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Sample records for advection fog formation

  1. Aerosol particles and the formation of advection fog

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Liaw, G. S.; Vaughan, O. H., Jr.

    1979-01-01

    A study of numerical simulation of the effects of concentration, particle size, mass of nuclei, and chemical composition on the dynamics of warm fog formation, particularly the formation of advection fog, is presented. This formation is associated with the aerosol particle characteristics, and both macrophysical and microphysical processes are considered. In the macrophysical model, the evolution of wind components, water vapor content, liquid water content, and potential temperature under the influences of vertical turbulent diffusion, turbulent momentum, and turbulent energy transfers are taken into account. In the microphysical model, the supersaturation effect is incorporated with the surface tension and hygroscopic material solution. It is shown that the aerosol particles with the higher number density, larger size nuclei, the heavier nuclei mass, and the higher ratio of the Van't Hoff factor to the molecular weight favor the formation of the lower visibility advection fogs with stronger vertical energy transfer during the nucleation and condensation time period.

  2. Advection fog formation and aerosols produced by combustion-originated air pollution

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Liaw, G. S.; Vaughan, O. H., Jr.

    1980-01-01

    The way in which pollutants produced by the photochemical reaction of NO(X) and SO(X) affect the quality of the human environment through such phenomena as the formation of advection fog is considered. These pollutants provide the major source of condensation nuclei for the formation of fog in highways, airports and seaports. Results based on the monodisperse, multicomponent aerosol model show that: (1) condensation nuclei can grow and form a dense fog without the air having attained supersaturation; (2) the mass concentration range for NO(X) is one-third that of SO(X); and (3) the greater the mass concentration, the particle concentration, and the radius of condensation nuclei, the denser the fog that is formed.

  3. Hygroscopic chemicals and the formation of advection warm fog: A numerical simulation

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Liaw, G. S.

    1978-01-01

    The formation of advection fog is closely associated with the characteristics of the aerosol particles, including the chemical composition, mass of the nuclei, particle size, and concentration. Both macrophysical and microphysical processes are considered. In the macrophysical model, the evolution of wind components, water vapor content, liquid water content and potential temperature under the influences of vertical turbulent diffusion, turbulent momentum, and turbulent energy transfers are taken into account. In the microphysical model, the supersaturation effect is incorporated with the surface tension and hygroscopic material solution.

  4. Numerical simulation of advection fog formation on multi-disperse aerosols due to combustion-related pollutants

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Liaw, G. S.

    1980-01-01

    The effects of multi-disperse distribution of the aerosol population are presented. Single component and multi-component aerosol species on the condensation/nucleation processes which affect the reduction in visibility are described. The aerosol population with a high particle concentration provided more favorable conditions for the formation of a denser fog than the aerosol population with a greater particle size distribution when the value of the mass concentration of the aerosols was kept constant. The results were used as numerical predictions of fog formation. Two dimensional observations in horizontal and vertical coordinates, together with time-dependent measurements were needed as initial values for the following physical parameters: (1)wind profiles; (2) temperature profiles; (3) humidity profiles; (4) mass concentration of aerosol particles; (5) particle size distribution of aerosols; and (6) chemical composition of aerosols. Formation and dissipation of advection fog, thus, can be forecasted numerically by introducing initial values obtained from the observations.

  5. A Study of the Physical Processes of an Advection Fog Boundary Layer

    NASA Astrophysics Data System (ADS)

    Liu, Duan Yang; Yan, Wen Lian; Yang, Jun; Pu, Mei Juan; Niu, Sheng Jie; Li, Zi Hua

    2016-01-01

    A large quantity of advection fog appeared in the Yangtze River delta region between 1 and 2 December 2009. Here, we detail the fog formation and dissipation processes and the background weather conditions. The fog boundary layer and its formation and dissipation mechanisms have also been analyzed using field data recorded in a northern suburb of Nanjing. The results showed the following: (1) This advection fog was generated by interaction between advection of a north-east cold ground layer and a south-east warm upper layer. The double-inversion structure generated by this interaction between the cold and warm advections and steady south-east vapour transport was the main cause of this long-lasting fog. The double-inversion structure provided good thermal conditions for the thick fog, and the south-east vapour transport was not only conducive to maintaining the thickness of the fog but also sustained its long duration. (2) The fog-top altitude was over 600 m for most of the time, and the fog reduced visibility to less than 100 m for approximately 12 h. (3) The low-level jet near the lower inversion layer also played a role in maintaining the thick fog system by promoting heat, momentum and south-east vapour transport.

  6. Project Fog Drops 5. Task 1: A numerical model of advection fog. Task 2: Recommendations for simplified individual zero-gravity cloud physics experiments

    NASA Technical Reports Server (NTRS)

    Rogers, C. W.; Eadie, W. J.; Katz, U.; Kocmond, W. C.

    1975-01-01

    A two-dimensional numerical model was used to investigate the formation of marine advection fog. The model predicts the evolution of potential temperature, horizontal wind, water vapor content, and liquid water content in a vertical cross section of the atmosphere as determined by vertical turbulent transfer and horizontal advection, as well as radiative cooling and drop sedimentation. The model is designed to simulate the formation, development, or dissipation of advection fog in response to transfer of heat and moisture between the atmosphere and the surface as driven by advection over horizontal discontinuities in the surface temperature. Results from numerical simulations of advection fog formation are discussed with reference to observations of marine fog. A survey of candidate fog or cloud microphysics experiments which might be performed in the low gravity environment of a shuttle-type spacecraft in presented. Recommendations are given for relatively simple experiments which are relevent to fog modification problems.

  7. Examination of the evolution of radiation and advection fogs. Final report

    SciTech Connect

    Orgill, M.M.

    1993-01-01

    A literature study was done on radiation and advection fog evolution. For radiation fog, six stages of fog evolution have been identified -- (1) precursor, (2) sunset, (3) conditioning, (4) mature, (5) sunrise, and (6) dissipation. The evolution of advection fog models has been in parallel with radiation fog models, but no identified stages in the evolution of advection fog have been proposed: (1) precursor, (2) initiation, (3) mature, and (4) dissipation. Radiation and advection fog models will require greater sophistication in order to study fog spatial and temporal variability. Physical aspects that require further study are discussed.

  8. Advective, orographic and radiation fog in the Tarapacá region, Chile

    NASA Astrophysics Data System (ADS)

    Cereceda, P.; Osses, P.; Larrain, H.; Farías, M.; Lagos, M.; Pinto, R.; Schemenauer, R. S.

    A project in northern Chile was undertaken to determine the origin and behaviour of fog in the coastal and inland locations of the Tarapacá Region. In the Pampa del Tamarugal, 50 km from the sea, conditions exist for the formation of radiation fog. Advective fog has been studied on the coast and orographic fog was observed at a few coastal sites near mountain ranges with elevations above 1000 m. Fog water collected by two standard fog collectors (SFC) for 3 1/2 years showed an average flux of 8.5 l m -2 day -1 on the coast and 1.1 l m -2 day -1 inland 12 km from the coastline. On only a few days in 10 months was water collected at the inland site of Pampa del Tamarugal. GOES satellite images are shown to illustrate the pattern of formation of the stratocumuli cloud over the sea, its approach to the coastline, the entrance of fog by corridors through the coastal range and the presence of radiation fog inland. The results are important for the understanding of fog formation and dissipation along the coastal mountain range and for the recognition of potential sites for the installation of fog water collectors, which can be used as a water source in the Atacama Desert. The results also provide vital information for use in the preservation of the unique ecosystems of the most arid desert of the world.

  9. A field study of air flow and turbulent features of advection fog

    NASA Technical Reports Server (NTRS)

    Connell, J. D.

    1979-01-01

    The setup and initial operation of a set of specialized meteorological data collection hardware are described. To study the life cycle of advection fogs at a lake test site, turbulence levels in the fog are identified, and correlated with the temperature gradients and mean wind profiles. A meteorological tower was instrumented to allow multiple-level measurements of wind and temperature on a continuous basis. Additional instrumentation was: (1)hydrothermograph, (2)microbarograph, (3)transmissometers, and (4)a boundary layer profiler. Two types of fogs were identified, and important differences in the turbulence scales were noted.

  10. Fluid mechanics simulation of fog formation associated with polluted atmosphere produced by energy related fuel combustion

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Liaw, G. S.

    1980-01-01

    It is noted that large quantities of atmospheric aerosols with composition SO4(-2), NO3(-1), and NH4(+1) have been detected in highly industrialized areas. Most aerosol products come from energy-related fuel combustion. Fluid mechanics simulation of both microphysical and macrophysical processes is considered in studying the time dependent evolution of the saturation spectra of condensation nuclei associated with polluted and clean atmospheres during the time periods of advection fog formation. The results demonstrate that the condensation nuclei associated with a polluted atmosphere provide more favorable conditions than condensation nuclei associated with a clean atmosphere to produce dense advection fog, and that attaining a certain degree of supersaturation is not necessarily required for the formation of advection fog having condensation nuclei associated with a polluted atmosphere.

  11. Is the Coastal Ocean a Source of Mercury to Marine Advective Fog

    NASA Astrophysics Data System (ADS)

    Heim, W. A.; Weiss-Penzias, P. S.; Fernandez, D.; Byington, A.; Bonnema, A.; Beebe, C.; Chiswell, H.; Olson, A.; Coale, K. H.

    2014-12-01

    Marine advective fog is a common feature along the California coast during the summer season. This fog provides an important water source to many endemic fauna and flora. Studies are underway to better understand the chemical makeup of Pacific marine fog as it is an important input to the hydrologic cycle. We report results from our study focused on investigating the potential for coastal ocean upwelling to contribute volatile organic mercury to the overlying atmosphere where it could be incorporated into cloud droplets as monomethyl mercury (MMHg). Preliminary research by this group has indicated that fog water inputs to certain coastal locations may contribute up to 99% of the MMHg flux to land compared to the MMHg flux in rain. Mercury measurements, including total mercury (Hgt), MMHg, elemental mercury (Hg0), and dimethyl mercury (DMHg), were made to unfiltered water collected from depth profiles at 12 stations from Big Sur to Trinidad Head over the California shelf during summer 2014. Profiles of Hgt ranged from 0.3-2.4 pM and were similar to other reported measurements of Hgt for the North Pacific. A large range in concentration was observed for MMHg (10-540 fM) with elevated values generally occurring below the oxycline (>50m). Concentrations of Hg0 were 0.06 to 0.57 pM with elevated concentrations at depth relative to surface values. Depth profiles of DMHg were similar to MMHg and concentrations were measured from 10-295 fM with highest concentrations observed below the oxycline. Surface concentrations of DMHg averaged 40 ± 22 fM. Given the observed profiles for DMHg and the fact that it is sparingly soluble in water, a net flux of DMHg to the atmosphere is likely occurring. Based on these findings and the fact that MMHg and DMHg concentrations in the coastal ocean were highest in the low oxygen zone, we speculate that mercury is methylated in the water column and/or sediments as DMHg and that this water is upwelled seasonally in the coastal zones and

  12. Marine fog: a review

    USGS Publications Warehouse

    Koračin, Darko; Dorman, Clive E.; Lewis, John M.; Hudson, James G.; Wilcox, Eric M.; Torregrosa, Alicia

    2014-01-01

    The objective of this review is to discuss physical processes over a wide range of spatial scales that govern the formation, evolution, and dissipation of marine fog. We consider marine fog as the collective combination of fog over the open sea along with coastal sea fog and coastal land fog. The review includes a history of sea fog research, field programs, forecasting methods, and detection of sea fog via satellite observations where similarity in radiative properties of fog top and the underlying sea induce further complexity. The main thrust of the study is to provide insight into causality of fog including its initiation, maintenance, and destruction. The interplay between the various physical processes behind the several stages of marine fog is among the most challenging aspects of the problem. An effort is made to identify this interplay between processes that include the microphysics of fog formation and maintenance, the influence of large-scale circulation and precipitation/clouds, radiation, turbulence (air-sea interaction), and advection. The environmental impact of marine fog is also addressed. The study concludes with an assessment of our current knowledge of the phenomenon, our principal areas of ignorance, and future lines of research that hold promise for advances in our understanding.

  13. Predictability of the Meteorological Conditions Favourable to Radiative Fog Formation During the 2011 ParisFog Campaign

    NASA Astrophysics Data System (ADS)

    Menut, Laurent; Mailler, Sylvain; Dupont, Jean-Charles; Haeffelin, Martial; Elias, Thierry

    2013-11-01

    Radiative fog formation is a complex phenomenon involving local physical and microphysical processes that take place when particular meteorological conditions occur. This study aims at quantifying the ability of a regional numerical weather model to analyze and forecast the conditions favourable to radiative fog formation at an instrumental site in the Paris area. Data from the ParisFog campaign have been used in order to quantify the meteorological conditions favorable to radiative fog formation (pre-fog conditions) by setting threshold values on the key meteorological variables driving this process: 2-m temperature tendency, 10-m wind speed, 2-m relative humidity and net infrared flux. Data from the ParisFog observation periods of November 2011 indicate that use of these thresholds leads to the detection of 87 % of cases in which radiative fog formation was observed. In order to evaluate the ability of a regional weather model to reproduce adequately these conditions, the same thresholds are applied to meteorological model fields in both analysis and forecast mode. It is shown that, with this simple methodology, the model detects 74 % of the meteorological conditions finally leading to observed radiative fog, and 48 % 2 days in advance. Finally, sensitivity tests are conducted in order to evaluate the impact of using larger time or space windows on the forecasting skills.

  14. Evidence for fat, oil and grease (FOG) deposit formation mechanisms in sewer lines

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The presence of hardened and insoluble fats, oil, and grease (FOG) deposits in sewer lines is a major cause of line blockages leading to sanitary sewer overflows (SSOs). Despite the central role that FOG deposits play in SSOs, little is known about the mechanisms of FOG deposit formation in sanitary...

  15. Mechanisms of Fat, Oil and Grease (FOG) Deposit Formation in Sewer Lines

    Technology Transfer Automated Retrieval System (TEKTRAN)

    FOG deposits in sewer systems recently have been shown to be metallic salts of fatty acids. However, the fate and transport of FOG deposit reactant constituents and the complex interactions during the FOG deposit formation process are still largely unknown. Batch tests were performed to elucidate ...

  16. Ion Composition of Fog Water and Its Relation to Air Pollutants during Winter Fog Events in Nanjing, China

    NASA Astrophysics Data System (ADS)

    Yang, Jun; Xie, Yu-Jing; Shi, Chun-E.; Liu, Duan-Yang; Niu, Sheng-Jie; Li, Zi-Hua

    2012-05-01

    Intensive field experiments focused on fog chemistry were carried out in the northern suburb of Nanjing during the winters of 2006 and 2007. Thirty-seven fog water samples were collected in nine fog events. Based on the chemical analysis results of those samples and the simultaneous measurements of air pollution gases and atmospheric aerosols, the chemical characteristics of fog water and their relations with air pollutants during fog evolution were investigated. The results revealed an average total inorganic ionic concentration TIC = 21.18 meq/L, and the top three ion concentrations were those of SO4 2-, NH4 + and Ca2+ (average concentrations 6.99, 5.95, 3.77 meq/L, respectively). However, the average pH value of fog water was 5.85, which is attributable to neutralization by basic ions (NH4 + and Ca2+). The average TIC value of fog water measured in advection-radiation fog was around 2.2 times that in radiation fog, and the most abundant cation was NH4 + in advection-radiation fog and Ca2+ in radiation fog. In dense fog episodes, the concentration variations of primary inorganic pollution gases showed a "V"-shaped pattern, while those of volatile organic compounds (VOCs) displayed a "Λ"-shaped pattern. The dense fog acted as both the source and sink of atmospheric aerosol particles; fog processes enhanced particle formation, leading to the phenomenon that the aerosol concentration after fog dissipation was higher than that before the fog, and at the same time, mass concentration of PM10 reached the lowest value in the late stage of extremely dense fog episodes because of the progressive accumulated effect of wet deposition of large fog droplets. Both air pollution gases and aerosols loading controlled the ion compositions of fog water. The Ca2+ in fog water originated from airborne particles, while SO4 2- and NH4 + were from both heterogeneous production and soluble particulate species.

  17. Radiation fog formation alerts using attenuated backscatter power from automatic lidars and ceilometers

    NASA Astrophysics Data System (ADS)

    Haeffelin, Martial; Laffineur, Quentin; Bravo-Aranda, Juan-Antonio; Drouin, Marc-Antoine; Casquero-Vera, Juan-Andrés; Dupont, Jean-Charles; De Backer, Hugo

    2016-11-01

    Radiation fog occurs over many locations around the world in stable atmospheric conditions. Air traffic at busy airports can be significantly disrupted because low visibility at the ground makes it unsafe to take off, land and taxi on the ground. Current numerical weather prediction forecasts are able to predict general conditions favorable for fog formation, but not the exact time or location of fog occurrence. A selected set of observations available in near-real time at strategic locations could also be useful to track the evolution of key processes and key parameters that drive fog formation. Such observations could complement the information predicted by numerical weather prediction (NWP) models that is made available to airport forecasters in support of their fog forecast. This paper presents an experimental setup based on collocated automatic lidar and ceilometer measurements, relative humidity measurements and horizontal visibility measurements to study hygroscopic growth of fog condensation nuclei. This process can take several minutes to hours, and can be tracked using lidar- or ceilometer-attenuated backscatter profiles. Based on hygroscopic growth laws we derive a set of parameters that can be used to provide alerts minutes to hours prior to formation of radiation fog. We present an algorithm that uses the temporal evolution of attenuated backscatter measurements to derive pre-fog formation alerts. The performance of the algorithm is tested on 45 independent pre-fog situations at two locations (near Paris, France, and Brussels, Belgium). We find that an alert for pre-fog conditions predominantly occurs 10-50 min prior to fog formation at an altitude ranging 0 to 100 m above ground. In a few cases, alerts can occur up to 100 min prior to fog formation. Alert durations are found to be sensitive to the relative humidity conditions found a few hours prior to the fog.

