EVOLUTION OF LIQUID WATER CONTENT IN A SEA FOG CONTROLLED BY A HIGH-PRESSURE PATTERN

On March 16–17, 2008, a sea fog occurred in Dianbai in the west of Guangdong Province and was accompanied by a high-pressure synoptic system. Using comprehensive observation datasets, this study analyzes the evolution of liquid water content during this sea fog and investigates the relationships between liquid water content and the average diameters and count densities of fog droplets, air temperature, wind speed and turbulence exchanges. The main results are presented as follows. (1) The sea fog showed a quasi-periodic oscillation characteristic, i.e., it developed, disappeared and then developed again. (2) During the sea fog, the number of fog droplets changed significantly while the changes in average diameter of the fog droplets were relatively small. The development and disappearance of the sea fog correlated significantly with the fog droplet numbers. (3) The air-cooling mechanism played a significant role in sea fog formation and development. However, the influences of this mechanism were not evident during fog persistence. (4) During sea fog formation, weak turbulence exchanges were helpful for fog formation. During sea fog development and persistence, liquid water content increased when turbulence exchanges weakened, and vice versa. The changes in turbulence exchanges were closely related to the quasi-periodic oscillations observed in sea fog presence.

Novel Applications for Fog Water Harvesting

In a scenario of climate changes and increasing stress upon available fresh water resources like rivers, lakes and aquifers, collecting fog water is a promising yet relatively unexplored potentiality. Providing sufficient water and reducing water extraction’s environmental impact at the same time can be a challenge with conventional ways, but fog harvesting technology presents itself as a powerful and efficient alternative. Water availability profoundly determined regional economic benefit, social relations and it also influenced environmental security and ecosystem services. Underdeveloped countries have been dealing with water scarcity issue for decades, but also wealthy countries will have to face the water crisis soon, due to unsustainable development processes. A review of the state of the art highlights the most relevant parameters to deal with when discussing about fog water harvesting. In regions with frequent fog events, this technology already proved to be a sustainable drinking water resource for rural communities and their low per capita water usage was provided by basic devices utilization. Nevertheless, in this paper, different fog water harvesting applications are investigated, besides the already existing fresh-water collection, reforestation and agricultural use. Further options, such as building components, outdoor activities and domestic devices are considered, according to different parameters, such as economic benefits, possibility of standardized production, life cycle and market attractiveness. A desirable novel concept would become relevant in specific contexts, thanks to multiple functions, offering locals designed and customized solutions. Also noteworthy are the landscape impact of such devices and the effects of the project in terms of places regeneration, raising awareness and “green” conscience creation. The study of local climatic data and improvement in fog collector applications, integration with architectural and landscape design, will expand the regions where fog harvesting can be applied and its sustainable improvements.

Measurements of Fog Water Deposition on the California Central Coast

Fog deposition is a notable component of the water budget of herbaceous-shrub ecosystems on the central and southern coastal regions of California. This paper presents an analysis of fog water deposition rates and meteorological controls in Big Sur, California. Mesh-screen fog collectors were installed the Brazil Ranch weather station sites to measure fog water during the summer seasons of 2010 and 2011. Fog deposition occurred during 73% of days recorded in 2010 and 87% of days recorded in 2011. The daily average deposition rate was 2.29 L/m2 in 2010 and 3.86 L/m2 in 2011. The meteorological variables which had the greatest influence on prediction of fog deposition were wind speed, wind direction, and the dew-point depression (difference between air temperature and dew point). Based on these results, we hypothesize that high rates of summer fog deposition help sustain the productivity of California coastal vegetation through periods of low rainfall.

