Fog Conditions Research Articles

The Fog Remote Sensing and Modeling Field Project

The main purpose of this work is to describe a major field project on fog and summarize the preliminary results. Three field phases of the Fog Remote Sensing and Modeling (FRAM) project were conducted over the following two regions of Canada: 1) the Center for Atmospheric Research Experiments (CARE), in Toronto, Ontario (FRAM-C), during the winter of 2005/06, and 2) Lunenburg, Nova Scotia (FRAM-L), during June 2006 and June 2007. Fog conditions observed during FRAM-C were continental in nature, while those conditions observed during FRAM-L were of marine origin. The main objectives of the project were to attain 1) a better description of fog environments, 2) the development of microphysical parameterizations for model applications, 3) the development of remote sensing methods for fog nowcasting/forecasting, 4) an understanding of issues related to instrument capabilities and improvement of the analysis, and 5) an integration of model data with observations to predict and detect fog areas and particle phas...

Perceived Brightness and Saturation of Color LED Light in Dense Fog at Night Time

Nowadays, light-emitting diodes (LED) have been widely used in real-time traffic information boards, traffic lights and vehicle lights effectively. Even though these devices are successfully used in each of their designated fields, these devices are greatly affected under bad weather conditions such as heavy rain and fog. This study determined which LED colors were affected under fog condition using LED display and artificial fog with 100μm droplet size and various densities. By using fog droplet size of 100μm and different fog densities, it is revealed that reddish yellow (RY) color was the least affected under fog influences base by saturation and brightness evaluation given by the subjects.

Perceived Brightness Evaluation of LED Light in Daytime Fog

Investigation of the brightness of LED on traffic information board or traffic signs under foggy conditions is an important practical consideration, because LED becomes fainter and contrast is reduced. Especially when fog occurs at daytime, fogs appear to be whitish. In these conditions brightness of LED is much dispersion into the fog. In this paper, by evaluating LED brightness with human visual sensitivity, it is understood that in daytime fog condition and different fog densities do affecting brightness evaluation. The colored LED light that contains a red component has high brightness evaluation point and the blue component has low brightness evaluation in all fog densities. However, blue color that containing red color also has high evaluation point. This paper result can contribute to air and land traffic safety which can present further accident happen.

Contrast enhancement algorithm for fog-degraded image based on fuzzy logic

Based on the analysis for the fuzzy nature of fog-degraded images,a novel contrast enhancement algorithm based on fuzzy logic was presented.By normalizing the degraded image,the algorithm allayed the impact of different fog conditions on gray levels distribution range.According to the attenuation law of atmospheric contrast in fog weather,the algorithm enhanced the contrast of normalized image in fuzzy region.Experimental results demonstrate that the proposed algorithm can more flexibly and effectively improve the contrast of fog-degraded images.

On the corrosion behaviour of novel high carbon rail steels in simulated cyclic wet–dry salt fog conditions

Eutectoid rail steels are prone to excessive corrosion in the coastal locations in India. In order to minimise this problem, four new rail steels with microalloying elements, Cu, Cr, Ni and Si were designed. The corrosion behaviour of these four rail steels were compared with the behaviour of three rail steels already in commercial application. Quantitative evaluation done by weight loss measurements after simulated wet–dry salt fog exposure test showed similar weight loss values for all rail steels. The FTIR spectra of rust samples revealed the presence of Fe 3− x O 4 as the major phase in both inner and outer layers of rusts on all the rail steels. Relative amounts of the different rust phases have been compared. SEM micrographs of the rusted samples revealed that the rust on Cr–Cu–Ni and Cr–Cu–Ni–Si rail steel was more compact than other rail steels. Impedance spectroscopy showed that the rust formed on Cr–Cu–Ni and Cr–Cu–Ni–Si rail steels resulted in the higher impedance in the high frequency region, compared to other rail steels.