  18. Mechanisms of fat, oil and grease (FOG) deposit formation in sewer lines.

    PubMed

    He, Xia; de los Reyes, Francis L; Leming, Michael L; Dean, Lisa O; Lappi, Simon E; Ducoste, Joel J

    2013-09-01

    FOG deposits in sewer systems have recently been shown to be metallic salts of fatty acids. However, the fate and transport of FOG deposit reactant constituents and the complex interactions during the FOG deposit formation process are still largely unknown. In this study, batch tests were performed to elucidate the mechanisms of FOG deposit formation that lead to sanitary sewer overflows (SSOs). We report the first formation of FOG deposits on a concrete surface under laboratory conditions that mimic the formation of deposits in sewer systems. Results showed that calcium, the dominant metal in FOG deposits, can be released from concrete surfaces under low pH conditions and contribute to the formation process. Small amounts of additional oil to grease interceptor effluent substantially facilitated the air/water or pipe surface/water interfacial reaction between free fatty acids and calcium to produce surface FOG deposits. Tests of different fatty acids revealed that more viscous FOG deposit solids were formed on concrete surfaces, and concrete corrosion was accelerated, in the presence of unsaturated FFAs versus saturated FFAs. Based on all the data, a comprehensive model was proposed for the mechanisms of FOG deposit formation in sewer systems.

  19. Fog and Tidal Current Connection at Cape Cod Canal-Early Recognition and Recent Measurements.

    NASA Astrophysics Data System (ADS)

    Woodcock, Alfred H.

    1982-02-01

    Notes by Gardner Emmons about the initiation of low advective fogs on Cape Cod are presented. Subsequent measurements made in these fogs confirm his suggestion that mixing and temperature changes associated with tidal currents account for the fog. Puzzling temperature measurements that are at apparent variance with the mixing theory of fog formation are presented. It is proposed that these temperature discrepancies are due to the effects of water vapor condensation on the sea water surface.

  20. Evidence for fat, oil, and grease (FOG) deposit formation mechanisms in sewer lines.

    PubMed

    He, Xia; Iasmin, Mahbuba; Dean, Lisa O; Lappi, Simon E; Ducoste, Joel J; de los Reyes, Francis L

    2011-05-15

    The presence of hardened and insoluble fats, oil, and grease (FOG) deposits in sewer lines is a major cause of line blockages leading to sanitary sewer overflows (SSOs). Despite the central role that FOG deposits play in SSOs, little is known about the mechanisms of FOG deposit formation in sanitary sewers. In this study, FOG deposits were formed under laboratory conditions from the reaction between free fatty acids and calcium chloride. The calcium and fatty acid profile analysis showed that the laboratory-produced FOG deposit displayed similar characteristics to FOG deposits collected from sanitary sewer lines. Results of FTIR analysis showed that the FOG deposits are metallic salts of fatty acid as revealed by comparisons with FOG deposits collected from sewer lines and pure calcium soaps. Based on the data, we propose that the formation of FOG deposits occurs from the aggregation of excess calcium compressing the double layer of free fatty acid micelles and a saponification reaction between aggregated calcium and free fatty acids.

  1. Factors That Influence Properties of FOG Deposits and Their Formation in Sewer Collection Systems.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding the formation of Fat, Oil, and Grease (FOG) deposits in sewer systems is critical to the sustainability of sewer collection systems since they have been implicated in causing sewerage blockages, which eventually lead to sanitary sewer overflows (SSOs). Recently, FOG deposits in sewer ...

  2. Persistent sulfate formation from London Fog to Chinese haze

    NASA Astrophysics Data System (ADS)

    Wang, Gehui; Zhang, Renyi; Gomez, Mario E.; Yang, Lingxiao; Levy Zamora, Misti; Hu, Min; Lin, Yun; Peng, Jianfei; Guo, Song; Meng, Jingjing; Li, Jianjun; Cheng, Chunlei; Hu, Tafeng; Ren, Yanqin; Wang, Yuesi; Gao, Jian; Cao, Junji; An, Zhisheng; Zhou, Weijian; Li, Guohui; Wang, Jiayuan; Tian, Pengfei; Marrero-Ortiz, Wilmarie; Secrest, Jeremiah; Du, Zhuofei; Zheng, Jing; Shang, Dongjie; Zeng, Limin; Shao, Min; Wang, Weigang; Huang, Yao; Wang, Yuan; Zhu, Yujiao; Li, Yixin; Hu, Jiaxi; Pan, Bowen; Cai, Li; Cheng, Yuting; Ji, Yuemeng; Zhang, Fang; Rosenfeld, Daniel; Liss, Peter S.; Duce, Robert A.; Kolb, Charles E.; Molina, Mario J.

    2016-11-01

    Sulfate aerosols exert profound impacts on human and ecosystem health, weather, and climate, but their formation mechanism remains uncertain. Atmospheric models consistently underpredict sulfate levels under diverse environmental conditions. From atmospheric measurements in two Chinese megacities and complementary laboratory experiments, we show that the aqueous oxidation of SO2 by NO2 is key to efficient sulfate formation but is only feasible under two atmospheric conditions: on fine aerosols with high relative humidity and NH3 neutralization or under cloud conditions. Under polluted environments, this SO2 oxidation process leads to large sulfate production rates and promotes formation of nitrate and organic matter on aqueous particles, exacerbating severe haze development. Effective haze mitigation is achievable by intervening in the sulfate formation process with enforced NH3 and NO2 control measures. In addition to explaining the polluted episodes currently occurring in China and during the 1952 London Fog, this sulfate production mechanism is widespread, and our results suggest a way to tackle this growing problem in China and much of the developing world.

  3. Persistent sulfate formation from London Fog to Chinese haze

    PubMed Central

    Wang, Gehui; Zhang, Renyi; Gomez, Mario E.; Yang, Lingxiao; Levy Zamora, Misti; Hu, Min; Lin, Yun; Peng, Jianfei; Guo, Song; Meng, Jingjing; Li, Jianjun; Cheng, Chunlei; Hu, Tafeng; Ren, Yanqin; Wang, Yuesi; Gao, Jian; Cao, Junji; An, Zhisheng; Zhou, Weijian; Li, Guohui; Wang, Jiayuan; Tian, Pengfei; Marrero-Ortiz, Wilmarie; Secrest, Jeremiah; Du, Zhuofei; Zheng, Jing; Shang, Dongjie; Zeng, Limin; Shao, Min; Wang, Weigang; Huang, Yao; Wang, Yuan; Zhu, Yujiao; Li, Yixin; Hu, Jiaxi; Pan, Bowen; Cai, Li; Cheng, Yuting; Ji, Yuemeng; Zhang, Fang; Rosenfeld, Daniel; Liss, Peter S.; Duce, Robert A.; Kolb, Charles E.; Molina, Mario J.

    2016-01-01

    Sulfate aerosols exert profound impacts on human and ecosystem health, weather, and climate, but their formation mechanism remains uncertain. Atmospheric models consistently underpredict sulfate levels under diverse environmental conditions. From atmospheric measurements in two Chinese megacities and complementary laboratory experiments, we show that the aqueous oxidation of SO2 by NO2 is key to efficient sulfate formation but is only feasible under two atmospheric conditions: on fine aerosols with high relative humidity and NH3 neutralization or under cloud conditions. Under polluted environments, this SO2 oxidation process leads to large sulfate production rates and promotes formation of nitrate and organic matter on aqueous particles, exacerbating severe haze development. Effective haze mitigation is achievable by intervening in the sulfate formation process with enforced NH3 and NO2 control measures. In addition to explaining the polluted episodes currently occurring in China and during the 1952 London Fog, this sulfate production mechanism is widespread, and our results suggest a way to tackle this growing problem in China and much of the developing world. PMID:27849598

  4. On spatiotemporal characteristics of sea fog occurrence over the Northern Atlantic from 1909 to 2008

    NASA Astrophysics Data System (ADS)

    Li, Pengyuan; Wang, Guanlan; Fu, Gang; Lu, Chungu

    2016-12-01

    In this paper, the International Comprehensive Ocean and Atmosphere Data Set (ICOADS) is utilized to investigate the horizontal distribution of sea fog occurrence frequency over the Northern Atlantic as well as the meteorological and oceanic conditions for sea fog formation. Sea fog over the Northern Atlantic mainly occurs over middle and high latitudes. Sea fog occurrence frequency over the western region of the Northern Atlantic is higher than that over the eastern region. The season for sea fog occurrence over the Northern Atlantic is generally from April to August. When sea fogs occur, the prevailing wind direction in the study area is from southerly to southwesterly and the favorable wind speed is around 8 m s-1. It is most favorable for the formation of sea fogs when sea surface temperature (SST) is 5°C to 15°C. When SST is higher than 25°C, it is difficult for the air to get saturated, and there is almost no report of sea fog. When sea fogs form, the difference between sea surface temperature and air temperature is mainly -1 to 3°C, and the difference of 0°C to 2°C is the most favorable conditions for fog formation. There are two types of sea fogs prevailing in this region: advection cooling fog and advection evaporating fog.

  5. A field investigation and numerical simulation of coastal fog

    NASA Technical Reports Server (NTRS)

    Mack, E. J.; Eadie, W. J.; Rogers, C. W.; Kocmond, W. C.; Pilie, R. J.

    1973-01-01

    A field investigation of the microphysical and micrometeorological features of fogs occurring near Los Angeles and Vandenberg, California was conducted. Observations of wind speed and direction, temperature, dew point, vertical wind velocity, dew deposition, drop-size distribution, liquid water content, and haze and cloud nucleus concentration were obtained. These observations were initiated in late evening prior to fog formation and continued until the time of dissipation in both advection and radiation fogs. Data were also acquired in one valley fog and several dense haze situations. The behavior of these parameters prior to and during fog are discussed in detail. A two-dimensional numerical model was developed to investigate the formation and dissipation of advection fogs under the influence of horizontal variations in surface temperature. The model predicts the evolution of potential temperature, water vapor content, and liquid water content in a vertical plane as determined by vertical turbulent transfer and horizontal advection. Results are discussed from preliminary numerical experiments on the formation of warm-air advection fog and dissipation by natural and artificial heating from the surface.

  6. Factors that influence properties of FOG deposits and their formation in sewer collection systems.

    PubMed

    Iasmin, Mahbuba; Dean, Lisa O; Lappi, Simon E; Ducoste, Joel J

    2014-02-01

    Understanding the formation of Fat, Oil, and Grease (FOG) deposits in sewer systems is critical to the sustainability of sewer collection systems since they have been implicated in causing sewerage blockages that leads to sanitary sewer overflows (SSOs). Recently, FOG deposits in sewer systems displayed strong similarities with calcium-based fatty acid salts as a result of a saponification reaction. The objective of this study was to quantify the factors that may affect the formation of FOG deposits and their chemical and rheological properties. These factors included the types of fats used in FSEs, environmental conditions (i.e. pH and temperature), and the source of calcium in sewer systems. The results of this study showed that calcium content in the calcium based salts seemed to depend on the solubility limit of the calcium source and influenced by pH and temperature conditions. The fatty acid profile of the calcium-based fatty acid salts produced under alkali driven hydrolysis were identical to the profile of the fat source and did not match the profile of field FOG deposits, which displayed a high fraction of palmitic, a long chain saturated fatty acid. It is hypothesized that selective microbial metabolism of fats and/or biologically induced hydrogenation may contribute to the FOG deposit makeup in sewer system. Therefore, selective removal of palmitic in pretreatment processes may be necessary prior to the discharge of FSE wastes into the sewer collection system.

  7. Fog climatology in Latvia

    NASA Astrophysics Data System (ADS)

    Avotniece, Zanita; Klavins, Maris; Lizuma, Lita

    2015-10-01

    Fog has been recognised as a hazardous weather phenomenon that can cause accidents and affect urban air quality negatively. Therefore, assessing the characteristics of fog formation, as well as the changes in fog frequency and intensity as a result of climate change is of high importance. This study covers a 52-year period and contains an analysis of the frequency of fog occurring, long-term changes in fog frequency and atmospheric conditions that favour the occurrence of fog events in Latvia. During the analysis, two inter-annual maxima of fog frequency were identified in the spring and autumn; the seasonal differences in the formation of fog were also confirmed using satellite observations of low-level cloudiness. However, the long-term changes of fog frequency showed a decrease tendency of fog to form, which may be associated with improvements in air quality since industrialization and the observed increase of air temperature.

  8. Formation, features and controlling strategies of severe haze-fog pollutions in China.

    PubMed

    Fu, Hongbo; Chen, Jianmin

    2017-02-01

    With rapid industrialization and urbanization, China is facing a great challenge with regard to severe fog-haze pollutions, which were characterized by high fine particulate concentration level and visibility impairment. The control strategies for atmosphere pollutions in China were not only cutting-edge topics of atmospheric research, but also an urgent issue to be addressed by the Chinese government and the public. Focused on the core scientific issues of the haze and fog pollution, this paper reviews the main studies conducted in China, especially after 2010, including formation mechanisms, evolution features, and factors contributing to the fog-haze pollutions. Present policy and control strategies were synoptically discussed. The major challenges ahead will be stated and recommendations for future research directions are proposed at the end of this Review.

  9. Secondary organic aerosol formation through fog processing of VOCs

    NASA Astrophysics Data System (ADS)

    Herckes, P.; Hutchings, J. W.

    2010-07-01

    Volatile Organic Compounds (VOCs) including benzene, toluene, ethylbenzene and xylenes (BTEX) have been determined in highly concentrated amounts (>1 ug/L) in intercepted clouds in northern Arizona (USA). These VOCs are found in concentrations much higher than predicted by partitioning alone. The reactivity of BTEX in the fog/cloud aqueous phase was investigated through laboratory studies. BTEX species showed fast degradation in the aqueous phase in the presence of peroxides and light. Observed half-lives ranged from three and six hours, substantially shorter than the respective gas phase half-lives (several days). The observed reaction rates were on the order of 1 ppb/min but decreased substantially with increasing concentrations of organic matter (TOC). The products of BTEX oxidation reactions were analyzed using HPLC-UV and LCMS. The first generation of products identified included phenol and cresols which correspond to the hydroxyl-addition reaction to benzene and toluene. Upon investigating of multi-generational products, smaller, less volatile species are predominant although a large variety of products is found. Most reaction products have substantially lower vapor pressure and will remain in the particle phase upon droplet evaporation. The SOA generation potential of cloud and fog processing of BTEX was evaluated using simple calculations and showed that in ideal situations these reactions could add up to 9% of the ambient aerosol mass. In more conservative scenarios, the contribution of the processing of BTEX was around 1% of ambient aerosol concentrations. Overall, cloud processing of VOC has the potential to contribute to the atmospheric aerosol mass. However, the contribution will depend upon many factors such as the irradiation, organic matter content in the droplets and droplet lifetime.

  10. Simultaneous fog formation and thermophoretic droplet deposition in a turbulent pipe flow

    SciTech Connect

    Epstein, M.; Hauser, G.M. )

    1991-02-01

    Simultaneous aerosol formation by equilibrium condensation and the migration of the resulting droplets to the cold surface by thermophoresis is studied theoretically for a turbulent pipe flow. The problem is one in which a mixture of a vapor and noncondensable gas flows into a section of pipe where the pipe wall is cooled to below the dew point of the vapor. Because the temperature gradient at the pipe wall decays to zero once the gas travels far enough into the pipe, only some fraction of the droplets formed will deposit on the pipe wall. The equations of energy and diffusion suggest that turbulence leads to a discontinuity in the aerosol (fog) concentration at the boundary between the fog and clear regions. Numerical solutions are obtained for CsOH fog formation and deposition in steam flow, a particular case of current practical interest in water reactor safety. The axial and radial variations of the aerosol and vapor concentrations are displayed graphically, as are the location of the fog boundary as a function of axial distance and the efficiency of deposition as a function of the pipe wall temperature.

  11. The analysis of rapidly developing fog at the Kennedy Space Center

    NASA Technical Reports Server (NTRS)

    Wheeler, Mark M.; Atchison, Michael K.; Schumann, Robin; Taylor, Greg E.; Yersavich, Ann; Warburton, John D.

    1994-01-01

    This report documents fog precursors and fog climatology at Kennedy Space Center (KSC) Florida from 1986 to 1990. The major emphasis of this report focuses on rapidly developing fog events that would affect the less than 7-statute mile visibility rule for End-Of-Mission (EOM) Shuttle landing at KSC (Rule 4-64(A)). The Applied Meteorology Unit's (AMU's) work is to: develop a data base for study of fog associated weather conditions relating to violations of this landing constraint; develop forecast techniques or rules-of-thumb to determine whether or not current conditions are likely to result in an acceptable condition at landing; validate the forecast techniques; and transition techniques to operational use. As part of the analysis the fog events were categorized as either advection, pre-frontal or radiation. As a result of these analyses, the AMU developed a fog climatological data base, identified fog precursors and developed forecaster tools and decision trees. The fog climatological analysis indicates that during the fog season (October to April) there is a higher risk for a visibility violation at KSC during the early morning hours (0700 to 1200 UTC), while 95 percent of all fog events have dissipated by 1600 UTC. A high number of fog events are characterized by a westerly component to the surface wind at KSC (92 percent) and 83 percent of the fog events had fog develop west of KSC first (up to 2 hours). The AMU developed fog decision trees and forecaster tools that would help the forecaster identify fog precursors up to 12 hours in advance. Using the decision trees as process tools ensures the important meteorological data are not overlooked in the forecast process. With these tools and a better understanding of fog formation in the local KSC area, the Shuttle weather support forecaster should be able to give the Launch and Flight Directors a better KSC fog forecast with more confidence.

