南京冬季持续性强浓雾天气中三级分档雾水的理化特性分析

2013年12月7—9日南京出现持续性强浓雾天气过程。利用观测试验中获取的三级分档雾水和分粒径气溶胶的水溶性离子浓度,气溶胶数浓度谱、雾滴谱以及自动气象站获取的气象要素等资料,通过对比研究浓雾过程中4—16 μm（3级）、16—22 μm（2级）、>22 μm（1级）3个粒径范围雾滴（雾水）与分粒径气溶胶的微物理特征和化学特性,探讨不同粒径气溶胶粒子吸湿增长对雾滴的贡献以及气溶胶离子组分对不同尺度雾滴化学性质的影响。结果表明,在强浓雾天气中,能见度为50 m左右,短波辐射减弱形成稳定逆温层,有助于污染气溶胶的累积并吸湿增长向雾滴转化。雾滴的增加主要集中在小滴范围, 直径在0.5—1 μm的气溶胶粒子对其贡献最大。各粒径段气溶胶中阴离子NO₃-和SO₄2-均表现出较高值,阳离子中Ca2+浓度最高。三档雾水中各阴、阳离子浓度均在4—16 μm小滴雾水中最高,16—22 μm中滴雾水和>22 μm大滴雾水的阴、阳离子浓度没有明显的高低之分。阳离子中Ca2+的浓度在第1级小滴雾水中最高,2级和3级雾水中NH₄+的浓度最高,阴离子中NO₃-和SO₄2-在各级雾水中浓度相差不大。雾水pH值2.7—6.9,呈酸性,小雾滴酸性更强。      

江苏省雾的集中程度及其气候趋势研究

引入雾的集中期和集中度的方法,对江苏省59个地面观测站1961—2007雾的发生频次资料进行了分析研究,得出了近47 a来江苏雾的时空分布特征及其相关统计结果。研究表明,集中度和集中期能够明显地分辨江苏省雾的时空分布非均匀特性。江苏省雾集中度呈现南北高、中间低的特点;集中期在47 a中出现较大波动。采用EOF方法分别对雾日数、集中度和集中期的距平值进行分析,其第一特征向量表现为同相位;其中雾日数的第一时间系数在1980s前后出现峰值,集中度和集中期距平值的第一时间系数表现为先减小后增大的总体趋势。通过气候趋势系数的计算表明苏北地区除4站点外均呈上升趋势。     

Exploring fog as a supplementary water source in Namibia

Namibia is an arid country where many rural and urban centres depend on ephemeral rivers for their water supply. These water sources are, however, limited and display seasonal salinisation. Fog occurs along the coast and extends for some distance inland, and it could be used as a source of drinking water. Data on groundwater salinisation and fog deposition were collected at villages of the indigenous communities and at the Gobabeb Training and Research Centre (GTRC) in the Central Namib Desert. Fog collection experiments were done with Standard Fog Collectors (SFCs) and 1-m² fog collectors made from the Raschel mesh that is used in SFCs from 1996 onwards. The results indicate that fog occurs throughout the year and that it has low major ion concentrations (chemical composition). The period of high fog deposition coincides with that of high groundwater salinity and would suit mixing of the two waters to provide water of good drinking quality to people in these areas. In conclusion, fog is a viable source of water in the Namib and could supplement traditional sources in rural settlements and perhaps also in urban water supply schemes in this region as in other parts of the world where it is used as a source of drinking water.

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The implementation of fog water collection systems in South Africa

Two fog water collection systems (FWCS) have been implemented in South Africa. Both are located in areas where communities experience acute water shortages but which are prone to frequent fog episodes. The first was located at a high elevation site at the Tshanowa Junior Primary (JP) School in the Soutpansberg located in the Northern Province and the other near a small rural community at Lepelfontein along the West Coast. The former represents a mountainous site, while the latter is located on a low level coastal plain. The principal aim of the projects was to implement operational FWCSs to supply the communities with water. During the period 1999 to 2001 the total recorded cloud water yields at the Tshanowa JP School and Lepelfontein water collection sites were in the region of 72 422 and 148 691 l, respectively. This is equivalent to just over 2 l m⁻² day⁻¹ at the Tshanowa JP School and 4.6 l m⁻² day⁻¹ at the Lepelfontein site. Despite the relatively low average daily yields recorded, the total water volume collected on a particular day may be considerable. In fact, at both sites the maximum daily yield exceeded 3800 l. Fog deposition accounted for around 25% and 88% of the total water yield measured at the Tshanowa JP School and Lepelfontein sites, respectively. Both experiments indicated that fog water collection holds considerable potential as an alternative water source in the mountainous regions and along the West Coast of South Africa.     