长江口一次持续性强浓雾过程特征和成因分析

使用船载观测资料、FNL再分析资料和葵花八号云图资料,对2022年3月11—14日发生于长江口的持续性浓雾过程进行研究分析,并归纳总结了预报的实用性方法。结果表明:本次浓雾过程包含辐射雾和锋面平流雾,持续时间长,影响范围广,雾区在锋面的前后部都相继出现,且锋面移动往往影响着雾的移动。在雾的生消和维持过程中,气温和相对湿度通常呈负相关,温度露点差和能见度呈正相关,当温度露点差大于3℃时,长江口也会有雾生成,但能见度不低于3 km。雾生时段通常盛行偏南风和偏北风,偏西风和西北风则会导致相对湿度迅速下降,不利于雾的形成和维持。可见光云图上雾的特征明显,颜色纹理均匀,边界清晰整齐,外围无丝状或纤维状云系扩散,而红外云图上对应处是一片灰暗区,只有边界隐约可见。

一次入海温带气旋背景下的海雾观测分析和数值模拟

利用0.25°×0.25°逐小时ERA5再分析数据、中国气象局地面观测资料、卫星遥感监测资料以及WRF模式对2021年3月27~28日移入黄海的温带气旋引发大范围的海雾过程进行了观测分析和数值模拟,结果表明:(1)本次海雾发生时气海温差介于0.5℃~2℃,海雾成熟阶段出现了气温低于海温的现象。(2)入海气旋形成的湿空气辐合为海雾的发生和维持提供了水汽条件,低空急流带来的西南暖湿气流促进了逆温层的建立并输送水汽。(3)气旋入海以后,黄海海域出现了“双逆温”的现象,低层的逆温来自于低空急流的暖平流输送,高层的逆温是由气旋后部的干冷空气下沉增温造成。(4)在气旋和低空急流的共同作用下,近海面边界层大气湍流动能增加,这也促进了海雾在垂直方向发展。(5)湍流动能收支的诊断结果显示,切变项在海雾的发生和发展过程占据主导作用,当海雾在垂直方向发展时,湍流动能垂直输送项会明显增大。

开式消雾节水技术在工业循环冷却水中的应用

循环冷却水系统节水是工业企业节水、节能的一个重要环节。常规开式循环冷却水塔因塔顶排放口易产生大量白雾,造成水资源的浪费;新型冷凝模块消雾节水冷却塔技术在消除白雾和节水方面成效显著,近年来受到广泛关注。分析了消雾节水冷却塔的消雾节水及工作原理,并与常规开式冷却塔进行了基本参数、运行费用、投资等方面的初步对比。初步估算,消雾节水冷却塔与常规冷却塔相比,蒸发水量和排污量可减少约20%,设备投资增加约80%,但整体运行费用较低,其投资成本在两年左右即可收回,在化工行业具有较好的应用前景。

浅谈循环水节能技术的研究与应用

本文探讨了循环水节水消雾这一主题,旨在探讨通过循环水系统实现节水减排,同时消除水雾产生的影响。具体而言,本文首先介绍了循环水系统的基本原理和优势,并强调了在水资源日益紧张的情况下,节水减排的重要性。接着详细阐述了循环水系统如何通过有效的水循环利用,降低新鲜水的使用量,减少废水排放,从而达到节约水资源和减少环境污染的目的。另外,本文还讨论了如何通过设计和优化循环水系统,减少水雾的产生。作者指出,适当的设计和运行循环水系统可以有效消除水雾,从而改善环境质量,减少因水雾引起的各种问题。同时,作者还对未来的研究方向进行了展望,指出在循环水系统的设计和优化、新型材料的研发和应用等方面仍有很多工作需要进一步探索和研究。

STUDY ON THE CHEMICAL CHARACTERISTICS OF POLLUTING FOG IN GUANGZHOU AREA IN SPRING

Samples of fog water collected in the area of Guangzhou during February, March and April of 2005 are used in this work to study the chemical composition of fog water in polluting fog there. Three typical episodes of polluting fog are analyzed in terms of ionic concentration and their possible sources. It is found that the concentration of various ions in fog water is much higher than those in rainwater. Fog not only blocks visual range but contains liquid particles that result in high degree of pollution and are very harmful to human health. SO4= is the anion with the highest concentration in fog water, followed by NO3-. For the cation, Ca++ and NH4+ are the highest in concentration. It is then known that rainwater is more acidic than fog water, indicating that ionic concentration of fog water is much higher than that of rainwater, but there are much more buffering materials in fog water, like NH4+ and Ca++. There is significant enrichment of Ca++, SO4=, and Mg++ in fog water. In the Guangzhou area, fog water from polluting fog is mainly influenced continental environment and human activity. The episodes of serious fog pollution during the time have immediate relationships with the presence of abundant water vapor and large amount of polluting aerosol particles.