  12. Numerical forecasting of radiation fog. Part II: A comparison of model simulation with several observed fog events

    SciTech Connect

    Guedalia, D.; Bergot, T. )

    1994-06-01

    A 1D model adapted for forecasting the formation and development of fog, and forced with mesoscale parameters derived from a 3D limited-area model, was used to simulate three fog event observations made during the Lille 88 campaign. The model simulation correctly reproduced the time of fog formation and its vertical development when forcing terms derived from observations were used. It determined the influence of different physical processes and in particular that of dew deposition. The initial conditions deduced from the 3D model proved to be correct in two of the three events. On the other hand, the prediction of advection terms necessary for forecasting the vertical growth of fog was a more delicate matter. 15 refs., 21 figs.

  13. Influence of aerosol spectrum and air pollutants on fog formation in urban environment of megacity Delhi, India.

    PubMed

    Mohan, Manju; Payra, Swagata

    2009-04-01

    Urban areas are facing increasing fog frequencies that may result due to increased air pollution emanating from variety of sources. The increased pollution levels may lead to the atmospheric reactions resulting into the formation of secondary pollutants that may also lead to increased aerosol number concentrations (ANC) in the atmosphere. This could cause enhanced water aerosols in the presence of favourable meteorological conditions and high relative humidity. This study deals with the atmospheric pollution and visibility during winter season of megacity Delhi in order to assess the relationship between the two specifically during fog episodes. Thus, this study analyses the levels of air pollutants, aerosol spectrum and meteorological conditions during one week each in the winter season of the years 2004 and 2006 in order to have an improved understanding of their role in fog formation in mega-city Delhi. More than 300 h of measurements which included episodes of dense, thick and moderate fogs of about 25 h, were studied. The measurements cover most of the accumulation mode and greater size spectrum of aerosols. Thus, the analysis is performed for the entire period, specifically, before the fog sets up, during and afterwards. In general, the relatively small variations in number concentration show larger variations in visibility prior and post dense fog formation than during dense fog episodes. Preliminary analysis of monthly averaged RSPM (Respirable Suspended particulate Matter or PM(10)) concentration values for four winter months for a period of 6 years (1996-2001) and visibility did not show a good correlation with total occurrences of fog. However, daily averaged RSPM concentration showed a good correlation with the occurrences of thick fog. Diurnal variation of Sulfur-dioxide and Nitrogen dioxide were found to have inverse relationship with visibility during fog which may be due to formation of secondary pollutants such as sulfate and to a lesser extent

  14. Freezing Fog Formation in a Supercooled Boundary Layer: Solving the Winter Fog Forecasting Challenge for Elmendorf Air Force Base, Alaska

    DTIC Science & Technology

    2007-03-01

    vicinity of the base are a wide variety of streams, small lakes and tundra , with large trees along some streams in the valley. The largest stream in the...and dry cA air mass move in from 15 the northwest associated with a Siberian High, while a much warmer and moister mP air mass would move in from...a Siberian High and a Gulf of Alaska Low at the start of the fog event. The low pressure center was nearly 400NM southeast of the base with an

  15. Extreme haze pollution in Beijing during January 2013: chemical characteristics, formation mechanism and role of fog processing

    NASA Astrophysics Data System (ADS)

    Huang, K.; Zhuang, G.; Wang, Q.; Fu, J. S.; Lin, Y.; Liu, T.; Han, L.; Deng, C.

    2014-03-01

    Severe haze hovered over large areas of China in January 2013 right after the public release of PM2.5 data of major cities in China at the very first time. This historical severe haze emerged over the northern China with monthly average concentrations of PM2.5, SO2, and NO2 exceeding 225, 200, and 80 μg m-3, respectively. Surface aerosol mean concentration of Beijing in January 2013 reached record high (only slightly lower than 2006) compared to historical data from 2003-2012, but with the largest daily fluctuation. Anomalous meteorological conditions in 2013 compared to the mean climatology from 2007-2012 were especially favorable for the formation of haze, such as higher humidity, lower temperature, lower PBL height, lower wind speed, and the high frequency of fog occurrences. The field campaign in Beijing showed an extremely high PM2.5 average concentration of 299.2 ± 79.1μg m-3 with extremely low visibility of 0.92 ± 0.82 km during an episode of high relative humidity with fog events. High AOD (Aerosol Optical Depth) was observed during fog days but with relatively low Angstrom exponent (< 1.0), suggesting the modification of fog processing on the particle size. Major aerosol chemical species, such as SO42-, NO3-, NH4+, Cl-, K+, and C2O42- presented an explicit exponential growth relationship with relative humidity, suggesting the significant impact of aerosol hygroscopicity on the visibility impairment. SO42- increased ∼5 folds while NO3-, NH4+, and C2O42- increased ∼3 folds in the fog days compared to the non-fog days. Aerosol in fog days was much more acidic than that in non-fog days. The in situ aerosol pH ranged from -0.78 to 0.14 in fog days based on the E-AIM model simulation. Bisulfate (HSO42-) accounted for 52% of the total sulfate and free hydrogen ion (H+Aq) accounted for 27% of the total acids in average. Enhanced coal combustion during the winter heating season along with traffic and industrial emissions were recognized to be the major

  16. Implementation of warm-cloud processes in a source-oriented WRF/Chem model to study the effect of aerosol mixing state on fog formation in the Central Valley of California

    NASA Astrophysics Data System (ADS)

    Lee, H.-H.; Chen, S.-H.; Kleeman, M. J.; Zhang, H.; DeNero, S. P.; Joe, D. K.

    2015-11-01

    The source-oriented Weather Research and Forecasting chemistry model (SOWC) was modified to include warm cloud processes and applied to investigate how aerosol mixing states influence fog formation and optical properties in the atmosphere. SOWC tracks a 6-dimensional chemical variable (X, Z, Y, Size Bins, Source Types, Species) through an explicit simulation of atmospheric chemistry and physics. A source-oriented cloud condensation nuclei module was implemented into the SOWC model to simulate warm clouds using the modified two-moment Purdue Lin microphysics scheme. The Goddard shortwave and longwave radiation schemes were modified to interact with source-oriented aerosols and cloud droplets so that aerosol direct and indirect effects could be studied. The enhanced SOWC model was applied to study a fog event that occurred on 17 January 2011, in the Central Valley of California. Tule fog occurred because an atmospheric river effectively advected high moisture into the Central Valley and nighttime drainage flow brought cold air from mountains into the valley. The SOWC model produced reasonable liquid water path, spatial distribution and duration of fog events. The inclusion of aerosol-radiation interaction only slightly modified simulation results since cloud optical thickness dominated the radiation budget in fog events. The source-oriented mixture representation of particles reduced cloud droplet number relative to the internal mixture approach that artificially coats hydrophobic particles with hygroscopic components. The fraction of aerosols activating into CCN at a supersaturation of 0.5 % in the Central Valley decreased from 94 % in the internal mixture model to 80 % in the source-oriented model. This increased surface energy flux by 3-5 W m-2 and surface temperature by as much as 0.25 K in the daytime.

  17. Implementation of warm-cloud processes in a source-oriented WRF/Chem model to study the effect of aerosol mixing state on fog formation in the Central Valley of California

    NASA Astrophysics Data System (ADS)

    Lee, Hsiang-He; Chen, Shu-Hua; Kleeman, Michael J.; Zhang, Hongliang; DeNero, Steven P.; Joe, David K.

    2016-07-01

    The source-oriented Weather Research and Forecasting chemistry model (SOWC) was modified to include warm cloud processes and was applied to investigate how aerosol mixing states influence fog formation and optical properties in the atmosphere. SOWC tracks a 6-D chemical variable (X, Z, Y, size bins, source types, species) through an explicit simulation of atmospheric chemistry and physics. A source-oriented cloud condensation nuclei module was implemented into the SOWC model to simulate warm clouds using the modified two-moment Purdue Lin microphysics scheme. The Goddard shortwave and long-wave radiation schemes were modified to interact with source-oriented aerosols and cloud droplets so that aerosol direct and indirect effects could be studied. The enhanced SOWC model was applied to study a fog event that occurred on 17 January 2011, in the Central Valley of California. Tule fog occurred because an atmospheric river effectively advected high moisture into the Central Valley and nighttime drainage flow brought cold air from mountains into the valley. The SOWC model produced reasonable liquid water path, spatial distribution and duration of fog events. The inclusion of aerosol-radiation interaction only slightly modified simulation results since cloud optical thickness dominated the radiation budget in fog events. The source-oriented mixture representation of particles reduced cloud droplet number relative to the internal mixture approach that artificially coats hydrophobic particles with hygroscopic components. The fraction of aerosols activating into cloud condensation nuclei (CCN) at a supersaturation of 0.5 % in the Central Valley decreased from 94 % in the internal mixture model to 80 % in the source-oriented model. This increased surface energy flux by 3-5 W m-2 and surface temperature by as much as 0.25 K in the daytime.

  18. Self-organization and advective transport in the cell polarity formation for asymmetric cell division.

    PubMed

    Seirin Lee, Sungrim; Shibata, Tatsuo

    2015-10-07

    Anterior-Posterior (AP) polarity formation of cell membrane proteins plays a crucial role in determining cell asymmetry, which depends not only on the several genetic process but also biochemical and biophysical interactions. The mechanism of AP formation of Caenorhabditis elegans embryo is characterized into the three processes: (i) membrane association and dissociation of posterior and anterior proteins, (ii) diffusion into the membrane and cytosol, and (iii) active cortical and cytoplasmic flows induced by the contraction of the acto-myosin cortex. We explored the mechanism of symmetry breaking and AP polarity formation using self-recruitment model of posterior proteins. We found that the AP polarity pattern is established over wide range in the total mass of polarity proteins and the diffusion ratio in the cytosol to the membrane. We also showed that the advective transport in both membrane and cytosol during the establishment phase affects optimal time interval of establishment and positioning of the posterior domain, and plays a role to increase the robustness in the AP polarity formation by reducing the number of posterior domains for the sensitivity of initial conditions. We also demonstrated that a proper ratio of the total mass to cell size robustly regulate the length scale of the posterior domain.

  19. An Overview of the MATERHORN Fog Project: Observations and Predictability

    NASA Astrophysics Data System (ADS)

    Gultepe, I.; Fernando, H. J. S.; Pardyjak, E. R.; Hoch, S. W.; Silver, Z.; Creegan, E.; Leo, L. S.; Pu, Zhaoxia; De Wekker, S. F. J.; Hang, Chaoxun

    2016-09-01

    A field campaign design to study fog processes in complex terrain was a component of the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program. The experiment was conducted in the Wasatch Mountains during January 5-February 15, 2015. Fog and in particular, Ice fog (IF), defined as fog composed of only ice crystals, was studied during a part of the campaign, and this component of the program was dubbed MATERHORN-Fog. Ice fog often occurs in mountainous regions due do rapid cooling, such as radiative cooling, advective cooling, and cooling associated with mountain circulations (e.g., slope and valley winds). A variety of major instrument platforms were deployed, which included meteorological towers, a SODAR, a LiDAR, ceilometers, and a tethersonde profiler. In addition, in situ measurements took place at several locations surrounding Salt Lake City and Heber City. During the campaign, ice fog occurred at temperatures below -5 °C down to -13 °C and lasted for several hours until radiative heating became significant. The visibility (Vis) during ice fog events ranged from 100 m up to 10 km. At the Heber City site an array of sensors for measuring microphysical, radiative, and dynamical characteristics of IF events were deployed. Some local effects such as upslope advection were observed to affect the IF conditions. As expected during these events, ice water content (IWC) varied from 0.01 up to 0.2 g m-3, with radiative cooling fluxes as strong as 200 W m-2; turbulent heat and moisture fluxes were significantly lower during fog events than those of fog dissipation. At times, the measured ice crystal number concentration was as high as 100 cm-3 during periods of saturation with respect to ice. N i was not a constant as usually assumed in forecasting simulations, but rather changed with increasing IWC. Measurement based statistics suggested that the occurrence of IF events in the region was up to 30 % during the study period in the winter of 2015

  20. A Fog Climatology for Cape Town International Airport

    NASA Astrophysics Data System (ADS)

    van Schalkwyk, L.; Dyson, L. L.

    2010-07-01

    Cape Town International Airport (CTIA) is situated off the cold Benguela current on the extreme southern side of the west coast of South Africa and experiences fog more frequently than any other international airport in South Africa. The aim of this research is ultimately to improve fog forecasts and to determine the characteristics of fog at CTIA by means of a comprehensive fog climatology. A fog climatology is derived making use of 06:00Z observations over a period of 31 years (1978-2008). The fog season for CTIA is observed to start in March and persists till August, while May is found to be the month with the highest frequency of fog events. Analysis of advection and radiation fog events shows that the occurrence of advection fog events dominate during the earlier part of the fog season, whilst radiation fog occurrences increase towards the latter part. Advection fog events at CTIA have been shown to occur frequently from a northwesterly and a southerly wind direction, but monthly wind roses for CTIA at 06:00Z show that a northeasterly wind (land breeze) is dominant during advection events in July and August. This suggests a third type of fog event, namely advected radiation fog, which accounts for fog that forms due to radiative processes to the east and northeast of the aerodrome, where after it is advected towards the airport when the land breeze is at its strongest prior to sunrise. The climatology is supplemented by an analysis of hourly data which are available for the limited period of 2004-2007. With the aid of hourly data, more accurate estimations of the average time of onset and dissipation of fog are determined as well as duration time: information critical to the aviation forecaster.

  1. Diagnosing Antarctic Fog

    NASA Astrophysics Data System (ADS)

    Lazzara, M. A.

    2010-07-01

    Fog affects aviation and other logistical operations in the Antarctic; nevertheless limited studies have been conducted to understand fog behavior in this part of the world. A study has been conducted in the Ross Island region of Antarctica, the location of McMurdo Station and Scott Base - the main stations of the United States and New Zealand Antarctic programs, respectively. Using tools such as multi-channel satellites observations and supported by in situ radiosonde and ground-based automatic weather station observations, combined with back trajectory and mesoscale numerical models, discover that austral summer fog events are "advective" in temperament. The diagnosis finds a primary source region from the southeast over the Ross Ice Shelf (over 72% of the cases studied) while a minority of cases point toward a secondary fog source region to the north along the Scott Coast of the Ross Sea with influences from the East Antarctic Plateau. Part of this examination confirms existing anecdotes from forecasters and weather observers, while refuting others about fog and its behavior in this environment. This effort marks the beginning of our understanding of Antarctic fog behavior.

  2. F-O-G Ring Formation in Glycopeptide Antibiotic Biosynthesis is Catalysed by OxyE

    PubMed Central

    Peschke, Madeleine; Brieke, Clara; Cryle, Max J.

    2016-01-01

    The glycopeptide antibiotics are peptide-based natural products with impressive antibiotic function that derives from their unique three-dimensional structure. Biosynthesis of the glycopeptide antibiotics centres of the combination of peptide synthesis, mediated by a non-ribosomal peptide synthetase, and the crosslinking of aromatic side chains of the peptide, mediated by the action of a cascade of Cytochrome P450s. Here, we report the first example of in vitro activity of OxyE, which catalyses the F-O-G ring formation reaction in teicoplanin biosynthesis. OxyE was found to only act after an initial C-O-D crosslink is installed by OxyB and to require an interaction with the unique NRPS domain from glycopeptide antibiotic – the X-domain – in order to display catalytic activity. We could demonstrate that OxyE displays limited stereoselectivity for the peptide, which mirrors the results from OxyB-catalysed turnover and is in sharp contrast to OxyA. Furthermore, we show that activity of a three-enzyme cascade (OxyB/OxyA/OxyE) in generating tricyclic glycopeptide antibiotic peptides depends upon the order of addition of the OxyA and OxyE enzymes to the reaction. This work demonstrates that complex enzymatic cascades from glycopeptide antibiotic biosynthesis can be reconstituted in vitro and provides new insights into the biosynthesis of these important antibiotics. PMID:27752135

  3. New Particle Formation in Anthropogenic Plumes Advecting from Asia Observed During TRACE-P

    NASA Technical Reports Server (NTRS)

    Weber, R. J.; Lee, S.; Chen, G.; Wang, B.; Kapustin, V.; Moore, K.; Clarke, A. D.; Mauldin, L.; Kosciuch, E.; Cantrell, C.

    2003-01-01

    The characteristics and sources of what are believed to be newly formed 3 to 4 nm particles in anthropogenic plumes advecting from Asian are reported. Airborne measurements were made from March to April 2001 as part of the NASA TRACE-P experiment at latitudes ranging from North of the Philippines to Northern Japan (20 to 45 deg. N). In the more polluted plumes, high concentrations of 3 to 4 nm diameter particles (less than 100/qu cm) were observed both within and along the upper outer edges of plumes that were identified by enhanced carbon monoxide and fine particulate sulfate concentrations. The results from two research flights are investigated in detail. Three to four-nm particle concentrations are generally correlated with gas phase sulfuric acid and found in regions of low surface areas relative to the immediate surroundings or where there are steep transitions to lower surface areas. Sulfuric acid and surface area concentrations in the most polluted plume reached 6 x l0(exp 7) and 750 micro sq m/qu cm, respectively, in regions of particle formation. In contrast to these anthropogenic plumes, few 3 to 4 nm particles were observed in the clean background and few were detected within a volcanic plume where the studies highest H2SO4 concentrations (less than lO(exp 8)/qu cm) were recorded. Enhanced SO2 concentrations in the range of approximately 2 to 7 ppb, in conjunction with other unidentified, possibly coemitted species, appear to be the driving factor for nucleation. (0345, 4801); 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0345 Atmospheric Composition and Structure: Pollution-urban and regional (0305); 4801 Oceanography: Biological and Chemical: Aerosols (0305).

