Visibility Reduction Research Articles

Adaptive tone mapping for display enhancement under ambient light using constrained optimization

We propose adaptive tone mapping for display enhancement under ambient light using constrained optimization. To deal with the visibility reduction caused by ambient light in displays, we perform different operations for display enhancement according to the intensity of ambient light. Since weak ambient light has little effect on displayed images, we only perform contrast enhancement for them. However, strong ambient light makes displayed images dark for human eyes, causing severe visibility reduction in luminance and contrast. To enhance the visibility of displayed images under strong ambient light, we formulate a constraint optimization problem which consists of luminance enhancement, contrast enhancement, and distortion minimization terms, and find an optimal trade-off among them by solving it. Finally, we conduct color scaling to reproduce vivid colors in displayed images. Experimental results demonstrate that the proposed method significantly enhances the brightness, contrast, details, and colors of displayed images and outperforms other state-of-the-art methods under ambient light.

Bottom-up emission inventories of multiple air pollutants from open straw burning: A case study of Jiangsu province, Eastern China

Open straw burnings during harvest season generated large amounts of air pollutants in a short duration, resulting in significant visibility reduction, air quality deterioration and adverse impact on human health. In this study, a bottom-up approach of county level emission inventory from open straw burning was developed. A 1 km resolution inventories for Jiangsu province, Eastern China, was established as a case study. In order to increase temporal-spatial resolution, county level, seasonal data and local parameters were preferentially used. Per capita disposable income of rural residents was used to adjust burning proportion for different cities. Emissions during summer-harvest and autumn-harvest seasons were calculated separately. The inventory was further allocated based on both MODIS fire product and land use data of cropland. Total emissions of SO2, NOx, THC, NH3, OC, BC and primary PM2.5 from open straw burning in 2015 were 3.72, 15.25, 43.52, 2.65, 16.08, 2.08 and 44.70 Gg, respectively. From 2010 to 2015, provincial emissions decreased by 50.7% in average, and the difference between southern and northern Jiangsu has been even enlarged. Autumn-harvest crop straw contributed 63%–67% to NH3, OC and PM2.5, while summer-harvest crop straw contributed 60% to BC. Wheat and rice straws burning accounted for the majority of emissions at 80%–91% of the total for all 7 pollutants. Uncertainties ranged from a low of within 29% for BC to a high of within 40% for NH3. The EFs and the crop production of autumn-harvest rice and summer harvest wheat, are the key uncertainty sources.

‘Am I not an Author?’ Social class and the contemporary French novel

ABSTRACTWhile the term ‘working-class’ has fallen out of usage as the concept of class has lost its visibility and its power as a métarécit, this does not mean the issues that this term evokes have gone away. The hardship that comes of particular working lives, as well as the values and culture which are distinct from dominant bourgeois values, still exist. Indeed, in a France and a Europe in which inequality is growing, and in which ‘précarité’ has become an everyday term, how is this reality represented in the contemporary French novel? Through a discussion of the relationships between class, society and literature, this article will explore the tensions between the literary world and the working-class novel. It will then turn to the work of contemporary writers Olivier Adam and Edouard Louis, who not only engage with issues of social class in their creative work, but equally condemn the disconnect between literature and society on the French literary scene. This article will show that working-class experience has potentially been sidelined not only as a result of the reduction in visibility of the very idea of social class, but also as a result of the French literary scene’s approach to literature.

Characteristics of visibility-impairing aerosol observed during the routine monitoring periods in Gwangju, Korea