庐山2016年冬季三级分档雾水化学特征

探究不同尺度雾滴化学特征是深化雾微物理化学研究的重要内容。2016年12月—2017年1月在庐山开展雾综合观测实验,利用主动式三级分档雾水采集器（CASCC 3_stage）收集到3次雾过程73个分档雾水样本,雾滴分档粒径:4—16 μm（3级）,16—22 μm（2级）和≥22 μm（1级）。定量得到了分档雾水的pH、电导率（EC）及9种水溶性无机离子（Na+、NH₄+、K+、Mg2+、Ca2+、Cl-、NO₂-、NO₃-、SO₄2-）浓度（μeq/L）。结果表明,庐山冬季雾水酸化严重,pH为3.96—5.82,pH < 5.6的样品占98.6%且直径4—16 μm小雾滴的强酸性（pH < 4.5）样品最多,占比达54.2%,小雾滴酸性和电导率更强;NH₄+、Ca2+、NO₃-、SO₄2-是雾水的主要离子组分,[NH₄++Ca2++NO₃-+SO₄2-]分别在三级分档雾水中占总离子浓度（TIC）的83.8%、88.0%和88.7%;综合3次雾过程,总离子浓度、NH₄+、K+、NO₃-、SO₄2-在4—16 μm小雾滴存在富集,表现出尺度依赖特征;86%雾水样品[SO₄2-]/[NO₃-]介于0.5—3.0,属于硫酸和硝酸混合型酸化,雾水酸化主要原因是碱性缓冲物质与酸性组分不平衡以及可能存在有机酸贡献;同一观测点不同雾过程化学特征存在个例差异,第二次雾过程（12月25日14时—26日21时）（北京时）,总离子浓度、NH₄+、Ca2+、NO₃-、SO₄2-在16—22 μm尺度雾滴存在富集,这可能是雾区气溶胶浓度较低、降温、采样间隔和污染气体及气溶胶输送共同作用的结果。后向轨迹聚类和潜在源（PSCF）分析表明,观测期间影响庐山的气团均来自西部,来自湖南北部的局地气团占总轨迹数的68.99%,最为重要;PM_2.5、SO₂、NO₂具有相似潜在源区空间分布,主要位于湖北、湖南、安徽西南部和江西北部等邻近省份地区,以近距离输送为主。      

Pollutant concentrations in fog and low cloud water at selected sites of the Czech Republic

In this paper, the basic composition of fog and low cloud water are presented, resulting from the analyses of water samples from 111 fog/cloud events. The samples were collected at five sites located in various regions of the Czech Republic. Two sampling sites are in mountainous regions and three sites represent various urban areas. The mountain stations are located in two regions of the Czech Republic with different industry types. At all the sites, active fog collectors were employed. In the water samples, the conductivity, acidity (pH), cations (H⁺, Na⁺, K⁺, NH₄⁺, Mg²⁺, Ca²⁺) and anions (F⁻, Cl⁻, NO₃⁻, SO₄²⁻) were determined.A mean pH value of about 4.5 was obtained at mountain sites whereas the measurements in urban areas showed mean pH values from 4.9 to 6.4. The mean conductivity values in the samples from the two mountain stations were 137 and 191.5 μS cm⁻¹. The samples from urban sites showed mean values between 127.7 and 654.4 μS cm⁻¹. The maximum concentration means for the three dominant pollutants (expressed by the ratio mountain sites/urban sites) are 32.9/99.6 mg l⁻¹ for NO₃⁻, 32.5/192.9 mg l⁻¹ for SO₄²⁻ and 18.5/52.7 mg l⁻¹ for NH₄⁺. As expected, we found higher ion concentrations in the northern part of the Czech Republic where larger numbers of lignite-burning power plants, chemical factories and opencast lignite mines are located. A decrease in ion concentrations was observed at higher altitude sites, probably reflecting at least in part higher liquid water contents at these locations.     

Inversions,and fog,stratus and cumulus formation in warm air over cooler water

Two aspects of convection over oceans are discussed and the following conclusions are derived from theoretical considerations.

1. The air layer over the sea will usually convect even when the water surface is ten degrees or more colder than the initial air temperature.
2. An inversion at stratus cloud tops is created by the stratus, and is not a necessary preexisting condition. Such inversions persist after subsidence evaporates the cloud.
3. Radiation heat exchange does not play an essential role in stratus formation or maintenance, and can either heat or cool the cloud.
4. Dry air convection does not erode inversions at the top of the convecting layer. Examples of soundings are discussed.
5. Fogs are most likely to form at sea where the water is coolest, and need no radiation effects to initiate cooling, or a boost from patches of warmer water, to begin convection.
6. Both stratus cloud growth, and the evaporation of clouds by cloud top entrainment, readjust the vertical structure of the air to leave a constant wet-bulb potential temperature with height.