Observational Study on Atmospheric and Oceanic Boundary-Layer Structures Accompanying the Okhotsk Anticyclone under Fog and Non-Fog Conditions

A series of GPS radiosonde and oceanic observations was conducted over the Okhotsk Sea for the first time in July 1998. Under the prevalent anticyclone over the Okhotsk Sea during the observations, distinct differences in the atmospheric and oceanic boundary-layer structure were observed between the fog and non-fog periods. During the fog period, the observed strong surface winds and upward sensible heat fluxes promoted vertical mixing in the atmosphere and ocean. The height of the well-mixed marine boundary layer varied from 200 to 1000m in the atmosphere, and 10 to 15 m in the ocean, respectively. The fog formation occurred when surface air temperature (SAT) was cooler than the underlying sea surface temperature (SST). By trajectory analyses for the observed well-mixed atmospheric boundary layer during the fog period, the boundary-layer air mass that has passed over warm (cool) SST tended to form stratus-like (stratocumulus-like) fog. In the non-fog period, by contrast, atmospheric and oceanic boundary layers were stably stratified due to weak surface winds and downward sensible heat fluxes. Regardless of the air mass trajectory, SAT is warmer than underlying SST during the no-fog period.

An innovative artificial fog production device improved in the European project “FOG”

Transport safety is a major goal in the European Union. Low visibility conditions, especially due to fog, increase the risk of major accidents (chain collision). Innovative products have been developed by the automotive industry, including equipment manufacturers, to increase the level of safety of car passengers and drivers. Testing of these products requires the simulation or artificial reproduction of low visibility (fog) conditions with good stability and reproducibility characteristics. We report on the results of the European Union funded “FOG” project to improve road transport safety through fog production in an experimental test chamber located at the Clermont-Ferrand laboratory for research on road safety and visibility. The project developed a prototype of a small-scale climatic chamber, an improved fog production spraying device, a laser-based visibility measurement device, a reduced scale transmissometer, and a combined indoor climate-fog production simulation software. The ability of the fog chamber to test for driver reaction was also investigated. Recent developments include a device able to produce stable visibility levels and homogeneous fog, representative of various types of natural water droplet distribution. The fog characteristics were determined and compared to natural fog. Results are presented for a selection of conditions including stabilized visibility levels for dense fog and two kinds of droplet distributions.

안개 발생시 도로 조명용 광원의 시인성 연구

본 논문에서는 도로 조영용 광원으로 쓰이는 메탈핼라이드램프, 고압나트륨램프, PLS의 세 가지 광원에 대해 안개 발생시 시인성을 평가하기 위해 특정한 인공 안개 조건하에서 각 광원들에 대한 피시험자들의 평가를 분석하여 명소시에는 고압나트륨램프가 시인성이 좋고 암소시에는 PLS가 시인성이 좋다는 결과를 얻었으며 이 결과는 앞으로의 도로 조명용 광원의 선택에 있어서 도움을 줄 수 있을 것으로 기대된다.

Microphysical Observations and Mesoscale Model Simulation of a Warm Fog Case during FRAM Project

The objective of this work is to apply a new microphysical parameterization for fog visibility for potential use in numerical weather forecast simulations, and to compare the results with ground-based observations. The observations from the Fog Remote Sensing And Modeling (FRAM) field which took place during the winter of 2005 – 2006 over southern Ontario, Canada (Phase I) were used in the analysis. The liquid water content (LWC), droplet number concentration (Nd), and temperature (T) were obtained from the fog measuring device (FMD) spectra and Rosemount probe, correspondingly. The visibility (Vis) from a visibility meter, liquid water path from microwave radiometers (MWR), and inferred fog properties such as mean volume diameter, LWC, and Nd were also used in the analysis. The results showed that Vis is nonlinearly related to both LWC and Nd. Comparisons between newly derived parameterizations and the ones already in use as a function of LWC suggested that if models can predict the total Nd and LWC at each time step using a detailed microphysics parameterization, Vis can then be calculated for warm fog conditions. Using outputs from the Canadian Mesoscale Compressible Community (MC2) model, being tested with a new multi-moment bulk microphysical scheme, the new Vis parameterization resulted in more accurate Vis values where the correction reached up to 20 –50%.