Aerosol chemistry measurements were performed during the routine monitoring periods in the urban atmosphere of Gwangju, Korea. Routine aerosol monitoring was carried out every sixth day in order to investigate the dependence of domestic sources and air mass transport characteristics on physicochemical and optical properties of atmospheric aerosol. Aerosol optical properties; atmospheric extinction and scattering coefficients were also measured continuously with a transmissometer and a nephelometer, respectively in order to investigate the causes of visibility impairment. Prevailing atmospheric condition was classified into four categories; one affected by stagnant condition (D), one affected by continental and domestic aerosols (CD), one affected by marine and domestic aerosols (MD), and one affected by continental, marine and domestic aerosols (CMD). Atmospheric condition type was further classified into thirteen sub-categories with the occurrences of episodic events such as Asian dust storm, biomass burning, and airborne pollen. The air mass types of D, CD, MD, and CMD were observed to be 11, 18, 43, and 78 events out of total 150 events, respectively. The fine mass concentration increased under continental air mass types. The average fine mass concentration of 23.0 ± 8.6 μg m−3 for CD type was slightly larger than that of 20.7 ± 5.2 μg m−3 for CMD type. Both of them were higher than that for D (18.9 ± 4.5 μg m−3) type. Increments of the fine mass concentrations for Asian dust storm (A) and Biomass-burning (B) events ranged from 141 to 151% and from 152 to 160% compared to those for D and CD types, respectively. The increments in the mass concentrations of nitrate, OC, EC, and BC for CD and CMD types in comparison with D air mass type were calculated to be approximately 17, 6, 8, and 22%, respectively. The mean mass extinction efficiency of PM10 was relatively higher in D (3.6 ± 1.6 m2 g−1) type and B events (4.1 ± 1.5 m2 g−1), but it was the lowest in MD air mass type. The aerosols observed in Gwangju were found to be influenced by the continental aerosol during the A events. Aerosol of CMD air mass type caused mainly poor visibility. The visibility reduction of Gwangju was influenced by the increase of carbonaceous particles under both domestically stagnant condition and air mass pathway from the continent. And ammonium sulfates and ammonium nitrates contributed the largest in CMD air mass type.

PM10 and PM2.5 from Haze Smog and Visibility Effect in Chiang Mai Province Thailand

Air pollution from haze smog in Chiang Mai Thailand has become a serious problem, with fine particulate matter (FPM), PM10and PM2.5, as the main culprits. These pollutants haveserious effects on health and affect visibility in transportation and tourism. In this study, reduction in visibility was monitored using a digital camera, video records and aerial photography. Visibility in Chiang Mai was analyzed using qualitative and quantitative methods. Visibility was directly measured by GPS and Google Earth mapping. Visibility reduction from haze events was also compared by image analysis in Deciview units. Fine particulate matter concentrations and frequency of fires in Chiang Mai were associated with visibility reduction. Forest fires increased Deciview numbers. In the dry season, the frequency of fire incidents was correlated with both PM10and PM2.5with R2= 0.9 (95% CI, p<0.05). The reversecorrelation (-R2) between visual length (km) and PM10and PM2.5were 0.64 and 0.72 at altitude444 m with 95% CI, p<0.05. The reverse correlation (-R2), at altitude 313 m was 0.93for PM10and 0.96 for PM2.5with 95% CI, p<0.05. The reverse correlation (-R2), at altitude 324 m was 0.86 for PM10 and 0.93 for PM2.5with 95% CI, p<0.05. The association between visibility and FPMat low altitude was found to be more significant than at high altitude.

Influence of intensified air pollution on the sunny diffuse radiation fraction in China

In recent years, air pollution has been getting increasingly serious in China—A cause of great concern for the government and general public. Research on air pollution has focused mainly on the environmental and climatic effects, such as the increasing number of haze days, reduction in visibility, human health impacts, suppression of global warming, extension of cloud life, restriction of light precipitation, and weakening of the East Asian monsoon. In fact, the exacerbation of air pollution might also affect the radiation balance of the surface-atmosphere system, with subsequent direct impacts in areas of socioeconomic concern like agricultural production. However, domestically, research in this area is currently lacking. Accordingly, the present study, based mainly on the sunny diffuse radiation fraction (SDRF—defined as the diffuse solar radiation divided by the total solar radiation in conditions of sunny weather) at 47 stations over China, combined with CO2 emissions data, aerosol optical depth (AOD) and sunshine duration data, analyzes the spatiotemporal variation of SDRF in China and the possible determining factors. The results provide a reference and basis for the accurate assessment of terrestrial ecosystem productivity and its carbon budget. Analysis of the SDRF distribution reveals clear regional characteristics in China, with relatively larger values distributed mainly in the Sichuan Basin and Central China. However, the values of SDRF in Yunnan, Xinjiang, Tibet and Northeast China are small. The majority of stations show an obvious upward trend in SDRF, especially in Eastern China, where the upward trend is more significant than in other regions. Therefore, after removal of the effects of cloud, aerosols should be considered a factor with important influence on the SDRF during the past 50 years. Analysis of the characteristics in each region shows that the increase in SDRF is more obvious in North China, East China and Central China than in South China, Northeast China, Northwest China and Southwest China. This indicates that, in regions where air pollution is more serious, the decline in SDRF is more significant. Sunshine duration in sunny weather is highly correlated with SDRF, with the correlation coefficient in East China, Central China and North China often exceeding −0.8 (statistically significant at the 99.9% confidence level). This result implies that an increase in the concentration of aerosol particles in the air has a significant impact on sunshine duration and SDRF over China.