  4. A Case Study of the Mechanisms Modulating the Evolution of Valley Fog

    NASA Astrophysics Data System (ADS)

    Hang, C.; Nadeau, D. F.; Gultepe, I.; Hoch, S. W.; Román-Cascón, C.; Pryor, K.; Fernando, H. J. S.; Creegan, E. D.; Leo, L. S.; Silver, Z.; Pardyjak, E. R.

    2016-09-01

    We present a valley fog case study in which radiation fog is modulated by topographic effects using data obtained from a field campaign conducted in Heber Valley, Utah from January 7-February 1, 2015, as part of the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) program. We use data collected on January 9, 2015 to gain insight into relationships between typical shallow radiation fog, turbulence, and gravity waves associated with the surrounding topography. A ≈ 10-30 m fog layer formed by radiative cooling was observed from 0720 to 0900 MST under cold air temperatures (≈-9 °C), near-saturated (relative humidity with respect to water ≈95 %), and calm wind (mostly <0.5 m s-1) conditions. Drainage flows were observed occasionally prior to fog formation, which modulated heat exchanges between air masses through the action of internal gravity waves and cold-air pool sloshing. The fog appeared to be triggered by cold-air advection from the south (≈200°) at 0700 MST. Quasi-periodic oscillations were observed before and during the fog event with a time period of about 15 min. These oscillations were detected in surface pressure, temperature, sensible heat flux, incoming longwave radiation, and turbulent kinetic energy measurements. We hypothesize that the quasi-periodic oscillations were caused by atmospheric gravity waves with a time period of about 10-20 min based on wavelet analysis. During the fog event, internal gravity waves led to about 1 °C fluctuations in air temperatures. After 0835 MST when net radiation became positive, fog started to dissipate due to the surface heating and heat absorption by the fog particles. Overall, this case study provides a concrete example of how fog evolution is modulated by very weak thermal circulations in mountainous terrain and illustrates the need for high density vertical and horizontal measurements to ensure that the highly spatially varying physics in complex terrain are sufficient for hypothesis

  5. A study on transition of stratus cloud into sea fog over the Yellow Sea near the Korean Peninsula

    NASA Astrophysics Data System (ADS)

    Kim, C.; Yum, S. S.; Song, Y.

    2011-12-01

    Sea fog is still the difficult issue in the numerical weather prediction even if the computation power as well as the parameterization of physics and dynamic for numerical modeling has been developed during past several decades. Numerical weather prediction for the evolution of sea fog requires the vertical high resolution and the sophisticated physics including cloud formation, turbulence and radiation. This study tries to couple 1D turbulence model with 3D regional model to solve the intrinsic deficiency of 3D regional model in terms of vertical resolution. In general, 1D turbulence model employs the vertical resolution to resolve turbulence structure within planetary boundary layer. However, horizontal advections of heat and moisture and large scale subsidence are not predicted by 1D turbulence model and therefore they should be parameterized by 3D regional model output. This study uses Parameterized FOG (PAFOG) model as 1D turbulence model and Weather Research and Forecast (WRF) as 3D regional model. In winter season, sea fog is formed over the Yellow Sea near the Korean Peninsula relatively rarely, compared with summer season. Nine of sea fogs are observed from 2002 to 2006. Prior to the formation of sea fog in winter season, stratus cloud is observed. It may imply that stratus is related to the formation of sea fog in winter season. This study tries to identify the transition mechanism of stratus into sea fog over the Yellow Sea using numerical simulation. Preliminarily, numerical simulation results in the formation of stratus within convective boundary layer, prior to the formation of sea fog. This stratus cloud is lowered into the sea surface and then sea fog is formed over the Yellow Sea near the Korean Peninsula. The lowering process of stratus cloud into the sea surface is related to turbulent effect on the bottom of stratus cloud and large scale subsidence on the stratus top. A detailed characteristic of the lowering process will be presented in the

  6. Analysis and high-resolution modeling of a dense sea fog event over the Yellow Sea

    NASA Astrophysics Data System (ADS)

    Fu, Gang; Guo, Jingtian; Xie, Shang-Ping; Duan, Yihong; Zhang, Meigen

    2006-10-01

    A ubiquitous feature of the Yellow Sea (YS) is the frequent occurrence of the sea fog in spring and summer season. An extremely dense sea fog event was observed around the Shandong Peninsula in the morning of 11 April 2004. This fog patch, with a spatial scale of several hundreds kilometers and lasted about 20 h, reduced the horizontal visibility to be less than 20 m in some locations, and caused a series of traffic collisions and 12 injuries on the coastal stretch of a major highway. In this paper, almost all available observational data, including Geostationary Operational Environmental Satellite (GOES)-9 visible satellite imagery, objectively reanalyzed data of final run analysis (FNL) issued by the National Center for Environmental Prediction (NCEP) and the sounding data of Qingdao and Dalian, as well as the latest 4.4 version of Regional Atmospheric Modeling System (RAMS) model, were employed to investigate this sea fog case. Its evolutionary process and the environmental conditions that led to the fog formation were examined by using GOES-9 visible satellite imagery and sounding observations. In order to better understand the fog formation mechanism, a high-resolution RAMS modeling of 4 km × 4 km was designed. The modeling was initialized and validated by FNL data. A 30-h modeling that started from 18 UTC 10 April 2004 reproduced the main characteristics of this fog event. The simulated lower horizontal visibility area agreed reasonably well with the sea fog region identified from the satellite imagery. Advection cooling effect seemed to play a significant role for the fog formation.

  7. Modeling Radiation Fog

    NASA Astrophysics Data System (ADS)

    K R, Sreenivas; Mohammad, Rafiuddin

    2016-11-01

    Predicting the fog-onset, its growth and dissipation helps in managing airports and other modes of transport. After sunset, occurrence of fog requires moist air, low wind and clear-sky conditions. Under these circumstances radiative heat transfer plays a vital role in the NBL. Locally, initiation of fog happens when the air temperature falls below the dew-point. Thus, to predict the onset of fog at a given location, one has to compute evolution of vertical temperature profile. Earlier,our group has shown that the presence of aerosols and vertical variation in their number density determines the radiative-cooling and hence development of vertical temperature profile. Aerosols, through radiation in the window-band, provides an efficient path for air layers to lose heat to the cold, upper atmosphere. This process creates cooler air layer between warmer ground and upper air layers and resulting temperature profile facilitate the initiation of fog. Our results clearly indicates that accounting for the presence of aerosols and their radiative-transfer is important in modeling micro-meteorological process of fog formation and its evolution. DST, Govt. INDIA.

  8. An advective mechanism for deep chlorophyll maxima formation in southern Drake Passage

    NASA Astrophysics Data System (ADS)

    Erickson, Zachary K.; Thompson, Andrew F.; Cassar, Nicolas; Sprintall, Janet; Mazloff, Matthew R.

    2016-10-01

    We observe surface and subsurface fluorescence-derived chlorophyll maxima in southern Drake Passage during austral summer. Backscatter measurements indicate that the deep chlorophyll maxima (DCMs) are also deep biomass maxima, and euphotic depth estimates show that they lie below the euphotic layer. Subsurface, offshore and near-surface, onshore features lie along the same isopycnal, suggesting advective generation of DCMs. Temperature measurements indicate a warming of surface waters throughout austral summer, capping the winter water (WW) layer and increasing off-shelf stratification in this isopycnal layer. The outcrop position of the WW isopycnal layer shifts onshore, into a surface phytoplankton bloom. A lateral potential vorticity (PV) gradient develops, such that a down-gradient PV flux is consistent with offshore, along-isopycnal tracer transport. Model results are consistent with this mechanism. Subduction of chlorophyll and biomass along isopycnals represents a biological term not observed by surface satellite measurements which may contribute significantly to the strength of the biological pump in this region.

  9. Project Fog Drops. Part 1: Investigations of warm fog properties

    NASA Technical Reports Server (NTRS)

    Pilie, R. J.; Eadie, W.; Mack, E. J.; Rogers, C.; Kocmond, W. C.

    1972-01-01

    A detailed study was made of the micrometeorological and microphysical characteristics of eleven valley fogs occurring near Elmira, New York. Observations were made of temperature, dew point, wind speed and direction, dew deposition, vertical wind velocity, and net radiative flux. In fog, visibility was continuously recorded and periodic measurements were made of liquid water content and drop-size distribution. The observations were initiated in late evening and continued until the time of fog dissipation. The vertical distribution of temperature in the lowest 300 meters and cloud nucleus concentration at several heights were measured from an aircraft before fog nucleus concentrations at several heights were measured from an aircraft before fog formation. A numerical model was developed to investigate the life cycle of radiation fogs. The model predicts the temporal evolution of the vertical distributions of temperature, water vapor, and liquid water as determined by the turbulent transfer of heat and moisture. The model includes the nocturnal cooling of the earth's surface, dew formation, fog drop sedimentation, and the absorption of infrared radiation by fog.

  10. Fog dispersion

    NASA Technical Reports Server (NTRS)

    Frost, W.; Christensen, L. S.; Collins, F. G.; Camp, D. W.

    1980-01-01

    A study of economically viable techniques for dispersing warm fog at commercial airports is presented. Five fog dispersion techniques are examined: evaporation suppression, downwash, mixing, seeding with hygroscopic material, thermal techniques, and charged particle techniques. Thermal techniques, although effective, were found to be too expensive for routine airport operations, and detrimental to the environment. Seeding or helicopter downwash are practical for small-scale or temporary fog clearing, but are probably not useful for airport operations on a routine basis. Considerable disagreement exists on the capability of charged particle techniques, which stems from the fact that different assumptions and parameter values are used in the analytical models. Recommendations resulting from the review of this technique are listed, and include: experimental measurements of the parameters in question; a study to ascertain possible safety hazards, such as increased electrical activity or fuel ignition during refueling operations which could render charged particle techniques impractical; and a study of a single charged particle generator.

  11. Acid fog

    SciTech Connect

    Hileman, B.

    1983-03-01

    Fog in areas of southern California previously thought to be pollution-free has been shown to have a pH as low as 1.69. It has been found to be most acidic after smoggy days, suggesting that it forms on the aerosol associated with the previously exiting smog. Studies on Whiteface Mountain in the Adirondacks show that fog water is often 10 times as acidic as rainwater. As a result of their studies, California plans to spend $4 million on acid deposition research in the coming year. (JMT)

  12. Partitioning the relative contribution of dew and fog to total occult precipitation across a decreasing fog inundation gradient in the Pajaro Valley, CA

    NASA Astrophysics Data System (ADS)

    Farlin, J. P.; Paw U, K. T.

    2015-12-01

    Traditionally, occult precipitation has been difficult to measure, especially given that it can take two predominant forms: fogs and dews. Recent studies have shown that estimates of fog deposition can be made using constructed fog collectors of various styles. Leaf-wetness sensors have also been deployed to try and estimate the relative wetness of leaves during fog events, but coastal systems can integrate both fog deposition and dew condensation, which cannot be differentiated with such sensors alone. We measured fog interception with Decagon Leaf Wetness Sensors (LWSs) outfitted with a 1m2 mesh passive fog collector in areas adjacent to the California Irrigation Management Information System (CIMIS) sites in the Pajaro Valley. The LWSs that were deployed were covered with a partial shield or left uncovered. Covering the LWS creates a microclimate that allows discrimination between fog events that horizontally advect droplets that impact individual leaves, and dew events, which condense once dew point temperature is reached. By measuring fog with a standard measurement device (mesh fog collector), and comparing it to LWSs that have either fog exposure or fog exclusion (covered LWSs), we can partition the relative contribution of dew to overall occult precipitation. This would be the first study quantifying the amount of water inputs (horizontally advecting fog) to the amount of recycled water (dew) to gain a greater understanding of the role of occult precipitation in catchment water balances across coastal California.

  13. Evidence for photochemical formation of H[sub 2]O[sub 2] and oxidation of SO[sub 2] in authentic fog water

    SciTech Connect

    Yuegang Zuo, Hoigne, J. )

    1993-04-02

    When samples of rain and fog water were exposed to ultraviolet and visible light, reactive transients such as hydrogen peroxide were formed and dissolved organic matter and sulfur dioxide were depleated. These results, in conjunction with those from previous studies, imply that dissolved organic compounds and transition metals such as iron ions are involved in the photochemical formation of hydrogen peroxide and other photooxidants in atmospheric waters.

  14. Acid-fog deposition at Kilauea volcano: A possible mechanism for the formation of siliceous-sulfate rock coatings on Mars

    NASA Astrophysics Data System (ADS)

    Schiffman, Peter; Zierenberg, Robert; Marks, Naomi; Bishop, Janice L.; Darby Dyar, M.

    2006-11-01

    On the summit of Kilauea volcano, sulfur dioxide, which is continuously emitted from Halemaumau crater and rapidly sequestered into sulfuric-acid rich aerosol entrained in the prevailing trade winds, is subsequently precipitated as acid fog immediately downwind from Kilauea caldera in the Kau Desert. The characteristic pH of surface tephra deposits is <4.0 in Sand Wash, a region of nearly continuous, acidic aerosol fallout immediately southwest of the caldera. Vertical exposures of unconsolidated tephras of the Keanakakoi Ash found within fissures and small, dry gullies are coated with thin rock coatings of amorphous silica and jarosite. These rock coatings are formed via an evaporative mechanism whereby acidic pore fluids, circulating in the upper few meters within the highly porous tephra, are wicked toward the walls of the gullies. Geochemical modeling of the rock coating formation process implies that the sulfate formation via evaporation occurs subsequent to minimal interaction of acidic pore fluids with the basaltic tephra. This also suggests that the cycle from acid-fog fallout to precipitation of the siliceous-sulfate rock coatings must occur quite rapidly. Acid-fog deposition of sulfate and silica at Kilauea may provide one mechanism for the origin of jarosite-bearing outcrops on Mars.

  15. Sulfate Formation Enhanced by a Cocktail of High NOx, SO2, Particulate Matter, and Droplet pH during Haze-Fog Events in Megacities in China: An Observation-Based Modeling Investigation.

    PubMed

    Xue, Jian; Yuan, Zibing; Griffith, Stephen M; Yu, Xin; Lau, Alexis K H; Yu, Jian Zhen

    2016-07-19

    In recent years in a few Chinese megacities, fog events lasting one to a few days have been frequently associated with high levels of aerosol loading characterized by high sulfate (as high as 30 μg m(-3)), therefore termed as haze-fog events. The concomitant pollution characteristics include high gas-phase mixing ratios of SO2 (up to 71 ppbv) and NO2 (up to 69 ppbv), high aqueous phase pH (5-6), and smaller fog droplets (as low as 2 μm), resulting from intense emissions from fossil fuel combustion and construction activities supplying abundant Ca(2+). In this work, we use an observation-based model for secondary inorganic aerosols (OBM-SIA) to simulate sulfate formation pathways under conditions of haze-fog events encountered in Chinese megacities. The OBM analysis has identified, at a typical haze-fogwater pH of 5.6, the most important pathway to be oxidation of S(IV) by dissolved NO2, followed by the heterogeneous reaction of SO2 on the aerosol surface. The aqueous phase oxidation of S(IV) by H2O2 is a very minor formation pathway as a result of the high NOx conditions suppressing H2O2 formation. The model results indicate that the unique cocktail of high fogwater pH, high concentrations of NO2, SO2, and PM, and small fog droplets are capable of greatly enhancing sulfate formation. Such haze-fog conditions could lead to rapid sulfate production at night and subsequently high PM2.5 in the morning when the fog evaporates. Sulfate formation is simulated to be highly sensitive to fogwater pH, PM, and precursor gases NO2 and SO2. Such insights on major contributing factors imply that reduction of road dust and NOx emissions could lessen PM2.5 loadings in Chinese megacities during fog events.

  16. Chemical composition of fog water in Nanjing area of China and its related fog microphysics

    NASA Astrophysics Data System (ADS)

    Lu, Chunsong; Niu, Shengjie; Tang, Lili; Lv, Jingjing; Zhao, Lijuan; Zhu, Bin

    2010-07-01

    Fog samples were collected at Pancheng in the Nanjing area of China during December 2006 and December 2007. Fog droplet spectra, surface meteorological elements and visibility were also measured during the same period. The data from PM 10, SO 2 and NO 2 measurements were obtained from the air quality monitoring networks of Nanjing. The total ionic concentration (TIC) and electrical conductivity (EC) in fog samples, and the local pollutant emissions were one or two orders of magnitude higher than those found in Europe or South America for instance. Pollutants were expected to be mainly from local sources, including factories, plants, freeways, soil sources, house construction, and biomass burning. Advection also contributed to pollution levels in radiation-advection fogs. The scavenging of NH 3 and coarse particles by fog droplets was the main cause for the high mean pH value of 5.9. In-phase temporal evolution of TIC, [SO 42-], [NO 3-], SO 2, NO 2, PM 10 and S/LWC (S: the surface area of fog droplets per unit volume of air; LWC: liquid water content) was found to be due to the interaction of air pollutants and fog droplets, change of air mass due to advection, and so on. S/LWC seemed to be a better indicator for describing the relationship between TIC and microphysics with respect to LWC. A formula between TIC and S/LWC was derived and the related parameters were discussed. Depositions of chemical species in fog cases were estimated and the result showed that deposition was efficient.