Evaluating patterns of fog water deposition and isotopic composition on the California Channel Islands

Fog deposition is an important water source for endemic conifer species during the annual summer drought along the California coast (and in other coastal and montane areas). We present a new design for a passive fog collector that is useful both for characterizing fog regimes (timing and quantity of deposition) and for collecting fog water for subsequent isotopic analysis. The new collector both mimics vegetation collection efficiency and minimizes isotopic fractionation under a range of fog conditions. Low construction cost and collector durability allow widely distributed installation and greater insight into spatially heterogeneous fog patterns. We installed 21 fog collectors throughout a stand of Bishop pines (Pinus muricata D. Don) on Santa Cruz Island. In general, there was greater fog deposition with increasing elevation and decreasing frequency farther inland. Within these broad patterns, there was large spatial and temporal variability in fog deposition. Monthly samples of fog and rain waters reveal differences in stable isotope composition (δ18O and δD) large enough to serve as tracers of different water sources moving through the ecosystem.

Black carbon aerosols and gaseous pollutants in an urban area in North India during a fog period

Northern regions of India experience severe fog conditions during the winter period (December–January) each year. In the present study, concurrent measurements of black carbon aerosols (BC), Carbon monoxide (CO), Surface Ozone (O 3) and oxides of Nitrgen (NO x ) have been carried out in Allahabad, located in northern India in order to understand the impact on pollutant concentrations during fog periods. The results of the present study show higher concentrations of BC, NO x and CO during morning and late night hours in the study area. Diurnal variations of ozone concentrations varied from 14 ppbv to 35 ppbv and were observed to increase gradually after sunrise attaining a maximum value by evening time and to decrease gradually thereafter. Concentrations of BC, NO x , O 3 and CO were found to be very low during fog periods over the study area. BC showed a positive correlation with CO and a negative correlation with surface ozone concentrations. The slope between black carbon aerosols and ground level ozone suggests that every 1 μg m − 3 increase in black carbon aerosol mass concentration causes a reduction of 0.7 μg m − 3 surface ozone.

Greenhouse Microclimate and Soilless Pepper Crop Production and Quality as Affected by a Fog Evaporative Cooling System

The influence of greenhouse humidity control on greenhouse microclimate, crop transpiration rate, and yield and fruit quality of a soilless grown pepper crop was studied in a greenhouse located at the coastal area of western Greece. Measurements were carried out during summer and autumn in two distinct greenhouse compartments involving: (1) no air humidity control and (2) a fog system operating when the relative humidity of the greenhouse air was lower than 80%. Under fog conditions, the greenhouse air and the crop leaf temperature were about 3°C lower than those measured under no fog conditions. The fog system allowed maintenance of the greenhouse air temperature under 30°C, while a maximum value of about 35°C was reached under no fog conditions. In addition, under fog conditions, the air vapor pressure deficit was lower than 2 kPa, even during the warmest part of the day, while under no fog conditions it reached values near 4 kPa. However, the transpiration rate was not affected to such an extent by fog as the air vapor pressure deficit, and under fog conditions it decreased by about 26%. This is attributed to the values reached by the bulk stomatal conductance, which were about 1.5 times higher under fog than under no fog conditions. The crop leaf area index values observed after the middle of the experimental period and later, under fog conditions, were higher than that observed under no fog conditions. Finally, the fog system enhanced the mean fruit weight and the percentage of marketable fruits but reduced appreciably the total number of fruits per plant. The free (titratable) acidity and the total soluble solids in the pepper fruit sap were slightly reduced by the fog cooling system, while the fruit size was increased. The use of a fog cooling system proved to be beneficial for summer crops of pepper grown under Mediterranean climatic conditions due to a favorable impact of the reduced vapor pressure deficit on both the mean fruit weight and the quality in terms of fruits graded Class I. Nevertheless, the high air humidity imposed by a cooling fog system may reduce the number of fruits per plant, thereby offsetting the benefits from the increased mean fruit weight in terms of total yield.