Monitoring temporal–spatial variations of AOD over the Yangtze River Delta, China

Aerosol can induce visibility reduction, affect radiation balance and modify cloud property on the environmental effect, and show the harmful effects on human health. Insight of aerosol becomes an integral task in the process of control measures for environmental pollution. The present study provided an analysis of temporal–spatial variations of aerosol optical depth (AOD) using the MOD04 level-2 in collection 6 (C6) with the deep blue retrieval algorithm from January 2005 to December 2015 over Yangtze River Delta (YRD) in China. The AOD validations between MODIS and Aerosol Robotic Network (AERONET) were estimated by the methods of regression, correlation. Then, the periodic features and trends of AOD and angstrom exponent (AE) were explored with the wavelet transformation (WT) procedure. Further, the variations of AOD and AE spatial distribution on multi-time scales (annual, monthly and season) were demonstrated. Meantime, the sources of AOD are discussed. It was found that the daily AOD from MODIS has a strong correlation relationship (slope = 0.9838, r = 0.84) with AERONET over YRD. The variations of both AOD and AE on time series have been distinct temporal periodic (12, 6 and 4 months) characteristics, and show the decreasing trends on annual and semi-annual periods. On annual, the AOD on spatial distribution is slowly declining from the northwest towards the southeast, and the AE on spatial distribution is gradually decreasing from the northwest to the southeast and from the land to the coast. The variations both inter-annual AOD and AE on spatial distribution show the inverse trends, respectively. On monthly, the means of AOD range from minimum 0.46 in January to maximum 0.90 in July, and the variations of spatial distribution mainly occur in the north parts of Yangtze River and some scattered areas with high terrain and south coast. The means of AE range from minimum 1.13 in October to maximum 1.58 in April, and the variations of spatial distribution are mainly found in the south of Henan, the north of Jiangsu, the coast belt and the riverside of Yangtze River and the high terrain regions. On seasonality, the means of AOD reaches its maximum 0.68 in summer and minimum 0.50 in winter, and the variations of spatial distribution mainly occur in the coast belt, the north parts of Hongze Lake and the south parts with high terrain. The means of AE reaches its maximum 1.48 in spring and minimum 1.25 in autumn, and the variations of spatial distribution were shown the similarity with that of monthly.

Understanding and Reducing False Alarms in Observational Fog Prediction

The reduction in visibility that accompanies fog events presents a hazard to human safety and navigation. However, accurate fog prediction remains elusive, with numerical methods often unable to capture the conditions of fog formation, and observational methods having high false-alarm rates in order to obtain high hit rates of prediction. In this work, 5 years of observations from the Cabauw Experimental Site for Atmospheric Research are used to further investigate how false alarms may be reduced using the statistical method for diagnosing radiation-fog events from observations developed by Menut et al. (Boundary-Layer Meteorol 150:277–297, 2014). The method is assessed for forecast lead times of 1–6 h and implementing four optimization schemes to tune the prediction for different needs, compromising between confidence and risk. Prediction scores improve significantly with decreased lead time, with the possibility of achieving a hit rate of over 90% and a false-alarm rate of just 13%. In total, a further 31 combinations of predictive variables beyond the original combination are explored (including mostly, e.g., variables related to moisture and static stability of the boundary layer). Little change to the prediction scores indicates any appropriate combination of variables that measure saturation, turbulence, and near-surface cooling can be used. The remaining false-alarm periods are manually assessed, identifying the lack of spatio–temporal information (such as the temporal evolution of the local conditions and the advective history of the airmass) as the ultimate limiting factor in the methodology’s predictive capabilities. Future observational studies are recommended that investigate the near-surface evolution of fog and the role of non-local heterogeneity on fog formation.