  17. The chemical composition of fogs and clouds in Southern California

    SciTech Connect

    Munger, J.W.

    1989-01-01

    The major inorganic species in cloud and fog water samples were NH{sub 4}{sup +}, H{sup +}, NO{sub 3}{sup {minus}}, and SO{sub 4}{sup 2{minus}}. Concentrations in fog water samples were 1 - 10 {times} 10{sup {minus}3} M; pH values ranged from {approx equal} 2 to 6. Nitrate usually exceeded sulfate. Acidity depended on the availability of NH{sub 3} from agricultural operations. Stratus cloudwater had somewhat lower concentrations; pH values were in the range 3-4. The major factors accounting for variation in fog- or cloudwater composition were the preexisting aerosol and gas concentrations and variations in liquid water content. Deposition and entrainment or advection of different air masses were also important during extended cloud or fog episodes. The droplet size dependence of cloudwater composition was investigated on one occasion in an intercepted coastal stratus clouds. Concentrations of S(IV) and CH{sub 2}O in the range 100-1000 {mu}M were observed in fogwater from urban sites in Southern California. Lower concentrations were observed in stratus clouds. The high levels of S(IV) and CH{sub 2}O were attributed to the formation of hydroxymethanesulfonate (HMSA), the S(IV) adduct of CH{sub 2}O. Direct measurements of HMSA in fogwater samples from Bakersfield, CA were made by ion-pairing chromatography. Glyoxal and methyglyoxal were observed at concentrations comparable to CH{sub 2}O in fogwater samples from Riverside, CA and in stratus cloudwater samples from sites along the Santa Barbara Channel.

  18. Experiments on fog prediction based on multi-models

    NASA Astrophysics Data System (ADS)

    Shi, C.; Wang, L.; Zhang, H.; Deng, X.

    2010-07-01

    Fog is a boundary-layer weather phenomenon with abundant water droplets or crystals that reduces visibility to less than 1 km. The low visibility on fog days usually endangers all kinds of transportation and causes huge economic losses. To numerically forecast fog, a series of numerical experiments were conducted utilizing a mesoscale meteorological model (MM5) and a one-dimension (1D) fog model (PAFOG) with detailed microphysics processes. First, the two models were coupled. MM5 provided the initial and hourly top boundary conditions (IC/BC) for PAFOG, and some other necessary input parameters, including the low, middle and high cloud covers, landuse, and geostrophic winds, etc. Thus, we can run PAFOG for any interested area. Then, the PAFOG was run using two kinds of ICs/BCs for 9 fog events observed in Nanjing during the winters of 2006 and 2007. Detailed comparisons of model results from MM5, PAFOG with two kinds of ICs/BCs for two cases with observations are presented in this paper. The results show that the couple of the two models is successful. PAFOG outperformed MM5 in simulating radiation fog; however, MM5 performed better than PAFOG in simulating advection fog. This suggests that the couple method still need to improve. The impacts of advection on fog cannot be revealed by the top boundary conditions.

  19. Fog Machines, Vapors, and Phase Diagrams

    ERIC Educational Resources Information Center

    Vitz, Ed

    2008-01-01

    A series of demonstrations is described that elucidate the operation of commercial fog machines by using common laboratory equipment and supplies. The formation of fogs, or "mixing clouds", is discussed in terms of the phase diagram for water and other chemical principles. The demonstrations can be adapted for presentation suitable for elementary…

  20. Measurement of large spiral and target waves in chemical reaction-diffusion-advection systems: turbulent diffusion enhances pattern formation.

    PubMed

    von Kameke, A; Huhn, F; Muñuzuri, A P; Pérez-Muñuzuri, V

    2013-02-22

    In the absence of advection, reaction-diffusion systems are able to organize into spatiotemporal patterns, in particular spiral and target waves. Whenever advection is present that can be parametrized in terms of effective or turbulent diffusion D(*), these patterns should be attainable on a much greater, boosted length scale. However, so far, experimental evidence of these boosted patterns in a turbulent flow was lacking. Here, we report the first experimental observation of boosted target and spiral patterns in an excitable chemical reaction in a quasi-two-dimensional turbulent flow. The wave patterns observed are ~50 times larger than in the case of molecular diffusion only. We vary the turbulent diffusion coefficient D(*) of the flow and find that the fundamental Fisher-Kolmogorov-Petrovsky-Piskunov equation, v(f) proportional sqrt[D(*)], for the asymptotic speed of a reactive wave remains valid. However, not all measures of the boosted wave scale with D(*) as expected from molecular diffusion, since the wave fronts turn out to be highly filamentous.

  1. Numerical study of sea fogs off the west coast of the Korean Peninsula using a Single Column Model coupled with WRF

    NASA Astrophysics Data System (ADS)

    Kim, C.; Yum, S. S.

    2010-12-01

    Sea fog is a weather phenomenon that usually occurs below a marine boundary layer. Over the past several decades, efforts have been made to understand clearly the physical mechanisms of formation, evolution and dissipation of sea fogs using numerical modeling. Recently, 3D numerical simulations with a very high horizontal and vertical resolution have been carried out using mesoscale models to identify the influences of the turbulent mixing within PBL, radiative cooling at the fog top, even aerosols, on the formation of sea fogs. However, expensive computation cost is a big concern for these 3D model simulations with high resolution. Alternatively approach is to use a 1D model, i.e., single column model. However, a typical 1D model does not resolve the horizontal advection and pressure gradient force and therefore it is limited to radiation fog studies. More recent approach is to couple a 1D model with a 3D model to compensate for the limitation of a 1D model. In this study, WRFV3.1.1 is used as a 3D model and Cloud Layers Unified By Binormals (CLUBB) is employed as a 1D model. For the 3D simulation, three nested domains of 18 km, 6 km, 2 km are used along with 64 layers in the vertical. Horizontal advections of heat and moisture, geostrophic winds and vertical motion produced every hour from WRFV3.1.1 are provided as an external forcing into the 1D model, CLUBB. CLUBB is designed for studying stable boundary layer as well as convective boundary layer and also supports sophisticated double moment microphysics (e.g., Khairoutdinov and Kogan scheme, and Morrison scheme). Several sea fog events observed in the eastern part of the Yellow Sea near the west coast of Korea are simulated and the effects of radiative cooling and turbulence are examined and a sensitivity tests of microphysics are done using CLUBB. Detailed results will be presented in the conference.

  2. Formation and transformation of magnetite (Fe[sub 3]O[sub 4]) on steel surfaces under continuous and cyclic water fog testing

    SciTech Connect

    Nasrazadani, S. ); Raman, A. )

    1993-04-01

    Formation and transformation of magnetite on two selected low-alloy structural steels were studied using cyclic and continuous water fog tests. It is shown that continuous wetting of steel surfaces results in the formation of magnetite as the main constituent of rust formed. However, in wet/dry fog cycles with drying periods of more than 2 min in every 30-min cycle, a defective spinel phase similar to [gamma]-Fe[sub 2]O[sub 3] forms. Continuous wetting and fast rusting appear to be the main criteria for the stability of magnetite. Both the magnetite and the defective spinel phase [gamma]-Fe[sub 2]O[sub 3] transform to [gamma]-FeOOH first and to [alpha]-FeOOH ultimately under repeated drying conditions, mostly controlled by electrochemical oxidation process. Magnetite formed on steel surface in crevices in the open atmosphere is held stable by the lack of electrochemical oxidation conditions or activation energy for spontaneous oxidation in air.

  3. Pesticide occurrence and distribution in fog collected near Monterey, California

    SciTech Connect

    Schomburg, C.J.; Glotfelty, D.E. ); Seiber, J.N. )

    1991-01-01

    The authors analyzed pesticides in air and fog in several fog events sampled near Monterey, CA, to determine whether the uptake of pesticides in advected oceanic fog was different from uptake in fog forming under stagnant inversion conditions in California's Central Valley in the winter. Data for several pesticides common to both ares showed that the pesticide content and distribution were remarkable similar in the two locations. The conversion of organophosphorus insecticides to their corresponding oxons, and aqueous-phase enrichment factors, were also very similar. Evidence is presented to support the hypothesis that enhanced pesticide concentration in fogwater is caused by strongly sorptive nonfilterable particles and colloids in the fog liquid that are derived from atmospheric particles.

  4. Characterization of multilayer anti-fog coatings.

    PubMed

    Chevallier, Pascale; Turgeon, Stéphane; Sarra-Bournet, Christian; Turcotte, Raphaël; Laroche, Gaétan

    2011-03-01

    Fog formation on transparent substrates constitutes a major challenge in several optical applications requiring excellent light transmission characteristics. Anti-fog coatings are hydrophilic, enabling water to spread uniformly on the surface rather than form dispersed droplets. Despite the development of several anti-fog coating strategies, the long-term stability, adherence to the underlying substrate, and resistance to cleaning procedures are not yet optimal. We report on a polymer-based anti-fog coating covalently grafted onto glass surfaces by means of a multistep process. Glass substrates were first activated by plasma functionalization to provide amino groups on the surface, resulting in the subsequent covalent bonding of the polymeric layers. The anti-fog coating was then created by the successive spin coating of (poly(ethylene-maleic anhydride) (PEMA) and poly(vinyl alcohol) (PVA) layers. PEMA acted as an interface by covalently reacting with both the glass surface amino functionalities and the PVA hydroxyl groups, while PVA added the necessary surface hydrophilicity to provide anti-fog properties. Each step of the procedure was monitored by XPS, which confirmed the successful grafting of the coating. Coating thickness was evaluated by profilometry, nanoindentation, and UV visible light transmission. The hydrophilic nature of the anti-fog coating was assessed by water contact angle (CA), and its anti-fog efficiency was determined visually and tested quantitatively for the first time using an ASTM standard protocol. Results show that the PEMA/PVA coating not only delayed the initial period required for fog formation but also decreased the rate of light transmission decay. Finally, following a 24 hour immersion in water, these PEMA/PVA coatings remained stable and preserved their anti-fog properties.

  5. Fog deposition at a windward Costa Rican cloud forest site

    NASA Astrophysics Data System (ADS)

    Frumau, K. F. A.; Bruijnzeel, L. A.; Tobon-Marin, C.

    2010-07-01

    The hydrological importance of tropical montane cloud forests is recognized increasingly, mostly with respect to the additional water inputs provided by the capture of fog by the forest canopy compared to a non-forested situation (e.g. pasture) in the same environmental setting. The deposition of fog (interception) consists of two components, viz. advectional impaction against roughness elements in the landscape, and vertical settlement both by turbulent diffusion and by gravitational settling. Turbulent diffusion being a function of the aerodynamic roughness of the surface it is typically enhanced over forest compared to pasture. In windward montane areas fog often consists of stratus clouds being forced uphill with the cloud being "stripped" by roughness elements in the landscape. However, due to rain-generating processes these clouds rarely have fog-sized droplets only and larger drops are present as well. Under sufficiently strong wind speeds (e.g. in the trade-wind belt), drizzle-sized droplets tend to follow the terrain and behave like fog. Consequently, there is no unbiased manner in which to separate between fog and drizzle using conventional fog and rain gauges only. Similarly, hydrologically effective precipitation (inclined rainfall) is difficult to determine in mountainous areas, which complicates the determination of fog deposition using wet-canopy water budget approaches. The deposition of fog to a windward Costa Rican montane cloud forest was studied during a full hydrological year (between 1 July 2003 and 1 July 2004). Fog deposition was estimated from the wet canopy water budget as the difference between hydrologically effective precipitation and the sum of throughfall, stemflow, and interception loss. The results show that fog interception constituted a much smaller contribution at this site compared to wind-driven drizzle.

  6. Urban-rural fog differences in Belgrade area, Serbia

    NASA Astrophysics Data System (ADS)

    Vujović, Dragana; Todorović, Nedeljko

    2016-12-01

    Urban/rural fog appearance during the last 27 years in the Belgrade region is analysed using hourly meteorological records from two meteorological stations: an urban station at Belgrade-Vračar (BV) and a rural station at Belgrade-Airport (BA). The effects of urban development on fog formation are discussed through analysis of fog frequency trends and comparison with a number of meteorological parameters. The mean annual and the mean annual minimum temperatures were greater at the urban BV station than at the rural BA station. The mean monthly relative humidity and the mean monthly water vapour pressure were greater at the rural than urban station. During the period of research (1988-2014), BA experiences 425 more days with fog than BV, which means that BV experiences fog for 62.68% of foggy days at BA. Trends in the number of days with fog were statistically non-significant. We analysed the fog occurrence during different types of weather. Fog in urban BV occurred more frequently during cyclonal circulation (in 52.75% of cases). In rural BA, the trend was the opposite and fog appeared more frequently during anticyclonic circulation (in 53.58% of cases). Fog at BV occurred most frequently in stable anticyclonic weather with light wind, when a temperature inversion existed (21.86% of cases). Most frequently, fog at BA occurred in the morning and only lasted a short time, followed by clearer skies during the anticyclonic warm and dry weather (22.55% of cases).

  7. Analysis of an extremely dense regional fog event in Eastern China using a mesoscale model

    NASA Astrophysics Data System (ADS)

    Shi, Chune; Yang, Jun; Qiu, Mingyan; Zhang, Hao; Zhang, Su; Li, Zihua

    2010-03-01

    An unusually dense regional advection-radiation fog event over Anhui and the surrounding provinces in eastern China during Dec. 25-27, 2006, was investigated. At its mature stage, the fog covered most Anhui and parts of the surrounding provinces, reducing visibility to 100 m or less. It lasted more than 36 consecutive hours in some places. A mesoscale meteorological model (MM5), together with back-trajectory analysis, was used to investigate this fog event. The observations from a field station as well as hundreds of routine stations, along with two sets of visibility computing methods, were used to quantitatively and objectively validate the MM5 simulated liquid water content (LWC) and visibility. The verifications demonstrate that MM5 has a better fog predictability for the first day compared to the second day forecast, and better fog predictability compared to dense fog predictability with regard to the probability of detection (POD) and the threat score (TS). The new visibility algorithm that uses both LWC and number density of fog droplets significantly outperforms the conventional LWC-only based one in the fog prediction in terms of the POD score, especially for dense fog prediction. The objective verification in this work is the first time conducted for MM5 fog prediction, with which we can better understand the performance of simulated temporal and spatial fog coverage. The back-trajectory and sensitivity experiments confirm that subsidence and the steady warm and moist advections from southeast and southwest maintained the dense fog while the northwesterly dry wind resulted in dissipation of the fog.

  8. Impact of Air Pollution on California Central Valley Fog Frequency

    NASA Astrophysics Data System (ADS)

    Gray, E.; Baldocchi, D. D.; Goldstein, A. H.

    2015-12-01

    Throughout the 20th century, trends in California Central Valley fog frequency have changed dramatically without explanation. While episodes of dense radiation fog, known regionally as Tule Fog, increased steadily from 1930-1970, analysis from both ground and remote sensing measurements confirm a 46-50% reduction in fog days in the last 30 years (Baldocchi and Waller, 2014, Herkes et al., 2014). The dominant hypotheses suggest that the recent decline in radiation fog can be explained by the rising temperatures associated with climate change or urban heat island effect. This assertion fails to explain the significant increase in Central Valley fog midcentury. Here we instead assert that changes in air pollution, rather than climate, better support this upward then downward temporal trend. Automobile use greatly increased emissions of nitrogen oxide (NOx) midcentury, followed by a large decrease in vehicle emissions due to statewide regulation from 1980 to present. In the Central Valley, NOx from automobile emissions contributes to the formation ammonium nitrate (NH4NO3), the dominant hygroscopic aerosol in the valley's wintertime boundary layer that can act as cloud condensation nuclei (CCN) necessary for fog droplet formation. Thus, changes in air pollution not only affect the number of CCN, but may also impact the density and persistence of fog episodes. Using NOAA meteorological records throughout the twentieth century, we will show the correlation between fog frequency, air pollution, and climatic drivers. We conclude that fog trends are closely correlated with changes in air pollution, rather than solely climate change.

  9. Nonrainfall water origins and formation mechanisms.

    PubMed

    Kaseke, Kudzai Farai; Wang, Lixin; Seely, Mary K

    2017-03-01

    Dryland ecosystems cover 40% of the total land surface on Earth and are defined broadly as zones where precipitation is considerably less than the potential evapotranspiration. Nonrainfall waters (for example, fog and dew) are the least-studied and least-characterized components of the hydrological cycle, although they supply critical amounts of water for dryland ecosystems. The sources of nonrainfall waters are largely unknown for most systems. In addition, most field and modeling studies tend to consider all nonrainfall inputs as a single category because of technical constraints, which hinders prediction of dryland responses to future warming conditions. This study uses multiple stable isotopes ((2)H, (18)O, and (17)O) to show that fog and dew have multiple origins and that groundwater in drylands can be recycled via evapotranspiration and redistributed to the upper soil profile as nonrainfall water. Surprisingly, the non-ocean-derived (locally generated) fog accounts for more than half of the total fog events, suggesting a potential shift from advection-dominated fog to radiation-dominated fog in the fog zone of the Namib Desert. This shift will have implications on the flora and fauna distribution in this fog-dependent system. We also demonstrate that fog and dew can be differentiated on the basis of the dominant fractionation (equilibrium and kinetic) processes during their formation using the (17)O-(18)O relationship. Our results are of great significance in an era of global climate change where the importance of nonrainfall water increases because rainfall is predicted to decline in many dryland ecosystems.