These conclusions are supported by, firstly, a convective model which has been developed and which shows that vapor-driven convection over the ocean will proceed with zero or negative heat fluxes, at rates which saturate the lowest layer of the atmosphere in a few hours to altitudes of many tens of meters. Secondly, the availability of condensed moisture at the top of the surface layer cools the warmer entrained overlying dry air parcels so that when they descend they are no warmer than the sea surface temperature, and this induces downward moving plumes. This occurs if the wet-bulb potential temperature of the overlying air is less than the sea surface temperature, even if it is ten degrees C, or more, warmer in actual temperature.     

近30a黔南地区辐射雾和雨雾时空分布特征

利用1991-2020年黔南地区12站逐日最小能见度、降水量、日照时数、云量、气温、相对湿度、风速等气象观测资料,对辐射雾和雨雾进行判定,采用正交函数分解（EOF）、Mann-Kendall突变检验、线性倾向估计等方法分析其时空分布特征。结果表明：黔南地区辐射雾和雨雾时空分布差异较大,辐射雾高发区为平塘、罗甸、龙里,雨雾为独山、都匀、长顺。都匀、龙里、长顺、瓮安、平塘、福泉、荔波、罗甸近10a辐射雾明显减少或雨雾异常增多,次区域特征显著;辐射雾日比雨雾日多42.2%,辐射雾占大雾过程87.1%,雨雾占13.9%,辐射雾主要在夏末至秋冬季,雨雾主要在冬季至初春;辐射雾2011年之后明显减少、雨雾2017年之后急剧陡升,均发生显著突变;辐射雾有9站呈减少趋势,雨雾有8站呈现增加趋势。     

Temporal characteristics and fog water collection during summer in Tenerife (Canary Islands, Spain)

The study of fog dynamics in the island of Tenerife began in 1993 at six sites. The analysis of the relationship between fog and several meteorological parameters was conducted at the site located at Anaga. Anaga is located at the summit of a mountain range, at an altitude of 842 m and 3.5 km away from the north-western coastline of the island. The study uses hourly data of the three summer months (June, July and August) that were collected over a period of nine years — from 1996 to 2005. The mean summer (June–August) rainfall was found to be 21.2 mm whilst the total volume of fog water collected was 879.9 l m^− 2; the daily average fog water collection was 9.5 l m^− 2 day^− 1, and the hourly average about 0.4 l m^− 2 h^− 1. Although these amounts were recorded with wind speeds of between 8 and 12 m s^− 1, the correlation between water collected and wind speed is not statistically significant. In spite of this, the volume of fog water collected and wind speed showed a very distinct daily behavioural pattern, their frequency and speed reaching their minimum at 12 a.m. and their maximum from 7 p.m. to 8 a.m. GMT. The importance of this research is that it shows that the fog in the Canary Islands occurs more frequently and makes a more significant contribution to the growth of vegetation in the summer (the dry season) than in the winter, when fog accompanies rainfall.     

江苏北部不同等级雾的微物理结构及个例分析

利用2015—2017年秋冬季在江苏北部观测到12次雾过程的雾滴谱数据及常规气象观测资料,统计分析了轻雾、大雾、浓雾、强浓雾和特强浓雾等级下的微物理特征量及雾滴谱分布,并通过一次雾过程的分析,探讨了不同雾等级下的主要微物理过程。结果表明:随着雾等级的提升,雾滴数浓度、含水量增长明显,而轻雾、大雾和浓雾的雾滴平均直径和最大直径差异不大,但当能见度小于200 m时,平均直径和最大直径显著增大;能见度下降时,平均数浓度谱和含水量谱的谱线上抬,从浓雾到强浓雾,粒径大于10 μm的大雾滴增长明显;雾滴数浓度主要由小雾滴控制,雾滴含水量受大雾滴影响;东海县郊平均的雾滴含水量与南京观测结果相差不大,但雾滴数浓度仅为南京的一半左右,平均直径大约是南京的2.3倍;个例分析中,能见度从1000 m下降到50 m,凝结核活化并凝结增长是主要微物理过程,但可凝结水汽是影响该过程效果的一个重要因子,可使雾滴数浓度和平均直径呈现不同的相关关系;能见度降到50 m以下时,碰并过程效果显著;日出后雾滴蒸发作用显现并逐步增强。      

Assessment of concentration of radionuclides in river water and bottom sediments

The results of modeling of ^{89, 90}Sr, ¹³⁷Cs, and ^{239, 240}Pu migration in the Techa River are compared with observed data. It is shown that taking into account of the process of mass exchange between the main stream of a river and underflow is important for adequate modeling of migration and accumulation of radiative substances in a river. It is difficult to obtain results of modeling corresponding to the observed data if the process is neglected. Taking into account the mass exchange is especially important in developing models for long enough rivers that were polluted by radionuclides during long time. Authors believe that, in future, the considered aspects of modeling radioactive substances in rivers can be generalized on chemical polluting substances with similar physical and chemical properties, for example, heavy metals, phenols, etc.     