The effects of zoo visitors on Quokka (Setonix brachyurus) avoidance behavior in a walk-through exhibit.

The behavior of zoo animals may be influenced by visitors, with possible implications on animal welfare. We examined the effects of the presence of visitors on the presence and visibility of free-ranging quokkas (Setonix brachyurus) in preferred areas of a walk-through enclosure at Melbourne Zoo, Australia. In a controlled experiment, two visitor treatments were randomly imposed: (1) enclosure open to visitors as normal ("Open") and (2) enclosure closed to visitors ("Closed"). Treatments were imposed for 2-day periods, with five replicates of each treatment (10 2-day periods in total). Instantaneous point sampling of camera footage at 1-min intervals from 09:00 to 16:00 hr each day recorded the location and visibility of quokkas. Data were analyzed using a two-factor ANOVA (visitor treatment and study area), with 2-day summary values as the unit of analysis. While the presence of quokkas in the study areas was not affected by treatment, fewer (p < 0.05) quokkas were visible from the visitor paths and more (p < 0.05) quokkas were obscured from the visitor paths in the "Open" treatment than the "Closed" treatment. Number of quokkas differed between study areas across treatments (p < 0.01), but there was no interaction (p > 0.05) between visitor treatment and study area. The reduction in quokka visibility when visitors were present indicates that visitors were at least moderately fear provoking for the quokkas in this experiment, but further research is required to examine the effects of visitor presence and behaviors on the behavior and stress physiology of quokkas in walk-through enclosures, as there may be possible welfare implications.

Dust and dust storms over Kuwait: Ground-based and satellite observations

We investigate the consistency between Aerosol Optical Depth (AOD) retrieved by MODerate resolution Imaging Spectroradiometer (MODIS) sensor aboard NASA's Aqua satellite and measurements collected by ground-based AErosol RObotic NETwork (AERONET) site in Kuwait for 2007–2012. A good correlation (r = 0.7) is obtained between the two data sets. The volume size distributions (VSDs) of particles with geometric mean radius ranges of 0.05–15 μm has been studied as well. Seasonal variations are clearly found in the shape and magnitude of the VSDs for fine and coarse particles. The VSD of aerosol coarse particles was the highest during spring and summer. It increases substantially during dust storms, reaching the highest value during the dust storm of 24 May 2012. Satellite lidar observations from CALIPSO reveals a moderate vertical extent of the dust storms with the highest extinction coefficients below 500 m height. The method of superposed epoch analysis is used to test the behavior of meteorological parameters during the dusty days of 2012. Increase in wind speed together with significant reductions in visibility and diurnal temperature range (DTR) during dusty days are observed. Additionally, air temperature decreases one day after dust events. This effect can be due to scattering of sunlight back to space by the suspended dust particles.

Investigation of the impact of a wireless Fog Warning System with respect to road traffic on a highway

Sudden visibility reductions on highways due to foggy weather conditions often lead to a drastic increase in car crash risks. Indeed, fog formation distorts drivers’ perception and judgment of inter-vehicular distances, vehicles’ speeds, and braking distances. In order to support drivers in dealing with the impact of fog, various on-board warning systems are being deployed today. Despite their added value, these systems are still in need of efficient solutions supporting smooth vehicle’s acceleration/deceleration profiles. This is to avoid sudden braking (hence, higher car crash risks) incurred by sensor technologies restricted to line of sight measurements. To meet this goal, we advocate in this paper a Wireless Fog Warning System (WFWS) where cooperative awareness messages are disseminated and used for calculating acceleration/deceleration activities. Without loss of generality, we build on IEEE 802.11p WLAN as a basis technology. Using simulations on the open-source vehicular network simulation framework Veins, we demonstrate both the potential of such a system for increasing safety and smoothing traffic flow—as well as of computer simulation as a means of its evaluation.