  10. Nonrainfall water origins and formation mechanisms

    PubMed Central

    Kaseke, Kudzai Farai; Wang, Lixin; Seely, Mary K.

    2017-01-01

    Dryland ecosystems cover 40% of the total land surface on Earth and are defined broadly as zones where precipitation is considerably less than the potential evapotranspiration. Nonrainfall waters (for example, fog and dew) are the least-studied and least-characterized components of the hydrological cycle, although they supply critical amounts of water for dryland ecosystems. The sources of nonrainfall waters are largely unknown for most systems. In addition, most field and modeling studies tend to consider all nonrainfall inputs as a single category because of technical constraints, which hinders prediction of dryland responses to future warming conditions. This study uses multiple stable isotopes (2H, 18O, and 17O) to show that fog and dew have multiple origins and that groundwater in drylands can be recycled via evapotranspiration and redistributed to the upper soil profile as nonrainfall water. Surprisingly, the non–ocean-derived (locally generated) fog accounts for more than half of the total fog events, suggesting a potential shift from advection-dominated fog to radiation-dominated fog in the fog zone of the Namib Desert. This shift will have implications on the flora and fauna distribution in this fog-dependent system. We also demonstrate that fog and dew can be differentiated on the basis of the dominant fractionation (equilibrium and kinetic) processes during their formation using the 17O-18O relationship. Our results are of great significance in an era of global climate change where the importance of nonrainfall water increases because rainfall is predicted to decline in many dryland ecosystems. PMID:28345058

  11. An Examination of the Evolution of Radiation and Advection Fogs

    DTIC Science & Technology

    1993-01-01

    Series 349. The Chemistry of Acid Rain-Sources andAtmospheric Processes , American Chemical Society, Washington, DC, 250-257. Wattle, B.J,, E.J. Mack...are not to be construe𔃽 as an official Department of the Army position, unless so designated by other authorized documents. The citation of trade...5.1.2 Chemical Nature of CCN. .. .. ..... ................ . 29 5.1.3 Up-Stream Conditioning ........ ................. ... 30 5.2 Initiation Stage

  12. Observational Research on Fog Physicochemical Properties in Nanjing, China

    NASA Astrophysics Data System (ADS)

    Niu, S.; Lu, C.; Zhao, L.; Lv, J.; Yang, J.

    2010-07-01

    A comprehensive fog in situ observation was carried out at Pancheng in Nanjing area of China during December 2006 and December 2007, including the measurement of fog droplet spectra, surface meteorological elements, boundary layer structure and visibility as well as the collection of fog water. Some new microphysical features and the reasons why low visibility (less than 50 m) lasts for around 40 h in an unusual fog event (12/24/2006-12/27/2006) are examined. The 5-min-average maximum value of liquid water content (LWC) is found extraordinarily higher than 0.5 g m-3. But it is reasonable partly because of high fog top, long-wave radiative cooling, and partly because of the significant positive correlations of number concentration (N) vs. average radius (ra) and droplet spectra standard deviation (SD) vs. ra. The possible causes for the positive correlation of N vs. ra are studied. In general, the development of collision and coalescence can consume small droplets, causing decrease of N and increase of ra. However, due to warm and moist air and sufficient cloud condensation nuclei in this site, small droplets are reproduced through nucleation and condensation. As a result, N is proportional to ra. Furthermore, the correlation between liquid water content (LWC) and N is also positive. Prolonged low visibility is directly caused by the synchronous high LWC and N, and essentially by stable boundary layer structure under the influence of warm advection, sufficient water vapor provided by moisture advection and substantial cloud condensation nuclei (CCN) in the observation site. In addition, with the 37 fog water samples in 9 fog events, fog chemistry is analyzed. Total ionic concentration (TIC), electrical conductivity (EC) in fog samples and local emissions of pollutants are one or two orders of magnitude higher than those found in Europe or South America for instance. Scavenging of NH3 and coarse particles by fog droplets are the main causes for high mean pH value, 5

  13. @KarlTheFog Has Been Mapped!

    USGS Publications Warehouse

    Torregrosa, Alicia

    2016-01-01

    Within the world of mapping, clouds are a pesky interference to be removed from satellite remote sensed imagery.  However, to many of us, that is a waste of pixels. Cloud maps are becoming increasingly valuable in the quest to understand land cover change and surface processes. In coastal California, the dynamic summertime interactions between air masses, the ocean, and topography result in blankets of fog and low clouds flowing into low lying areas of the San Francisco Bay Area. The low clouds and fog advected from the Pacific bring moisture and shade to coastal ecosystems. This acts to reduce temperatures and evapotranspiration stress during the otherwise arid Mediterranean climate season, in turn impacting vegetation distribution, irrigation needs, and urban energy consumption.

  14. Fog collection in the western Mediterranean basin (Valencia region, Spain)

    NASA Astrophysics Data System (ADS)

    Estrela, María J.; Valiente, José A.; Corell, David; Millán, Millán M.

    2008-03-01

    Four different mountainous locations were selected in the Valencia region, East coast of the Iberian Peninsula, for fog water collection studies. Data for 2004 were obtained by means of an instrument ensemble consisting essentially of a passive cylindrical fog water collector, a raingauge, a wind direction and velocity sensor and a temperature and humidity probe. An approximate data reduction technique was also found for this specific ensemble to eliminate the simultaneous rain water component from the fog water measurements. Main results indicate that fog water collection holds significant potential in this region, and especially for southern locations. Annual rates of fog water yield can be as high as 7.0 l/m 2/day in the southern locations, in contrast to 2.0 l/m 2/day collected at one site in a northern location. The highest summer fog water yield was 4.6 l/m 2/day, a relatively large value. Except for the summer period, fog episodes delivering sizeable water volumes are inherently coupled to rainfall. Hourly frequencies of fog collection were also examined to show a distinct daily cycle in summer, denoting orographic fog formation during this period. Lastly, winds were analysed to resolve the most suitable directions for fog collector alignment.

  15. Distribution and long-term trends in various fog types over South Korea

    NASA Astrophysics Data System (ADS)

    Belorid, Miloslav; Lee, Chong Bum; Kim, Jea-Chul; Cheon, Tae-Hun

    2015-11-01

    This study analyzed the spatial and temporal distributions of various fog types over South Korea. Six types of fogs were identified using a classification algorithm based on simple conceptual models of fog formation. The algorithm was applied to a 25-year record of meteorological observations. The most common fog types were radiation fog, prevailing at inland stations, and precipitation fog at coastal and island stations. Declining temporal trends in the frequency of fog events ranging between 2.1 and 10.9 fog events per decade were found at eight inland and two coastal stations. Long-term trends for each fog type show that the decrease in the frequency of fog events is mainly due to a decrease in the frequency of radiation fogs ranging between 1.1 and 8.5 fog events per decade. To identify the potential factors related to the decrease in radiation fog events, the temporal trends in annual mean nocturnal maximal cooling rates and annual mean nocturnal specific humidity during nights with clear sky and clam winds were examined. The results show that the decrease in the frequency of radiation fog events is associated mainly with the pattern of urbanization occurring during the past two decades.

  16. On the Influence of a Simple Microphysics Parametrization on Radiation Fog Modelling: A Case Study During ParisFog

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaojing; Musson-Genon, Luc; Dupont, Eric; Milliez, Maya; Carissimo, Bertrand

    2014-05-01

    A detailed numerical simulation of a radiation fog event with a single column model is presented, which takes into account recent developments in microphysical parametrizations. One-dimensional simulations are performed using the computational fluid dynamics model Code_Saturne and the results are compared to a very detailed in situ dataset collected during the ParisFog campaign, which took place near Paris, France, during the winter 2006-2007. Special attention is given to the detailed and complete diurnal simulations and to the role of microphysics in the fog life cycle. The comparison between the simulated and the observed visibility, in the single-column model case study, shows that the evolution of radiation fog is correctly simulated. Sensitivity simulations show that fog development and dissipation are sensitive to the droplet-size distribution through sedimentation/deposition processes but the aerosol number concentration in the coarse mode has a low impact on the time of fog formation.

  17. Drop size distributions and related properties of fog for five locations measured from aircraft

    NASA Technical Reports Server (NTRS)

    Zak, J. Allen

    1994-01-01

    Fog drop size distributions were collected from aircraft as part of the Synthetic Vision Technology Demonstration Program. Three west coast marine advection fogs, one frontal fog, and a radiation fog were sampled from the top of the cloud to the bottom as the aircraft descended on a 3-degree glideslope. Drop size versus altitude versus concentration are shown in three dimensional plots for each 10-meter altitude interval from 1-minute samples. Also shown are median volume radius and liquid water content. Advection fogs contained the largest drops with median volume radius of 5-8 micrometers, although the drop sizes in the radiation fog were also large just above the runway surface. Liquid water content increased with height, and the total number of drops generally increased with time. Multimodal variations in number density and particle size were noted in most samples where there was a peak concentration of small drops (2-5 micrometers) at low altitudes, midaltitude peak of drops 5-11 micrometers, and high-altitude peak of the larger drops (11-15 micrometers and above). These observations are compared with others and corroborate previous results in fog gross properties, although there is considerable variation with time and altitude even in the same type of fog.

  18. Fog Simulations Based on Multi-Model System: A Feasibility Study

    NASA Astrophysics Data System (ADS)

    Shi, Chune; Wang, Lei; Zhang, Hao; Zhang, Su; Deng, Xueliang; Li, Yaosun; Qiu, Mingyan

    2012-05-01

    Accurate forecasts of fog and visibility are very important to air and high way traffic, and are still a big challenge. A 1D fog model (PAFOG) is coupled to MM5 by obtaining the initial and boundary conditions (IC/BC) and some other necessary input parameters from MM5. Thus, PAFOG can be run for any area of interest. On the other hand, MM5 itself can be used to simulate fog events over a large domain. This paper presents evaluations of the fog predictability of these two systems for December of 2006 and December of 2007, with nine regional fog events observed in a field experiment, as well as over a large domain in eastern China. Among the simulations of the nine fog events by the two systems, two cases were investigated in detail. Daily results of ground level meteorology were validated against the routine observations at the CMA observational network. Daily fog occurrences for the two study periods was validated in Nanjing. General performance of the two models for the nine fog cases are presented by comparing with routine and field observational data. The results of MM5 and PAFOG for two typical fog cases are verified in detail against field observations. The verifications demonstrated that all methods tended to overestimate fog occurrence, especially for near-fog cases. In terms of TS/ETS, the LWC-only threshold with MM5 showed the best performance, while PAFOG showed the worst. MM5 performed better for advection-radiation fog than for radiation fog, and PAFOG could be an alternative tool for forecasting radiation fogs. PAFOG did show advantages over MM5 on the fog dissipation time. The performance of PAFOG highly depended on the quality of MM5 output. The sensitive runs of PAFOG with different IC/BC showed the capability of using MM5 output to run the 1D model and the high sensitivity of PAFOG on cloud cover. Future works should intensify the study of how to improve the quality of input data (e.g. cloud cover, advection, large scale subsidence) for the 1D

  19. Research on measurement method of optical transmittance of the artificial fog

    NASA Astrophysics Data System (ADS)

    Hu, Jianghua; Jian, Chaochao; Cui, Guangzhen; Lv, Xuliang; Rong, Xianhui

    2016-10-01

    The attenuation of light was a common result that the light was absorbed and scattered by the artificial fog particles when it transmitted in the artificial fog. The absorbing attenuation process of light transmission in the artificial fog was that the artificial fog converting incident light energy into other forms of internal energy (such as heat energy). The scattering attenuation process of light transmission in the artificial fog was that the artificial fog particles intercepting incident radiation energy to form infrasonic waves and to radiate peripherally so that the incident light energy was reduced on the original direction of transmission. The mechanism of light transmission attenuation in the artificial fog was analyzed. The formation method of the artificial fog was expounded and the measuring principle of the artificial fog transmittance was described. A simple and reliable measurement method of the optical transmittance of the artificial fog in the fog chamber was proposed. The optical transmittance measurement system of the artificial fog was built by using incandescent lamp, power with steady current and voltage, lens, selenium photocell, micro-galvanometer, optical bench, hygrothermograph, humidifier, etc. Under different conditions of humidity, the optical transmittance of the artificial fog was obtained on the basis of measuring the photocurrent before the fog was formed in the fog chamber. The test results show that the measurement system is stable and reliable. During the 43 minutes after the artificial fog was formed, the optical transmittance of the artificial fog was averagely less than 5 percent and the optical transmittance increased gradually with the extension of time. In addition, the optical transmittance of artificial fog didn't produce obvious change while air humidity increased from 68.7% to 85%. The measurement system can be used to measure transmittance of smoke screen, water mist and other aerosol.

  20. Pathways for Advective Transport

    DTIC Science & Technology

    2001-01-19

    the approach is given and an application to the Gulf of Mexico is described where the analysis precisely identifies the boundaries of coherent vortical structures as well as pathways for advective transport.

  1. AC fog withstand test on contaminated insulators by steam fog

    SciTech Connect

    Arai, J.N.

    1982-11-01

    This paper describes the results of an investigation into how steam fog parameters affect the withstand voltage of artificially contaminated insulators by the fog withstand method. Established the correlation between the steam flow rate and liquid water content of the fog. The fog withstand voltage showed a lower value with little dispersion at about 3 to 10 g/m/sup 3/ of the maximum liquid water content. The minimum fog withstand voltage agreed well with the minimum flashover voltage obtained under natural conditions. The authors suggest that, for the fog withstand test using steam fog, the ideal fog condition would be about 3 to 7 g/m/sup 3/ of the maximum liquid water content of the fog.

  2. Warm fog dispersal

    NASA Technical Reports Server (NTRS)

    Frost, W.

    1983-01-01

    The charged particle generator was further tested after some design modification. The generator performance was measured with additional instrumentation and found to confirm previous measurements. Plans for a field testing were than developed. The overall status of the program and the field test plans were presented to a group of atmospheric scientists and electrostatic experts at the NASA/MSFC sponsored USRA Workshop on Electrostatic Fog Dispersal at NCAR, Boulder, Colorado discussed in previous sections. The recommendations from this workshop are being evaluated as to whether NASA should proceed with the field test or whether further theoretical research on the phenomenon of electrostatic fog dispersal and additional development of the charged particle generator should be carried out. Information obtained from the USRA Workshop clearly identified three physical mechanisms that could possibly influence the fog dispersal process, which heretofore have not been considered, and which may provide additional insight to the direction of further fog dispersal work. These mechanisms are: the effect of corona discharge on the electric field strength at the surface, the influx of fog into the cleared volume by turbulent diffusion, and the increase in supersaturation as liquid water is removed, activating haze particles, and thus generating more fog. Plans are being formulated to investigate these mechanisms.

  3. Size-dependent particle activation properties in fog during the ParisFog 2012/13 field campaign

    NASA Astrophysics Data System (ADS)

    Hammer, E.; Gysel, M.; Roberts, G. C.; Elias, T.; Hofer, J.; Hoyle, C. R.; Bukowiecki, N.; Dupont, J.-C.; Burnet, F.; Baltensperger, U.; Weingartner, E.

    2014-04-01

    during the fog formation, was determined. The median SSpeak value was estimated to be in the range from 0.031 to 0.046% (upper and lower limit estimations), which is in good agreement with previous experimental and modeling studies of fog.

  4. Fog deposition to the Atacama desert

    NASA Astrophysics Data System (ADS)

    Westbeld, A.; Klemm, O.; Griessbaum, F.; Sträter, E.; Larrain, H.; Osses, P.; Cereceda, P.

    2010-07-01

    In the Atacama Desert, one of the driest places on earth, fog deposition plays an important role for the water balance and for the survival of vulnerable ecosystems. The eddy covariance method, previously applied for the quantification of fog deposition to forests in various parts of the world, was used for the first time to measure deposition of fog water to a desert. We estimated the amount of water available for the ecosystem by deposition and determined the relevant processes driving fog deposition. This is especially important for the species Tillandsia landbecki living in coastal Atacama at the limit of plant existence with fog and dew being the only sources of liquid water. Between 31 July and 19 August, 2008, measurements were realized in a 31 ha large Tillandsia carpet at Cerro Guanaco, located 15 km south of Iquique, northern Chile. Several data quality assurance procedures were applied. For the values in compliance with the applied criteria, the mean total deposition per hour was determined (0.04 L per m2) for foggy periods. This number was applied to estimate the amount of water deposited during the measuring period, during the entire month of August 2008, and throughout a whole year. For August 2008, a frequency of fog of 16 %, as established during the measuring period, was assumed. The frequency for a whole year was estimated from the differences of the collected amount of water obtained with standard fog collectors installed at Cerro Guanaco in an earlier study. Calculations resulted in an amount of 2.5 L per m2 of deposited fog water for the measuring period. During the entire August, 4.4 L per m2 have likely been available, and for a whole year, a total of 25 L per m2 was estimated to have reached the surface. Inaccuracies could have been caused by the low amount of data applied, and by a possible underestimation of the deposition due to additional formation of radiation fog during the fog events. Three days were used for further analysis because

  5. Size-dependent particle activation properties in fog during the ParisFog 2012/13 field campaign

    NASA Astrophysics Data System (ADS)

    Hammer, E.; Gysel, M.; Roberts, G. C.; Elias, T.; Hofer, J.; Hoyle, C. R.; Bukowiecki, N.; Dupont, J.-C.; Burnet, F.; Baltensperger, U.; Weingartner, E.

