾研究提供背景资料。     

长江中上游冬季山地雾边界层特征及生消过程分析

利用2010年12月在湖北宣恩观测山地雾获得的边界层廓线、雾滴谱、能见度资料,分析了该地雾过程的边界层特征及其生消过程。结果表明:1)宣恩山地雾主要由夜间辐射冷却引起,且能见度多在200 m以上;垂直发展深厚,成熟时厚度达到400~600 m。2)夜间风场主要由山风环流控制,风向多为东南风;入夜及雾生前期,地面风速不超过0.5 m/s,雾消前增大至2.0 m/s左右。3)雾生前观测到"C"字型温度层结,中下层气温降温率在0.3~1.0℃/(100 m)之间;结合该时段近地层露点温度逆温,离地200 m左右率先饱和成云;雾消时低空相对湿度依然保持较大值,重新变为空中雾层。4)雾前1~2 h地面及植被表明温度显著上升,个别升温率达1℃/h,对应时段地面相对湿度达到饱和,与其他地区有明显区别,对预报宣恩山地雾有积极意义。     

Sulfur dioxide in rain clouds: Gas-liquid scavenging efficiencies and wet deposition rates in the presence of formaldehyde

The interaction of formaldehyde with SO₂ dissolved in the aqueous phase of clouds leads to the formation of hydroxymethane sulfonate. The impact of this process upon the gas-liquid equilibrium distribution of SO₂ in rain clouds and the ensuing wet SO₂ precipitation rate is explored. Model vertical SO₂ distributions are derived from observational data for three atmospheric regions: continental polluted, continental remote, and marine. The wet deposition rate for SO₂ in the polluted atmosphere increases by about a factor of two in the presence of formaldehyde compared with its absence. The effect is much stronger in the remote atmosphere leading to a potentially significant enhancement of wet SO₂ deposition. In the marine atmosphere, wet deposition of SO₂ may contribute as much as 35% to the total removal rate for SO₂ by all processes including dry deposition and chemical conversion to sulfate.     

Soluble organic compounds in fog and cloud droplets: what have we learned over the past few years?

We have recently set up a new procedure for characterising the water soluble organic compounds (WSOC) in fog water, for which information is still rather limited. Fog samples collected during the 1998–1999 fall–winter season in the Po Valley (Italy) were analysed following this procedure, which allows a quantitative determination of three main classes of organic compounds (neutral species, mono- and di-carboxylic acids, polycarboxylic acids), together accounting for ca. 85% of the total WSOC. This procedure also provides information on the main chemical characteristics of these three classes of compounds (functional groups, aliphatic vs. aromatic character, etc.). The enhanced chemical knowledge on fog/cloud chemical composition opens new scenarios as far as chemical and microphysical processes in clouds and fogs are concerned.     

北美和欧亚大陆冬季快速增温与地表干湿变化

采用东英吉利大学气候研究中心（CRU）提供的月地表温度和降水资料,分析了全球年平均及冬季地表温度变化趋势,发现在北半球中高纬地区半干旱区冬季快速增温。在此基础上通过分析帕默尔干旱指数（PDSI）研究了北美和欧亚大陆冬季地表干湿变化的时空特征和差异,并讨论北美和欧亚大陆冬季快速增温对地表干湿变化的影响。结果表明,北美大陆南部微弱变湿,加拿大北极群岛变湿明显,而在北美大陆的中西部有明显的变干趋势;欧亚大陆大部分地区在冬季有一定的变干趋势,其中尤以西欧南部,中国华北、东北,蒙古中北、东北部及俄罗斯远东地区变干最为显著。但北美和欧亚大陆1950-2008年冬季降水并无显著变化趋势,地表干湿变化主要受气温的影响,尤其是在冬季增温最为快速的地区。     

Chemistry of Precipitation Events and Inter-Relationship with Ambient Aerosols over a Semi-Arid Region in Western India

The precipitation events (n = 91), collected for 3 years (2000–2002) during the period of SW-monsoon (Jun–Aug) from an urban site (Ahmedabad, 23.0°N, 72.6°E) of a semi-arid region in western India, are found to exhibit characteristic differences in terms of their solute contents. The low solute (<700 μeq L⁻¹) events are either marked by heavy precipitation amount or successive events collected during an extended rain spell; whereas light precipitation events occurring after antecedent dry period are characterized by high solutes (>700 μeq L⁻¹). The ionic composition of low solute events show large variability due to varying contribution of anthropogenic species (: 1%–74%; : 1%–25%; and : 8%–68%) to the respective ion balance. In high solute events, ionic abundances are dominated by mineral dust (Ca²⁺ and ) and sea-salts (Na⁺ and Cl⁻). These differences are also reflected in the pH of low solute events (range: 5.2–7.4, VWM: 6.4) and high solute events (range: 6.6–8.2, VWM: 7.3). The comparison of Ca²⁺/Na⁺ and nss- ratios (on equivalent basis) in rain and aerosols suggests that the ionic composition of high solute events is influenced by below-cloud scavenging; whereas evidence for in-cloud scavenging is significantly reflected in low solute events. The annual wet-deposition fluxes of and are 330 and 480 mg m⁻² y⁻¹, respectively, in contrast to their corresponding dry-deposition fluxes (14 and 160 mg m⁻² y⁻¹); whereas wet and dry removal of Ca²⁺, Mg²⁺ and are comparable.     

黄河源区干湿演变条件下的水汽输送特征研究

基于"黄河源区玛曲-若尔盖土壤温湿监测网络"自2008年观测以来至2017年的观测资料,通过分析多层土壤湿度异常百分比指数SMAPI(Soil Moisture Anomaly Percentage Index),捕捉10年来该地区的干湿演变过程,并利用再分析数据资料NECP FNL(National Centers ...