Automatic Sea Fog Detection and Estimation of Visibility Distance on CCTV

Choi, Y.; Choe, H.-G.; Choi, J.Y.; Kim, K.T.; Kim, J.-B., and Kim, N.-I., 2018. Automatic sea fog detection and estimation of visibility distance on CCTV. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 881–885. Coconut Creek (Florida), ISSN 0749-0208.Sea fog is one of the major maritime disasters and thus causes social costs such as transport accidents, mainly due to the reduction of visibility. However, the optical fog sensors are heavily cost so that sea fog detection system is generally difficult to install in practical applications. In this paper, we present a new technique for detecting sea fog and measuring visibility distances using Closed-circuit television (CCTV). Our research is focused on the problem of detecting daytime sea fog and estimating visibility distances in an automatic way. To this end, we exploit that (1) the image analysis based on the HSL (Hue, Saturation, and Lightness) color model is effective for evaluating the density of sea fog and (2) the movement detection system relying on the variance of the pixel values is capable of deciding the visibility distances. The proposed method has advantage of being readily applicable to the widely used CCTV system without additional devices. This paper also explores the possibility of sea fog detection using deep-learning framework. In our method, Deep Convolution Neural Network (DCNN) end-to-end learning solution has been designed and tested for evaluating sea fog detection performance in the course of popular artificial intelligence framework.

Effects of human activities and climate change on the reduction of visibility in Beijing over the past 36 years

Both climate change and intensive human activities are thought to have contributed to the impairment of atmospheric visibility in Beijing. But the detailed processes involved and relative roles of human activities and climate change have not been quantified. Optical extinction of aerosols, the inverse of meteorological visibility is especially sensitive to fine particles <1.0 μm. These submicron particles are considered more hazardous than larger ones in terms of cardiovascular and respiratory diseases. Here we used the aerosol optical extinction (inverse of visibility) as the indicator of submicron particles pollution to estimate its inter-annual variability from 1980 to 2015. Our results indicated that optical extinction experienced two different periods: a weakly increasing stage (1980–2005) and a rapidly increasing stage (2005–2015). We attributed the variations of optical extinction to the joint effects of human activities and climate change. Over the past 36 years, human activities played a leading role in the increase of optical extinction, with a positive contribution of 0.077 km−1/10 y. While under the effects of climate change, optical extinction firstly decreased by 0.035 km−1/10 y until 2005 and then increased by 0.087 km−1/10 y. Detailed analysis revealed that the abrupt change (around 2005) of optical extinction resulted from the trend reversals of climate change. We found since 2005 the decreasing trend by 0.58 m·s−1/10 y in wind speed, the growing trend at 8.69%/10 y in relative humidity and the declining trend by 2.72 hPa/10 y in atmospheric pressure have caused the rapid increase of optical extinction. In brief, the higher load of fine particles <1.0 μm in Beijing in recent decades could be associated with both human activities and climate change. Particularly after 2005, the adverse climate change aggravated the situation of submicron particles pollution.

Effect of Relative Humidity on Particulate Matter Concentration and Visibility During Winter in Chengdu

The effect of relative humidity (RH) on particulate matter concentrations and atmosphere visibility were investigated using the continuous on-line observed data of Chengdu city during December 2015, including RH, visibility, the concentrations of particulate matters (PM10, PM2.5 and PM1) and gaseous pollutants (SO2 and NO2), and the concentrations of SO42- and NO3- in PM2.5. The results showed that the haze process occurred because of the synergistic effects of higher particulate matter concentrations and RH, leading to the reduction of visibility. The average ratio of PM2.5 to PM10 was 64% and it significantly increased with the increase of RH during observation period, which indicated that the pollution of fine particles during winter in Chengdu was serious, and high RH aggravated the pollution caused by fine particles.Visibility decreased exponentially with the increase of particulate matter concentrations. When RH was higher, visibility was lower at the same concentrations of particulate matter.RH had a strong effect on visibility at lower particle concentrations, while the effect of RH on the visibility decreased, and atmospheric extinction was controlled by PM2.5 concentrations at higher particle concentrations. With RH increasing from less than 40% to more than 70%, the average sulfur oxidation ratio (SOR) and nitrogen oxidation ratio (NOR) increased from 0.27 and 0.11 to 0.40 and 0.19, respectively, indicating that higher RH significantly promoted the formation of secondary sulfate and nitrate. Secondary sulfate and nitrate separately or coordinatively influenced the air quality.