    2014-10-01

    Fog-induced visibility reduction is responsible for a variety of hazards in the transport sector. Therefore there is a large demand for an improved understanding of fog formation and thus improved forecasts. Improved fog forecasts require a better understanding of the numerous complex mechanisms during the fog life cycle. During winter 2012/13 a field campaign called ParisFog aiming at fog research took place at SIRTA (Instrumented Site for Atmospheric Remote Sensing Research). SIRTA is located about 20 km southwest of the Paris city center, France, in a semi-urban environment. In situ activation properties of the prevailing fog were investigated by measuring (1) total and interstitial (non-activated) dry particle number size distributions behind two different inlet systems; (2) interstitial hydrated aerosol and fog droplet size distributions at ambient conditions; and (3) cloud condensation nuclei (CCN) number concentration at different supersaturations (SS) with a CCN counter. The aerosol particles were characterized regarding their hygroscopic properties, fog droplet activation behavior and contribution to light scattering for 17 developed fog events. Low particle hygroscopicity with an overall median of the hygroscopicity parameter, κ, of 0.14 was found, likely caused by substantial influence from local traffic and wood burning emissions. Measurements of the aerosol size distribution at ambient RH revealed that the critical wet diameter, above which the hydrated aerosols activate to fog droplets, is rather large (with a median value of 2.6μm) and is highly variable (ranging from 1 to 5μm) between the different fog events. Thus, the number of activated fog droplets was very small and the non-activated hydrated particles were found to contribute significantly to the observed light scattering and thus to the reduction in visibility. Combining all experimental data, the effective peak supersaturation, SSpeak, a measure of the peak supersaturation during the fog

  6. Impact of activation process on fog life cycle

    NASA Astrophysics Data System (ADS)

    Mazoyer, Marie; Burnet, Frédéric; Lac, Christine; Roberts, Greg; Dupont, Jean-Charles; Haeffelin, Martial; Elias, Thierry

    2015-04-01

    Fogs are complex meteorological system dealing with fine scale processes. Subtle interaction between radiative, dynamic, turbulent and microphysic processes can lead to different fog life cycle, which make prediction difficult. The droplets that composed fogs are formed trough the activation of aerosol particles called CCN (cloud condensation nuclei) described by the Köhler theory (Köhler, 1936). The number and distribution of the droplets activated during fog formation is determined by the aerosols particles properties and number and the ambient vapor supersaturation of the atmosphere. In the frame of the PreViBOSS project, an in-situ measurement platform of fog properties at ground level was deployed at SIRTA (Instrumented Site for Atmospheric Remote Sensing Research) during winter 2010 to 2013. Microphysics data supply a detailed characterization of number size spectrum from dry to wet aerosols particles and inform on the abilities of the aerosols particles to act as a CCN. 48 fog events have been studied. Supersaturation critical values and concentrations of CCN have been determined and linked to aerosols properties. The main impact of aerosols size distribution on activation have been pointed out. The study of droplets spectra evolution reveals the major physical processes into fogs and suggests that even if thermodynamic dominates the fog life cycle, activation process seems to have a significant effect. Large eddy simulation of fog run with Meso-NH model allow to explore precisely the interaction between fog physical processes and to quantify activation impact. Supersaturation modelling is a key point, a new pseudo-prognostic scheme (Thouron et al., 2012) is used. Confrontation between a detailed experimental study and three-dimensional fine scale simulation in LES provides an accurate investigation of the impact of activation process on fog life cycle.

  7. The Fog Remote Sensing and Modeling (FRAM) field project: visibility analysis and remote sensing of fog

    NASA Astrophysics Data System (ADS)

    Gultepe, I.; Minnis, P.; Milbrandt, J.; Cober, S. G.; Nguyen, L.; Flynn, C.; Hansen, B.

    2008-08-01

    The main objective of this work is to describe a research project on fog and visibility, and to summarize the results. The Fog Remote Sensing and Modeling (FRAM) project was designed to focus on 1) development of microphysical parameterizations for model applications, 2) development of remote sensing methods for fog nowcasting/forecasting, 3) understanding of issues related to instrument capabilities and improvement of the analysis, and 4) integration of model data with observations. The FRAM was conducted over three regions of Canada and US. These locations were: 1) Center for Atmospheric Research Experiments (CARE), Egbert, Ontario 2005-2006, 2) Lunenburg, Nova Scotia June of 2006 and 2007, and 3) U.S. Department Of Energy (DOE) ARM Climate Research Facility at Barrow, Alaska, US during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) field program April of 2008; FRAM C, FRAM-L, and ISDAC-FRAM-B, respectively. FRAM-C was undertaken in a continental fog environment while FRAM-L was in a marine environment. The FRAM-B was undertaken to study ice fog conditions. During the project, numerous in-situ measurements were obtained, including droplet and aerosol spectra, precipitation, and visibility. Analysis of satellite microphysical retrievals and visibility parameterizations suggested that improved scientific understanding of fog formation can lead to better forecasting/nowcasting skills benefiting both aviation and public forecasting applications.

  8. Fog Collection and Sustainable Architecture in Atacama Coast

    NASA Astrophysics Data System (ADS)

    Suau, C.

    2010-07-01

    materials and local techniques. This research integrates climatic, structural and constructional factors by employing agile space-frame configurations; implementing appropriate low-passive energy technologies and testing hydrophobic and durable fabrics. The overall design target will upgrade the following aspects: 1. Increasing rate and yield of advection fog that can be anticipated from the fog harvesting rate and the uncertainty of climatic conditions 2. Structural reinforcement of fog collectors through lightweight, modular and deployable space-frames 3. Reducing installation and maintenance of fog collection 4. Purification of drinking water due to concentrations of pollutants 5. Lowering frame impacts on ground and surrounding mainly in lomas The methods mainly consists of literature review; fieldwork; comparative analysis of existing fog collection’s techniques and climatic design simulations.

  9. La Jolla Fog Study

    NASA Astrophysics Data System (ADS)

    Roberts, G. C.; Ramana, M.; Pham, A.; Ramanathan, V.

    2002-12-01

    The Center for Atmospheric Sciences at the Scripps Institution of Oceanography conducted a ground-based experiment to study fog/marine-stratus clouds over the San Diego region during the summer months of 2002. The purpose of the experiment is to understand aerosol/cloud interactions and how they might influence cloud radiative properties and precipitation. We operated several instruments on Mt. Soledad to study aerosol and cloud properties. These instruments include a forward scattering spectrometer probe (FSSP-100) and an aerosol particle sizer (APS) to measure the cloud droplet spectra during fog events, condensation particle counters to determine total aerosol concentrations, cloud condensation nuclei counters to understand aerosol/cloud droplet interactions, a scanning mobility particle sizer (SMPS) to determine dry aerosol number size distributions, and a weather station to relate fog events to local meteorology. Aerosol concentrations showed a diel variation with high and variable particle concentrations during the day, which often were greater than 104 cm-3. Nighttime concentrations were lower (i.e., several thousand cm-3) and exhibited less variation than daytime values. In general, aerosol concentrations do not appear to be correlated to droplet concentrations indicating that local anthropogenic sources may not have a large influence on the coastal fog. Two types of events (haze and fog) have been characterized during this study based on the droplet distribution. A haze event was dominated by droplets less than 5 μm diameter and sometimes exceeded droplet concentrations of 1000 cm-3. There were virtually no particles larger than 5 micron diameter during these events. A fog event was characterized by larger droplets with droplets greater than 5 μm diameter accounting for a bulk of the number concentration. The average effective radius during these fog events was about 5 μm and the droplet concentration rarely exceeded 100 cm-3. On several occasions, a

  10. Fog interception by Ball moss (Tillandsia recurvata)

    NASA Astrophysics Data System (ADS)

    Guevara-Escobar, A.; Cervantes-Jiménez, M.; Suzán-Azpiri, H.; González-Sosa, E.; Hernández-Sandoval, L.; Malda-Barrera, G.; Martínez-Díaz, M.

    2010-03-01

    Interception losses are a major influence in the water yield of vegetated areas. For most storms, interception results in less water reaching the ground. However, fog drip or occult precipitation can result in negative interception because small drops are deposited on all plant surfaces and subsequently fall to the ground once vegetation storage capacities are exceeded. Fog drip is normally disregarded, but for some plant communities, it could be a mechanism offsetting evaporation losses. Tillandsia recurvata is a cosmopolitan epiphyte adapted to arid habitats where fog may be an important water source. Therefore, the interception storage capacity by T. recurvata was measured in controlled conditions through applying simulated rain or fog. The storage capacity was proportional to dry weight mass. Nocturnal stomatic opening in T. recurvata is not only relevant for CO2 but for water vapor, as suggested by the higher weight change of specimens wetted with fog for 1 h at dark in comparison to those wetted during daylight (543±77 vs. 325±56 mg, p=0.048). The coefficients obtained in the laboratory were used together with biomass measurements for T. recurvata in a xeric scrub to calculate the depth of water intercepted. Interception storage capacity (Cmin) was 0.19 and 0.54 mm for rainfall and fog respectively. T. recurvata contributed 20% to the rain interception of their shrub hosts: Acacia farnesiana and Prosopis laevigata. Meteorological data registered during one year at Cadereyta, México showed that radiative fog formation was possible during the dry season. The results showed the potential role of T. recurvata in capturing fog, which probably is a main source of water during the dry season that supports their reproductive and physiological activity at that time. The storage capacity of T. recurvata leaf surfaces could increase the amount of water available for evaporation, but as this species colonise montane forests, the effect could be negative on water

  11. HEMP advection model

    SciTech Connect

    Sharp, R.W. Jr.; Barton, R.T.

    1981-01-21

    A continuous rezoning procedure has been implemented in the computational cycle of a version of the HEMP two-dimensional, Lagrange, fluid dynamics code. The rezoning problem is divided into two steps. The first step requires the solving of ordinary Lagrange equations of motion; the second step consists of adding equipotential grid relaxation along with an advective remapping scheme.

  12. Fog Research: A Review of Past Achievements and Future Perspectives

    NASA Astrophysics Data System (ADS)

    Gultepe, I.; Tardif, R.; Michaelides, S. C.; Cermak, J.; Bott, A.; Bendix, J.; Müller, M. D.; Pagowski, M.; Hansen, B.; Ellrod, G.; Jacobs, W.; Toth, G.; Cober, S. G.

    2007-06-01

    The scientific community that includes meteorologists, physical scientists, engineers, medical doctors, biologists, and environmentalists has shown interest in a better understanding of fog for years because of its effects on, directly or indirectly, the daily life of human beings. The total economic losses associated with the impact of the presence of fog on aviation, marine and land transportation can be comparable to those of tornadoes or, in some cases, winter storms and hurricanes. The number of articles including the word ``fog'' in Journals of American Meteorological Society alone was found to be about 4700, indicating that there is substantial interest in this subject. In spite of this extensive body of work, our ability to accurately forecast/nowcast fog remains limited due to our incomplete understanding of the fog processes over various time and space scales. Fog processes involve droplet microphysics, aerosol chemistry, radiation, turbulence, large/small-scale dynamics, and surface conditions (e.g., partaining to the presence of ice, snow, liquid, plants, and various types of soil). This review paper summarizes past achievements related to the understanding of fog formation, development and decay, and in this respect, the analysis of observations and the development of forecasting models and remote sensing methods are discussed in detail. Finally, future perspectives for fog-related research are highlighted.

  13. Analysis of Dynamical and Thermal Processes Driving Fog and Quasi-Fog Life Cycles Using the 2010-2013 ParisFog Dataset

    NASA Astrophysics Data System (ADS)

    Dupont, J. C.; Haeffelin, M.; Stolaki, S.; Elias, T.

    2016-04-01

    The data from suite of in situ sensors, passive and active remote sensing instruments dedicated to document simultaneously radiative and thermo-dynamical processes driving the fog life cycle at the SIRTA Observatory (instrumented site for atmospheric remote sensing research) near Paris during two periods of 6 months are analysed. The study focuses on the analysis of the relative role of key physical processes and their interactions during fog formation, development and dissipation phases. This work presents, from analysis of detailed observations, the range of values that critical parameters have to take for fog and quasi-fog formation. In our study, we consider fog (horizontal visibility lower than 1 km, a dataset of 300 h) and quasi-fog (horizontal visibility ranging from 1 to 2 km, a dataset of 400 h) events induced by radiative cooling (53 events) and stratus lowering (64 events). For the radiative fog events, (with radiative cooling during prefog conditions), we note that the longwave net radiative flux (around -60 ± 5 W/m2) induces a cooling of the surface layer. The vertical structure of this cooling is controlled by dynamics, that is, wind shear and horizontal and vertical velocities. In case of very low mixing (wind speed below 0.6 m/s), the thermal stability is very strong with a temperature inversion around 3.5 °C for 10 m and a humidity gradient reaching 10 % preventing vertical development of the fog layer. For stratus-lowering fog events, the altitude of the stratus layer, the vertical mixing and the absolute value of humidity are driving parameters of the fog formation. Our statistical analysis shows that a stratus cloud with a cloud base around 170 m and with a small cloud-base subsidence rate of 50 m/h leads to fog, whereas a stratus cloud with a base around 800 m agl, with a larger cloud-base subsidence rate of 190 m/h conducts to quasi-fog situations with an important increase of the stratus liquid water path.

  14. Analysis of Cumulonimbus (Cb), Thunderstorm and Fog for Izmir Adnan Menderes Airport

    NASA Astrophysics Data System (ADS)

    Avsar, Ercument

    2016-07-01

    Demand for airline transport has been increasing day by day with the development of the aviation industry in Turkey. Meteorological conditions are among the most important factors that influence aviation facilities. Meteorological events cause delays and cancellation of flights which create economic and time losses, and they even lead to accidents and breakups. The most important meteorological events that affect the takeoff and landing of airplanes can be listed as wind, runway visual range, cloud, rain, icing, turbulence, and low level windshear. Meteorological events that affect the aviation facilities most often in Adnan Menderes Airport (LTBJ), the fourth largest airport in Turkey in terms of air traffic, are fog, Cumulonimbus (Cb) clouds and thunderstorms (TS-Thunderstorm). Therefore, it is important to identify the occurrence time of these events based on the analysis of data over many years and do the flight plans based on this meteorological information in order to make the aviation facilities safer and without delays. In this study, statistical analysis on the formation of Cb clouds, thunderstorm and foggy days is conducted using observations produced for aviation (METAR) and special observers (SPECI). It is found that there are two types of fog that are observed most often at LTBJ, namely radiation and advection fogs, accordingly to the results of statistical analysis based on data from 2004 to 2014. Fog events are found to occur most often in the months of December and January, during 04:00 - 07:00 UTC time interval, between pressure values over 1015-1020 hPa, in 130-190 degree light breeze (1-5KT) and in temperature levels between 5°C and 8°C. Thunderstorm events recorded at LTBJ between the years 2004 and 2014 are most often observed in the months of January and February, in 120-210 degree gentle breeze winds (6-10KT), and in temperature levels between 8 and 18 °C. Key Words: Adnan Menderes International Airport, LTBJ, Fog, Thunderstorm (TS), Cb

  15. Winter Frost and Fog

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This somewhat oblique blue wide angle Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the 174 km (108 mi) diameter crater, Terby, and its vicinity in December 2004. Located north of Hellas, this region can be covered with seasonal frost and ground-hugging fog, even in the afternoon, despite being north of 30oS. The subtle, wavy pattern is a manifestation of fog.

    Location near: 28oS, 286oW Illumination from: upper left Season: Southern Winter

  16. Pollution Levels in Fog at the Chilean Coast

    NASA Astrophysics Data System (ADS)

    Sträter, E.; Klemm, O.; Westbeld, A.

    2010-07-01

    During July and August 2008 fog water was collected for chemical analysis in Patache, at the coast of northern Chile, 60 km south of Iquique (20°49’S, 70°09’W). Advective fog events occur regularly at the cliff in the coastal range at about 800 m above MSL. People collect these types of fog water at some places along the coast with Large Fog Collectors (LFC) for domestic use and for watering field crops. So far, no chemical analysis of fog water was performed in Patache. Pure fogwater samples (38 samples from 8 fog events) were taken by using a passive Scientific Cylindrical Fog Collector. Major ions and trace metals were quantified. The analyses indicate very high ionic concentrations (mean 3500 µeq/l) and very low pH values (mean 3.3). The mean H+-concentration represents 16 % of the total ionic equivalent concentration. Sulfate is the anion exhibiting the highest concentrations. A mean value of 880 µeq/l was found, which accounts for 24 % of the total mean concentration. In contrast to sulfate, nitrate shows only a low percentage of 8.1 %. Further major ions are sodium (20%) and chloride (19 %), which are typical seasalt ions in coastal fog. High correlations between the measured ions suggest a causal link between concentration in the fog samples and the liquid water content (LWC) of the cloud. The higher the liquid water content the lower are the ionic concentrations. Enrichment factors with sodium as reference ion were calculated to identify potential emission sources contributing to the observed pollutant levels. We found that K+, Na+, Mg2+ and Cl- mainly result from seaspray. Sulfate, however, is enriched by a factor of 13. The measured trace elements are highly enriched by factors up to hundreds of thousands (Zn: 50, Ni: 1800, As: 2400, Cd: 3900, Fe: 100000, Cu: 96000, Pb: 250000). A cluster analysis supports the conclusion that sulfate and the trace elements originate from anthropogenic activities. The sulfate cannot primarily originate from

  17. A One-dimensional Ensemble Forecast and Assimilation System for Fog Prediction

    NASA Astrophysics Data System (ADS)

    Müller, M. D.; Schmutz, C.; Parlow, E.