COMPREHENSIVE ANALYSIS OF THE MACRO-AND MICRO-PHYSICAL CHARACTERISTICS OF DENSE FOG IN THE AREA SOUTH OF THE NANLING MOUNTAINS

Using the composite field observational data collected in the area south of the Nanling Mts. and numerical modeling, the seasonal features of dense fog and visibility, fog drop spectrum and physical concept of fog forming have been analyzed. The occurring frequency of low visibility(≤200 m) is very high with a mean of 24.7%, a maximum of 41.8% from the end of autumn to winter and next spring. The fog processes that occur in the area south of the Nanling Mts. in spring and winter result from the interactions of complicated micro-physical processes, the local terrain, water vapor transportation and the influencing weather system. The fog processes are arisen from advection or windward slope, which is much different from the radiation fog. Cooling condensation due to the air lifted by the local mountain plays an important role in fog formation. Windward slope of the mountain is favorable to the fog formation. Dense fog can occur at lower altitudes in the windward slope of mountain, resulting in the lower visibility. The fog is mainly of small-drop spectrum with smaller number-density than that of urban fog, and its drop spectrum has descending trend in the section of smaller diameter. The inverse relationship between fog water content and visibility is the best among several relationships of micro-variables. In addition to micro-physical processes of fog body itself, the motion of irregular climbing and crossing over hillside while the fog body is being transported by the wind are also important reasons for the fluctuation of micro-physical parameters such as fog water content.

Fog simulation using a mesoscale model in and around the Yodo River Basin,Japan

In this study,fog simulations were conducted using the Fifth-Generation NCAR/Penn State Mesoscale Model (MM5) in and around the Yodo River Basin,Japan.The purpose is to investigate the MM5 performance of fog simulation for long-term periods.The simulations were performed for January,February,March,and July,2005 with a coarse 3-kin and a nested fine 1-km grid domains. Results of the simulations were compared with data from ten meteorological observatories,fog sampling site in Mt.Rokko,and visibility measurem...

CHARACTERISTICS OF QUASI-PERIODIC OSCILLATIONS DURING SEA FOG EVENTS

Based on the high-resolution datasets collected in a sea fog field experiment at the northern coast of South China Sea,the variations of liquid water content (LWC) and net longwave radiation flux (NLRF) during two sea fog events on 16th-17th and 18th-19th March,2008 are exaimeed by wavelet analysis,and the cooling mechanisms for fog formation and persistence are also investigated.The main results are shown as follows.(1) Sea fog may develop and persist whether it is cloudy or not aloft.However,when there is cloud aloft the LWC is less and wind speed in sea fog is higher than that in the clear sky.(2) The quasi-periodic oscillations (QPOs) of NLRF are observed in the formation stage of the two fogs.QPOs of LWC are only found in the developing stage no matter with cloudless or cloudy condition.(3) It is likely that sea fog forms by the cooling effects of longwave radiation and develops through the vertical mixing induced by the radiative cooling at the upper level.(4) During sea fog development and persistence,other mechanisms could also play important roles in fog-layer cooling,such as turbulent heat transport and radiation transport between air-sea interfaces.

Analysis of the Microphysical Structure of Heavy Fog Using a Droplet Spectrometer:A Case Study

The microphysical properties of a long-lasting heavy fog event are examined based on the results from a comprehensive field campaign conducted during the winter of 2006 at Pancheng （32.2°N, 118.7°E）, Jiangsu Province, China. It is demonstrated that the key microphysical properties （liquid water content, fog droplet concentration, mean radius and standard deviation） exhibited positive correlations with one another in general, and that the 5-min-average maximum value of fog liquid water content was sometimes greater than 0.5 g m-3. Further analysis shows that the unique combination of positive correlations likely arose from the simultaneous supply of moist air and fog condensation nuclei associated with the advection of warm air, which further led to high liquid water content. High values of liquid water content and droplet concentration conspired to cause low visibility （〈50 m） for a prolonged period of about 40 h. Examination of the microphysical relationships conditioned by the corresponding autoconversion threshold functions shows that the collision-coalescence process was sometimes likely to occur, weakening the positive correlations induced by droplet activation and condensational growth. Statistical analysis shows that the observed droplet size distribution can be described well by the Gamma distribution.