陕西省雾的趋势变化特征研究

应用1961-2006年陕西省82个气象站逐月雾日资料.分析了全省雾目的年、季分布特点、长期变化趋势以及可能的影响因素.结果表明:陕西大雾及陕西全省大部分地区40多年的年雾日呈明显的减少趋势,减少最明显的地区主要位于陕北和关中北部及汉江盆地;除春季雾日减少较为明显外,其余各季均变化不明显;陕西年雾日变化与年平均气温的变化显著负相关,与年平均相对湿度的变化显著正相关;浓雾日变化趋势没有雾日显著.     

The spatial and temporal variability of fog and its relation to fog oases in the Atacama Desert, Chile

Fog has been studied in the Atacama Desert of Chile for the past ten years. This paper analyzes its temporal and spatial variability, relying in part on satellite images (GOES) to analyze the frequent orographic fog and the low cloud deck (stratocumulus, Sc) that generates advective fog in the area. Fog water fluxes were measured with Standard Fog Collectors (SFC). Field trips and observers provided information on cloud top and base and the presence of fog. Vegetation in fog oases were used to confirm the results of these surveys.The Sc moves onshore into the continent with different intensities depending on season and time of day. The maximum spatial extent occurs during winter and at night. Fog is frequent in the coastal cliffs, where fog water fluxes of 7.0 L m^− 2 day^− 1 were measured using a SFC. It is less frequent 12 km inland, where the collection rates were less than 1 L m^− 2 day^− 1. The height of the fog collector above the ground affected the collection rate. The highest fog water fluxes were recorded at Alto Patache at altitudes of between 750 and 850 m a.s.l. The growth or thickness of the cloud is important in the collection of fog water. The information that GOES provides on the altitude of the top of low clouds is used to analyze this factor. Fog oases are described and analyzed in relation to how the geographical location of fog influences the growth of vegetation.     

两种陆面方案对陆雾与海雾模拟效果的对比研究

利用WRF(Weather Research and Forecasting)模式,针对1次陆雾与1次同时包含近海雾区与开阔海域雾区的海雾个例,开展了2种陆面方案——SLAB(five-layer thermal diffusion scheme)方案与Noah(Noah land surface scheme)方案——的模拟效果对比研究。研究结果表明:1)SLAB方案与Noah方案在开阔海域雾区模拟中的表现基本一致,但只有前者成功再现了陆雾与近海雾区。2)对于陆雾,与SLAB方案相比,Noah方案在白天偏高的地表温度造成偏强的地面垂直热量通量,加之偏弱的垂直水汽通量共同使得地面相对湿度偏低20％,导致模拟失败。3)对于海雾,两种方案模拟的地表温度与地面垂直水汽通量之间的差异,直接导致了地面2 m气温与水汽混合比的差异,进而影响了渤海的地面低压天气系统的强弱与水汽平流的大小,从而使得它们对渤海近海雾区的模拟表现迥异。本次个例中,应用广泛且陆面过程完善的Noah方案对陆雾模拟的表现反而不如过程简单的SLAB方案,本文对此给出了初步的解释,但仍需进一步探究其原因。     

济南冬季雾微物理结构特征

2016年12月19日—2017年1月9日,受静稳天气影响,济南接连出现了10次大雾天气过程,期间最低能见度不足50 m。利用10次冬季雾过程收集的雾滴谱资料、自动气象观测站加密资料、NCEP/NCAR再分析资料以及常规气象资料,分析了济南冬季雾期间的环流背景、雾类型以及微物理结构特征等。结果表明：济南冬季雾中以小滴为主,直径8 μm以下的小滴占总数的88%以上,小滴数与数浓度具有较好的线性关系;谱型有“单峰窄谱”和“多峰宽谱”之分,“单峰窄谱”雾谱宽不超过13 μm,小雾滴所占比例很高,液态含水量与数浓度具有较好的线性关系,各微物理量较小,“多峰宽谱”雾平均谱宽在34 μm以上,液态含水量与直径12 μm以上的大滴数具有较好的线性关系,各微物理量较大;平流辐射雾的数浓度和液态含水量最大,辐射雾次之,蒸发雾最小;冬季雾具有明显的地域性特征,与南京和上海相比,济南冬季雾数浓度明显偏小;辐射雾和平流辐射雾中液态含水量偏小1～2个数量级,且谱宽明显偏窄。