Utilizing naturalistic driving data for in-depth analysis of driver lane-keeping behavior in rain: Non-parametric MARS and parametric logistic regression modeling approaches

It is known that adverse weather conditions can affect driver performance due to reduction in visibility and slippery surface conditions. Lane keeping is one of the main factors that might be affected by weather conditions. Most of the previous studies on lane keeping have investigated driver lane-keeping performance from driver inattention perspective. In addition, the majority of previous lane-keeping studies have been conducted in controlled environments such as driving simulators. Therefore, there is a lack of studies that investigate driver lane-keeping ability considering adverse weather conditions in naturalistic settings. In this study, the relationship between weather conditions and driver lane-keeping performance was investigated using the SHRP2 naturalistic driving data for 141 drivers between 19 and 89 years of age. Moreover, a threshold was introduced to differentiate lane keeping and lane changing in naturalistic driving data. Two lane-keeping models were developed using the logistic regression and multivariate adaptive regression splines (MARS) to better understand factors affecting driver lane-keeping ability considering adverse weather conditions. The results revealed that heavy rain can significantly increase the standard deviation of lane position (SDLP), which is a very widely used method for analyzing lane-keeping ability. It was also found that traffic conditions, driver age and experience, and posted speed limits have significant effects on driver lane-keeping ability. An interesting finding of this study is that drivers have a better lane-keeping ability in roadways with higher posted speed limits. The results from this study might provide better insights into understanding the complex effect of adverse weather conditions on driver behavior.

Potential impact of particulate matter less than 10 micron (PM10) to ambient air quality of Jakarta and Palembang

Particulate is a main urban air pollutant affects the environment and human wellbeing. The purpose of this study is to analyze the impact of particulate matter less than 10 micron (PM10) to ambient air quality of Jakarta and Palembang. The analysis is done with calendarPlot Function of openair model, which is based on the calculation of Pollutant Standards Index (PSI) or better known as Air Quality Index (AQI). The AQI category of “moderate” dominates Jakarta’s calendar from 2015 to 2016, which indicates the impact of PM10 is the visibility reduction. There was one day with category “unhealthy” that indicates the impact of dust exposure everywhere in Jakarta during 2015. Similar to Jakarta, the AQI category “moderate” also dominates Palembang’s calendar during 2015. However, the AQI category “hazardous” happened for few days in September and October 2015 during forest fires, which indicates the more harmful impacts of PM10, such as reduced visibility, dust exposure everywhere, increased sensitivity in patients with asthma and bronchitis to respiratory illness in all exposed populations. During 2016, AQI category of Jakarta mostly “moderate”, while in Palembang was “good”. Dominant AQI category from 2015 to 2016 shows higher PM10 concentration occurred in Jakarta compared to Palembang.

On the Alternative Approach to Active Control

Paper is devoted to problem of acoustical visibility reduction and gives brief description of alternative approach to active control. This approach allows satisfy jointly the four conditions: a) effective suppression of acoustical radiation and scattering caused by elastic body immersed in compressible medium (water); b) cloacking at any important temporal frequencies of ob-servant sound waves; c) cloacking at any important spatial frequencies or at any observation directions; (d) thickness of the masking shell is much smaller than the length of suppressed waves. Technological development gives more and more fast and miniature control elements and fast, accurate calculations. On the other hand, the lengths of waves to be damped are con-stant due to the constant conditions of their far propagation. The approach suggested uses operations of high space-time resolution for long waves controlling. Because the joint fulfillment of the conditions of acoustic support absence and the thinness of the shell and also the causality of control lead to the need to operate at frequencies of much higher than frequencies of waves to be damped. It is assumed that the incident waves are represented by a discrete set of plane waves of finite duration. Also it is assumed only that the characteristic spatial scale of the distribution of normal velocities on the surface of the protected body is limited from below. The boundary value problem with initial conditions is considered.