A Correction Algorithm for Atmospheric Visibility Based on Fog Droplet Size Data Obtained on a Moving Ship During 2016 Arctic Cruise

In this study, we measured the droplet size distribution(DSD) and visibility of sea fog using a fog droplet spectrometer and visibility meter, respectively, during the July 23-August 3 and August 22-September 13 periods of the 2016 Chinese National Arctic Research Expedition. We calculated the visibility using the Mie theory and the DSD data and then compared the calculated with the observed visibility. The comparison shows that the deviations in the calculated visibility caused by DSD data sampling errors cannot be ignored. During navigation, wind and ship speeds tended to push or pull the sampled air and cause turbulence pulsation, which influenced the sampling of the fog droplet spectrometer. This influence is weak when the liquid water content(LWC) is high but becomes stronger as the LWC decreases. Taking the sailing speed and heading into consideration, the wind speed component parallel and perpendicular to the air inlet of the fog droplet spectrometer exhibit different laws in the deviation. By performing a fitting analysis of the calculated and observed visibilities under different wind speeds and wind directions, here, we present two sets of correction coefficients for the two wind-speed components and a method for correcting the calculated visibility. This correction method shows excellent results.

The cooling and moistening effect on the formation of sea fog in the Huanghai Sea

With the sea surface observations from ICOADS for the years 1960-2002, the conditions of coohng, evaporauon anu water vapol transportation are analyzed and compared for the formation of seasonal sea fog in April-July in the Huanghai Sea. It is found that sea surface cooling is always existent during the fog seasons while sea surface evaporation only appears in April-June in the Huanghai Sea. Local evaporation alone is not sufficient to form fogs though it may lead to light ones. Water vapor transported from the low-latitudes accomplished by specific synoptic systems is the most important condition for sea fog formation. In general, the moistening effect is more important than the cooling one.

非降雨水研究进展

非降雨水对干旱和半干旱区的水平衡和生态非常重要。本文归纳总结了非降雨水的测量和模拟方法,分析并综述了研究现状。非降雨水是陆气间较小的通量,时空变异强,直接测定存在困难。利用专门的冷凝器可获得可观的结露量。露水研究集中于干旱与半干旱区的站点尺度,雾水研究集中在沿海和山区,水汽吸附研究主要在旱地。非降雨水的收集利用及其对生态环境的影响是研究热点。然而,露水研究较多,雾水和水汽吸附研究明显偏少。同时,自然表面结露、大空间尺度和长期的研究较少。在非降雨水的时空变化规律认识方面存在明显的知识缺口。

The characteristics of sea fog with different airflow over the Huanghai Sea in boreal spring

Using the observations from ICOADS datasets and contemporaneous NCEP/NCAR reanalysis datasets during 1960-2002,the study classifies the airflows in favor of sea fog over the Huanghai （Yellow） Sea in boreal spring （April-May） with the method of trajectory analysis,and analyzes the changes of proportions of warm and cold sea fogs along different paths of airflow.According to the heat balance equation,we investigate the relationships between the marine meteorological conditions and the proportion of warm and cold sea fog along different airflow paths.The major results are summarized as follows.（1） Sea fogs over the Huanghai Sea in spring are not only warm fog but also cold fog.The proportion of warm fog only accounts for 44% in April,while increases as high as 57% in May.（2） Four primary airflow paths leading to spring sea fog are identified.They are originated from the northwest,east,southeast and southwest of the Huanghai Sea,respectively.The occurrence ratios of the warm sea fog along the east and southeast airflow paths are high of 55% and 70%,while these along the southwest and northwest airflow paths are merely 17.9% and 50%.（3） The key physical processes governing the warm/cold sea fog are heat advection transport,longwave radiation cooling at fog top,solar shortwave warming and latent heat flux between airsea interfaces.（4） The characteristics of sea fog along the four airflow paths relate closely to the conditions of water vapor advection,and the vertical distribution of relative humidity.