Effect of variable message signs on driver speed behavior on a section of expressway under adverse fog conditions—A driving simulator approach

AbstractVariable message signs (VMS) are used to provide dynamic information and one current application is to show different speed limits under different conditions. As speed is an important contributor to road accidents and also affects driver speed behavior, the present study focuses on how effective traffic advisory information is when helping drivers to divert from potentially dangerous conditions. Graphical representation of an Expressway section made it easy to isolate the effects of speed etc. by drivers with information provided through VMS under adverse fog conditions. Understanding and reacting to the VMS system by drivers is essential for its success. If drivers do not react by changing speed behavior then the VMS system will fail and further implementation may cease. In this paper an Analysis of Variance model, which is appropriate to the proposed experimental conditions, is used to study how subjects (drivers) will perceive provided information and also to find the effect of VMS on driver speed behavior on the simulated Expressway section.

Car following decisions under three visibility conditions and two speeds tested with a driving simulator

The National Highway Traffic Safety Administration web site reports that rear-end collisions in the United States exceed 1.5 million per year, or approximately 23% of all vehicle crashes. Car following behavior and the decision-making habits of drivers seem fundamental to understanding how to avoid these rear-end crashes. The present research aimed to reveal factors that govern car following under conditions of reduced visibility. It employed a KQ-Vection high-fidelity driving simulator to measure the behavior of automobile drivers following a lead vehicle at 13.4 m/s (30 MPH) or 22.4 m/s (50 MPH) under three visibility conditions—clear or one of two densities of simulated fog. At the higher speed, fog conditions separated participants into a group that stayed within visible range of the lead car, even though the headway time violated the NHTSA recommendations for the speed involved, and another group that lagged beyond the visible range. Data were compared to the model of Van Winsum for car following (The human element in car following models. Transportation Research Part F 2, 1999). Contrast and image size measurements allowed comparison to a standard contrast sensitivity function and allowed estimation of the JND term in the Van Winsum model.

Effect of core diameter of cylindrical polymer insulators on contamination flashover voltage—part I

AbstractThis paper presents the investigation results of the effect of the core diameter on the flashover voltage of cylindrical polymer insulators under contaminated and heavy fog conditions. The specimens had the same or very similar shed profiles but different core diameters. The results confirmed a large reduction in flashover voltage when the core diameter was increased from 26 mm for transmission line insulators to 73 mm for post insulators; however, change is not so significant from post insulators to bushing shells having larger core diameters. Higher flashover voltages of line insulators are attributable to the large difference in the leakage current density between the trunk and shed portions so that the wetting conditions are very different between these portions. This causes the applied voltage to the whole insulator to be divided and allotted to almost all the dried trunks, preventing the concentration of the applied voltage to only a few portions, resulting in higher flashover voltages. The quantitative assessment of contamination flashover voltage characteristics of hydrophobic polymer insulators presented in this paper will be helpful in the selection and design of polymer insulators for contamination areas. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Mercury in fog on the Bay of Fundy (Canada)

Mercury concentrations in fog water, collected during the summer of 2003, were found to vary along a geospatial gradient from Grand Manan (an island at the mouth of the Bay of Fundy, with Hg levels 42–435 ng l −1), the main coastline of New Brunswick at Point Lepreau (2–33 ng l −1), to an inland location in Fredericton, Canada (3.5 ng l −1). Hg concentrations were higher during days when air masses were stationary and fog conditions were extended over several days. High concentrations on Grand Manan were most likely due to continued atmospheric deposition of Hg into fog banks of long duration, high air turbulence along the steep 100 m cliffs, and decreasing droplet size with increasing air temperature during the course of the day. We found that fog Hg deposition was about 0.4–7.5% of wet Hg deposition along the coastal area, whereas on Grand Manan Island, fog Hg deposition from was 31–74% of wet Hg deposition.