A Low Cost System for Detecting Fog Events and Triggering an Active Fog Water Collector

A simple method of activating the Caltech Active Strand Cloud-water Collector (CASCC) is described. This system detected the onset of wet deposition events associated with the advection of marine stratus clouds using an optical rain sensor (ORS) and a standard passive fog collector (SFC) in combination with a relative humidity threshold. The system was deployed on a rooftop between May 10 and September 20, 2016 (134 days) at the University of California, Santa Cruz, six km from Pacific Ocean, at 240 m elevation. Twenty-nine fog water samples (daily mean volume = 174 ± 71 mL) were collected for the purposes of quantifying the concentration of monomethylmercury (MMHg) and its possible marine origins. For 20 days during the study, a visibility sensor (VS) was collocated with the ORS and both sensors detected 7 fog events. The ORS detected 2 additional marine stratus drizzle events missed by the VS. The start time of the events detected by the ORS was delayed relative to the onset of visibility reduction in 6 of 7 events by 4.5 ± 3.3 hours. Low wind speeds at night at this location limited the wet deposition to the SFC. Average CASCC sampling time during these events was 6.2 ± 2.8 hours and 4 liquid samples were obtained (80 to > 275 mL). As a comparison, fog water collections at UCSC during the fog seasons of 2014 and 2015 yielded 35 and 12 samples, respectively using a trigger based on relative humidity (RH) and sampling times of > 12 h per day. The main benefit of triggering with the ORS in 2016 was to cut in half the sampling time without loss of sample collection volume. Mean MMHg concentrations between the 3 years were not significantly different suggesting that the SFC/ORS triggering system is appropriate for use at multiple fog collection sites simultaneously.

Development of a Rainfall and Fog Environment Simulator for Non-Contact Safety Related Sensors

In this report, we describe a rainfall and fog environment simulator, which is a test apparatus developed to evaluate the person detection performance of non-contact safety sensors under rainfall and/or fog. This simulator reproduces visibility reduction due to rainfall/fog in a limited indoor space. It consists of a rainfall apparatus, a fog generator, a dripproof linear slider, and some measurement or observation devices. We introduce the structure and specification of the simulator and report the example of the preliminary test results of a range image sensor under the reproduced rainfall.

A Comprehensive Case Study of a Frontal Mineral Dust Storm in spring over Iraq

Dust storms are among the most important weather phenomena in Middle East. The Shamal dust storms are dominated across Iraq and the whole Middle East, especially in summer. However, frontal type of dust storms is possible in winter and spring. In this research, a comprehensive case study was conducted to a dust storm that occurred on 20 March 2016 from many perspectives: synoptic, satellite imagery, dust concentration analysis, visibility reduction, and aerosol optical depth. The study shows that the dust storm initiated inside Syria and moved eastward with the movement of the front. Dust concentrations and aerosol optical depth were also discussed that simulate the dust storm over Iraq in a reasonable way with some differences. The dust concentrations values increase gradually during the early hours of 20 March at 1200 UTC to become within (200-5000) . The dust concentrations comparison with some surrounding countries shows that Iraq had the maximum value at the dust storm time. An experimental relationship to calculate the dust concentration from visibility was tested according to the multi-model products and revealed acceptable estimates. Dust aerosol optical depth offers good means to quantify the dust amount in the Middle East where the dust is the determining factor. Additional investigation was done by using the relative vorticity and the potential vorticity. The results of this investigation show that there are upper shortwaves that are responsible of strengthening of the low pressure system at the surface. The computed value of potential vorticity advection was estimated to be about (2.7×10-4 K m2/kg s) along a distance of about 500 km which suggested a high value of divergence east of the system which lead to a significant updraft.