逆流式消雾节水冷却塔在制酸系统的应用

介绍了传统湿式冷却塔的工作原理及运行过程中存在的问题,以及逆流式消雾节水冷却塔的结构特点、羽雾消除原理、节水原理和应用效果。针对传统湿式冷却塔存在的羽雾污染问题,金川集团股份有限公司镍冶炼厂提出了采用逆流式消雾节水冷却塔代替传统湿式冷却塔的改造方案。生产实践证明,逆流式消雾节水冷却塔可明显减少冬季冷却塔上方的白雾,且饱和水蒸气冷凝成水滴流入水池可循环使用,起到了消除羽雾和节水的作用,具有较好的环境效益与经济效益。

雾水和降水的氢氧稳定同位素差异及其影响因素

为深入分析不同陆地系统中雾水和降水的氢氧稳定同位素差异及其主要影响因素,在全球尺度下搜集了雾水和降水的氢氧稳定同位素数据,统计分析了不同地区雾水和降水的氢氧稳定同位素特征及二者差异的显著性。结合雾水的lc-excess值,分类讨论并揭示了同位素差异的主要形成原因及其与雾发生类型的关系。结果表明:整体上,雾水比降水更富集重同位素,δ2H和δ18O的差值分别在10‰~60‰和1.2‰~5.5‰之间。根据雾水lc-excess的特征,各地区雾水和降水氢氧稳定同位素差异可分为3类:lc-excess值近似为0,雾水分布在LMWL的95%置信区间内;lc-excess值大于0,雾水分布在LMWL上方;lc-excess值小于0,雾水分布在LMWL下方;这3类差异的主导因素分别为水汽来源、凝结温度、环境湿度。因地形雾、辐射雾、平流雾对应的水汽条件和冷凝过程不同,因此三者与降水的同位素差异也不同:地形雾与降水的同位素无显著差异;辐射雾与降水的同位素组成差异较大,雾水中重同位素明显富集;平流雾与降水的同位素组成重叠区域较小,雾水中的重同位素明显更加富集。

某金属矿山回风井口雾气产生机理及治理研究

云南某金属矿山冬季主回风井口产生的大量浓郁雾气,影响了空气环境及周边居民生活,急需采取针对性措施对其进行治理。通过监测分析该金属矿山回风井内湿空气状态参数,测算雾气析出水量,提出了气液液三相流分离治理措施,并基于该分离治理措施开展了雾气颗粒分离数值模拟计算和现场工业试验,研究了金属矿山回风井口雾气产生的机理,验证气液液三相流分离治理措施的除雾效果。结果表明:该金属矿山回风井口雾气的产生与湿空气的状态变化有关,矿山最优工况条件下回风井口雾气析出水量平均水平为28.58 t/d,并得出了一个快速测算雾气析出水量的函数关系式;气液液三相流分离治理措施在模拟矿山实际回风工况范围内的除雾效率为93.4%~99.6%,且在现场工业试验中达到了明显的除雾效果,对于矿山回风井口雾气治理具有重要的指导意义。

唐山港海雾的环境要素特征和环流背景分析

利用唐山港2015—2019年海雾观测数据,综合美国国家环境预报中心(NCEP)的2.5°×2.5°等压面资料和0.25°×0.25°的全球最终分析资料(FNL),分析了唐山港海雾的时间变化和海雾期间地面气象要素的特征,同时对海雾日数异常的年份和月份的环流形势、水汽条件进行对比分析。结果表明:海雾的发生具有明显的月变化和日变化特征,海雾集中出现在7月和10月—次年1月,且主要发生在凌晨—上午;风速在3级以内的偏南风和偏东风最有利于海雾的发生;当相对湿度超过90%时,唐山港的水平能见度很可能低于500 m;海雾发生期间水温大多低于20℃,水气温差超过5℃的情况约占一半;海雾发生在大气环流比较平直、近地层气压梯度小、风速整体偏弱的偏南风环境中,期间存在一个或多个逆温层,低空暖平流和弱垂直环流为大气增湿和逆温层的形成提供了有利条件;唐山港海雾的年际变化与副热带高压有关,强度大、西脊点西伸且脊线位置偏北的副热带高压更有利于热带洋面暖湿气流的向北输送,平流水汽遇到冷的下垫面易形成海雾,在这样的环流背景下唐山港海雾日数会偏多,反之则偏少。