Quantum cascade laser-based free space optical communications

The advent of the quantum cascade laser (QCL) with emission wavelengths available in the infrared range from 3 µm through more than 100 µm opens up the possibility of exploiting infrared atmospheric transparency windows for free space optical communications. In an effort to establish the efficacy of using directly modulated QCLs for free space communications we have conducted a series of investigations that demonstrate the potential advantages of this technology. In these experiments we first establish that the QCL has very high modulation bandwidth. We then implement a practical free space communications link that under conditions of atmospheric fog, dust and other obscurants offers significant transparency advantage when compared with near infrared wavelength sources presently used in commercial free space optical communications links.

Effects of chronic acid fog exposure with soil acidification or nitrogen loading on nutrient status in Abies firma seedlings

To clarify the nutrient status in momi fir (Abies firma Sieb. et Zucc.) seedlings under complex stress conditions of acid fog with soil acidification or nitrogen loading, we exposed seedling shoots to simulated acid fog (pH 3) and simultaneously loaded the soil with acid or excess nitrogen for 17 months. Proton and nitrogen loading reduced K concentration in soil, but these treatments had little effect on the nutrient status of fine roots in momi fir seedlings. Acid fog exposure resulted in reduced concentrations of Mg, Al, and Fe in current-year needles and Mg, Al, Cu, Fe, and Zn in 1-year-old needles. The complex effects of acid fog exposure with proton or nitrogen loading on nutrient status were relatively slight. However, elements such as Al and Cu notably reflect the effects of proton loading. These results show that the nutrient status of trace elements, rather than major elements, in needles of momi fir seedlings is sensitive to exposure to acid fog or proton loading.

Coastal Fog, Satellite Imagery, and Drinking Water: Student Fieldwork in the Atacama Desert

This paper discusses the role played by undergraduate geography students at the Pontifical Catholic University of Chile in conducting research on advection fog in the Tarapaca Region of the Atacama Desert. Research results show that an enormous amount of fog water can be collected for domestic purposes, productive activities and in the restoration of degraded ecosystems. Students are involved in intensive fieldwork measuring, spatially, stratocumulus clouds and fog conditions and comparing results with GOES imagery. Within the geography program students are expected to participate in four field experiences as part of their training. This research endeavor provides them an excellent opportunity to gain such experience.

Effect of Time and Foggy Conditions on Subjective Visibility

In dense fog, the visibility of retroreflective traffic control devices is vital for driving safety. However, few studies have addressed the visibility of such devices in fog during a 24-h period (daytime, evening, and nighttime). This study measures the subjective visibility of the latest traffic control devices under various visibility conditions. An experiment was performed during a 2-month period in 2003 under natural fog at a test road 200 m long and 7.5 m wide in Eastern Hokkaido, Japan. Visibility conditions varied by daytime, evening, and nighttime and by weather condition factor (clear, cloudy, and dense fog). Thirteen kinds of traffic control devices were used as targets: two types of pavement markings, three of delineators, four of warning signs, and four of chevrons. Various newly developed materials were tested, and color and size were varied. The 20 women who participated in the experiment were required to make subjective judgments within a few seconds of the visibility of each target and their feeling of safety, assuming that they were driving on that section at 50 km/h. Results showed that daytime fog had a major negative effect on subjective visibility evaluations, while nighttime fog did not have as great a negative effect as that in daytime. However, the subjective visibility values of targets under the nighttime cloudy condition were worse than those under the daytime dense fog condition. Also, subjective visibility values for target objects made of highly reflective materials or incorporating fluorescent colors were high under both daytime fog and nighttime fog conditions.