    2007-06-01

    A probabilistic fog forecast system was designed based on two high resolution numerical 1-D models called COBEL and PAFOG. The 1-D models are coupled to several 3-D numerical weather prediction models and thus are able to consider the effects of advection. To deal with the large uncertainty inherent to fog forecasts, a whole ensemble of 1-D runs is computed using the two different numerical models and a set of different initial conditions in combination with distinct boundary conditions. Initial conditions are obtained from variational data assimilation, which optimally combines observations with a first guess taken from operational 3-D models. The design of the ensemble scheme computes members that should fairly well represent the uncertainty of the current meteorological regime. Verification for an entire fog season reveals the importance of advection in complex terrain. The skill of 1-D fog forecasts is significantly improved if advection is considered. Thus the probabilistic forecast system has the potential to support the forecaster and therefore to provide more accurate fog forecasts.

  18. Revisiting the fog bottle experiment

    NASA Astrophysics Data System (ADS)

    Kamcharean, C.; Khanchong, C.; Wattanakasiwich, P.

    2016-11-01

    In this article we propose an irreversible adiabatic expansion model, modified from previous work, to explain the fog bottle experiment. Our model divides the phenomenon into five thermodynamic states, and we include in our calculation irreversible work pushing a stopper out of the bottle and heat gain from the condensation of saturated vapour. In the experiment, thermodynamic variables including pressure and temperature as functions of time were measured. The work done in pushing the stopper out was measured and the condensation heat was determined using the Clausius-Clapeyron equation to determine saturated vapour pressure. As a result, fog formation was explained through a phase diagram of water showing the saturated vapour pressure during irreversible adiabatic expansion. Also, state variables (P, V and T) and the entropy change of the real process were compared with the reversible and irreversible adiabatic expansion and our modified process. Using a P-T diagram, we show that the amount of reversible work is always higher than the amount of irreversible work, due to dissipative work. According to our modified model, the dissipative work and the heat transferred from condensation cause irreversibility or {{Δ }}{S}{{t}{{o}}{{t}}{{a}}{{l}}}\\gt 0.

  19. On the Measurement of Dewfall and Fog-Droplet Deposition

    NASA Astrophysics Data System (ADS)

    Price, J. D.; Clark, R.

    2014-09-01

    An observational study has been conducted concerning atmospheric dewfall and fog-droplet deposition with application to the formation and maintenance of fog layers. The relationship between dew and fog is discussed together with the challenges and requirements to measure representative values of their deposition to the surface. A practical instrument developed at the UK Met Office Research Unit, Cardington, is described. The instrument is a small portable device that uses a load cell to measure the weight of a pan upon which various types of natural and artificial canopies can be placed, and can measure dewfall and fog-droplet deposition to an accuracy of 0.0005 mm. Dewfall results from this device are shown for a selection of nights under varying conditions. On a given night the overriding factor determining the amount of dew deposition appears to be location. Several dewmeter devices were placed at different locations around the 18 ha Cardington field site for various clear nights and it was found that dew amounts varied significantly, depending on location: canopies with a more open aspect experienced more deposition by up to a factor of two. The results also suggest that the hygroscopic effect of a canopy, whereby water is absorbed into the canopy and topsoil layer before dew formation begins, is also important for the removal of atmospheric water vapour. Results indicate this effect can be of a similar magnitude to dew deposition. Measurements of fog-droplet deposition showed total water deposition rates did not change when thin radiation fog formed. When optically thick adiabatic fog formed, deposition rates were seen to decrease with time or be generally lower than for thinner radiation fog. Further observations are required to establish if the behaviours found are typical for all fogs.

  20. SUMOylation regulates the transcriptional repression activity of FOG-2 and its association with GATA-4.

    PubMed

    Perdomo, José; Jiang, Xing-Mai; Carter, Daniel R; Khachigian, Levon M; Chong, Beng H

    2012-01-01

    Friend of GATA 2 (FOG-2), a co-factor of several GATA transcription factors (GATA-4, -5 and 6), is a critical regulator of coronary vessel formation and heart morphogenesis. Here we demonstrate that FOG-2 is SUMOylated and that this modification modulates its transcriptional activity. FOG-2 SUMOylation occurs at four lysine residues (K324, 471, 915, 955) [corrected]. Three of these residues are part of the characteristic SUMO consensus site (ψKXE), while K955 is found in the less frequent TKXE motif. Absence of SUMOylation did not affect FOG-2's nuclear localization. However, mutation of the FOG-2 SUMOylation sites, or de-SUMOylation, with SENP-1 or SENP-8 resulted in stronger transcriptional repression activity in both heterologous cells and cardiomyocytes. Conversely, increased FOG-2 SUMOylation by overexpression of SUMO-1 or expression of a SUMO-1-FOG-2 fusion protein rendered FOG-2 incapable of repressing GATA-4-mediated activation of the B-type natriuretic peptide (BNP) promoter. Moreover, we demonstrate both increased interaction between a FOG-2 SUMO mutant and GATA-4 and enhanced SUMOylation of wild-type FOG-2 by co-expression of GATA-4. These data suggest a new dynamics in which GATA-4 may alter the activity of FOG-2 by influencing its SUMOylation status.

  1. Size resolved fog water chemistry and its atmospheric implications

    NASA Astrophysics Data System (ADS)

    Chakraborty, Abhishek; Gupta, Tarun; Tripathi, Sachchida; Ervens, Barbara; Bhattu, Deepika

    2015-04-01

    PMF (Positive matrix factorization) revealed presence of some very highly oxidized OA inside fog water samples. From PMF results a method for aqSOA estimation is developed and aqSOA was found to be substantially contributing to total SOA. These findings indicate that light fog with large number of fine droplets can process the ambient aerosols more efficiently than very dense fog with larger droplets where scavenging becomes more important. These findings also highlight the need of incorporating fog size resolved chemistry along with metal chemistry into global models for accurately predicting aqSOA formation and contribution to total organic aerosol loading.

  2. California's fog is far more polluted than acid rain

    SciTech Connect

    Roberts, L.

    1982-11-01

    In the Los Angeles area, measurements reveal that the fog has a pH between 2.5 and 3. Near congested areas, the fog is consistenly acidic and is laden with sulfate, nitrate, ammonium ion, lead, copper, nickel, vanadium and aldehydes. Acid fog formation involves a conversion of SO/sub 2/ and NO/sub x/ to sulfuric and nitric acids. Unlike acid rain, acid fog remains suspended in the air for hours and is a threat to human health as well as vegetation and materials. Fog forms close to the ground where concentrations of pollutants are higher than they are further aloft. Acid fog seems to be related to ground-based pollution sources, particularly power plant and automobile emissions. Samples were collected in locations far from major pollution sources and used to test the composition and acidity of normal fog. The pH values ranged from 3, near Los Angeles, to 7, near Morro Bay. Mathematical models are used to explain changes in acidity over time and to indicate a cyclical pattern.

  3. New method for evaluating high-quality fog protective coatings

    NASA Astrophysics Data System (ADS)

    Czeremuszkin, Grzegorz; Latreche, Mohamed; Mendoza-Suarez, Guillermo

    2011-05-01

    Fogging is commonly observed when humid-warm air contacts the cold surface of a transparent substrate, i.e. eyewear lenses, making the observed image blurred and hazy. To protect from fogging, the lens inner surfaces are protected with Anti-Fog coatings, which render them hydrophilic and induce water vapor condensation as a smooth, thin and invisible film, which uniformly flows down on the lens as the condensation progresses. Coatings differ in protection level, aging kinetics, and susceptibility to contamination. Some perform acceptably in limited conditions, beyond which the condensing water film becomes unstable, nonuniform, and scatters light or shows refractory distortions, both affecting the observed image. Quantifying the performance of Anti-Fog coated lenses is difficult: they may not show classical fogging and the existing testing methods, based on fog detection, are therefore inapplicable. The presented method for evaluating and quantifying AF properties is based on characterizing light scattering on lenses exposed to controlled humidity and temperature. Changes in intensity of laser light scattered at low angles (1, 2 4 and 8 degrees), observed during condensation of water on lenses, provide information on the swelling of Anti-Fog coatings, formation of uniform water film, going from an unstable to a steady state, and on the coalescence of discontinuous films. Real time observations/measurements allow for better understanding of factors controlling fogging and fog preventing phenomena. The method is especially useful in the development of new coatings for military-, sport-, and industrial protective eyewear as well as for medical and automotive applications. It allows for differentiating between coatings showing acceptable, good, and excellent performance.

  4. Radiation fog and urban climate

    SciTech Connect

    Sachweh, M.; Koepke, P.

    1995-05-01

    Fog data of Southern Germany from the period 1949-1990 indicate a significant urban influence on fog frequency. An increase of the urban building density is connected with a reduction in the average number of fog days, which is interpreted as an effect of the urban heat island and moisture deficit. Feedback mechanisms which intensify the urban-rural contrast are discussed. The results are transferable to large cities with relatively good air quality.

  5. Fog water chemical composition in different geographic regions of Poland

    NASA Astrophysics Data System (ADS)

    Błaś, Marek; Polkowska, Żaneta; Sobik, Mieczysław; Klimaszewska, Kamila; Nowiński, Kamil; Namieśnik, Jacek

    2010-03-01

    The fog water samples were collected with the use of both passive and active fog collectors during 2005-2006 at 3 sites: lowland in northern Poland (Borucino; 186 m a.s.l.), valley basin in southern Poland (Zakopane; 911 m a.s.l.) and mountain top (Szrenica Mt.; 1330 m a.s.l.) in south-western Poland. For all daily samples (Borucino—25; Zakopane—4 and Szrenica—155), electric conductivity, pH, and concentrations of some anions: Cl -, F -, Br -, NO 2-, NO 3-, SO 42-, PO 43-and cations: NH 4+, Ca 2+, K +, Na + and Mg 2+ were measured. The selected ions were determined using ion suppressed chromatography (IC). Fog consists of a specific type of atmospheric phenomena. Results obtained on the basis of analysis of suitable fog samples can be treated as a source of valuable information on the chemistry of the atmosphere. Statistical analysis revealed significant differences depending on region, altitude, local morphology and, last but not least, fog origin. A distinct contrast is evident in the concentration and chemical composition between lowland radiation fog (represents lower layers of the atmosphere which are more influenced by continental emissions) versus orographic slope fog represented by a summit station, Mt Szrenica. It is partly induced by a distinction in weather conditions favouring fog existence, height of fog formation and its microphysical parameters. Acidity was associated with high concentrations of excess sulphate and nitrate in the fog water samples. Ammonium and calcium concentrations represent the most important neutralizing inputs. Collected cloud water at Szrenica Mt. includes solute contributions from emission sources located at much larger upwind distances. The fact that 95% of fog/cloud deposition is concentrated during SW-W-NW-N-NE, atmospheric circulation exerts an influence on the environmental quality of montane forests in the Sudety Mts. At numerous conspicuous convex landforms, where fog/cloud deposition becomes at least as important

  6. Fog-aerosol interactions in the coastal Namib Desert

    NASA Astrophysics Data System (ADS)

    Soderberg, K.; Swap, R. J.; Macko, S. A.

    2009-12-01

    The hyper-arid coastal Namib Desert in southern Africa is characterized by frequent morning fog, which is an important water supply for certain desert organisms. The fog is climatologically driven by both the cool upwelling Benguela Current and the general stability of the lower atmosphere at tropical latitudes. High dimethyl sulfide (DMS) concentrations associated with the productive upwelling zone suggest DMS as the major source of condensation nuclei for fog formation. However, the few available chemical analyses of fog water show a strong relationship between dissolved calcium and sulfur in the fog. A likely source of these ions is the gypsum (CaSO4) crust common across the gravel plains of the Namib. The current study exploits the isotopic difference between sulfur of the gypsum crusts (δ34S = +12‰) and that of marine sulfur (δ34Sseasalt = +20‰, δ34SDMS = +18‰) to determine sources of sulfur in size-segregated aerosols collected before, during, and after a fog event in the Central Namib, 56 km from the coast. Any significant contribution from the relatively infrequent releases of H2S (δ34S = -20‰) from the organic-rich Benguela sediments will also be apparent. A previous study of bulk chemical concentrations in Namib aerosols from the same study area found a biogenic marine signal in the fine fraction (<1 micron), whereas the coarse fraction (>1 micron) had a mixed inorganic marine (sea salt) and terrestrial signature. The implications of the aerosol-fog chemistry relationships are explored, including a possible feedback between aridity and fog formation.

  7. An Observational Case Study of Persistent Fog and Comparison with an Ensemble Forecast Model

    NASA Astrophysics Data System (ADS)

    Price, Jeremy; Porson, Aurore; Lock, Adrian

    2015-05-01

    We present a study of a persistent case of fog and use the observations to evaluate the UK Met Office ensemble model. The fog appeared to form initially in association with small patches of low-level stratus and spread rapidly across southern England during 11 December 2012, persisting for 24 h. The low visibility and occurrence of fog associated with the event was poorly forecast. Observations show that the surprisingly rapid spreading of the layer was due to a circulation at the fog edge, whereby cold cloudy air subsided into and mixed with warmer adjacent clear air. The resulting air was saturated, and hence the fog layer grew rapidly outwards from its edge. Measurements of fog-droplet deposition made overnight show that an average of 12 g m h was deposited but that the liquid water content remained almost constant, indicating that further liquid was condensing at a similar rate to the deposition, most likely due to the slow cooling. The circulation at the fog edge was also present during its dissipation, by which time the fog top had lowered by 150 m. During this period the continuing circulation at the fog edge, and increasing wind shear at fog top, acted to dissipate the fog by creating mixing with, by then, the drier adjacent and overlying air. Comparisons with a new, high resolution Met Office ensemble model show that this type of case remains challenging to simulate. Most ensemble members successfully simulated the formation and persistence of low stratus cloud in the region, but produced too much cloud initially overnight, which created a warm bias. During the daytime, ensemble predictions that had produced fog lifted it into low stratus, whilst in reality the fog remained present all day. Various aspects of the model performance are discussed further.

  8. LAYER DEPENDENT ADVECTION IN CMAQ

    EPA Science Inventory

    The advection methods used in CMAQ require that the Courant-Friedrichs-Lewy (CFL) condition be satisfied for numerical stability and accuracy. In CMAQ prior to version 4.3, the ADVSTEP algorithm established CFL-safe synchronization and advection timesteps that were uniform throu...

  9. Connections Between Cold Air Pools and Mountain Valley Fog Events in Salt Lake City

    NASA Astrophysics Data System (ADS)

    Chachere, Catherine N.; Pu, Zhaoxia

    2016-09-01

    The aim of this study is to investigate the connection between cold air pools and fog events in Salt Lake City, Utah, United States. Statistical analyses are conducted using soundings and reported automated surface observing system data from Salt Lake International Airport for the last eighteen cold seasons (October to March, during 1997-2015). A Chi-square test of independence is performed on identified cold air pool, and fog events to determine whether the two events are correlated. Conditional probabilities are then computed to investigate the occurrence of fog, given the presence of a cold pool. These probabilities are compared against that of random fog generation in the mid-winter. It is concluded that the dependence between cold air pools and fog events is statistically significant. The presence of a cold pool makes the formation of fog more likely than random generation.

  10. Sea Fog Forecasting with Lagrangian Models

    NASA Astrophysics Data System (ADS)

    Lewis, J. M.

    2014-12-01

    In 1913, G. I. Taylor introduced us to a Lagrangian view of sea fog formation. He conducted his study off the coast of Newfoundland in the aftermath of the Titanic disaster. We briefly review Taylor's classic work and then apply these same principles to a case of sea fog formation and dissipation off the coast of California. The resources used in this study consist of: 1) land-based surface and upper-air observations, 2) NDBC (National Data Buoy Center) observations from moored buoys equipped to measure dew point temperature as well as the standard surface observations at sea (wind, sea surface temperature, pressure, and air temperature), 3) satellite observations of cloud, and 4) a one-dimensional (vertically directed) boundary layer model that tracks with the surface air motion and makes use of sophisticated turbulence-radiation parameterizations. Results of the investigation indicate that delicate interplay and interaction between the radiation and turbulence processes makes accurate forecasts of sea fog onset unlikely in the near future. This pessimistic attitude stems from inadequacy of the existing network of observations and uncertainties in modeling dynamical processes within the boundary layer.

  11. Pilot Scale Advanced Fogging Demonstration

    SciTech Connect

    Demmer, Rick L.; Fox, Don T.; Archiblad, Kip E.

    2015-01-01

    Experiments in 2006 developed a useful fog solution using three different chemical constituents. Optimization of the fog recipe and use of commercially available equipment were identified as needs that had not been addressed. During 2012 development work it was noted that low concentrations of the components hampered coverage and drying in the United Kingdom’s National Nuclear Laboratory’s testing much more so than was evident in the 2006 tests. In fiscal year 2014 the Idaho National Laboratory undertook a systematic optimization of the fogging formulation and conducted a non-radioactive, pilot scale demonstration using commercially available fogging equipment. While not as sophisticated as the equipment used in earlier testing, the new approach is much less expensive and readily available for smaller scale operations. Pilot scale testing was important to validate new equipment of an appropriate scale, optimize the chemistry of the fogging solution, and to realize the conceptual approach.

  12. Advances in fog microphysics research in China

    NASA Astrophysics Data System (ADS)

    Liu, Duanyang; Li, Zihua; Yan, Wenlian; Li, Yi

    2017-02-01

    Fog microphysical research in China based on field experiments obtained many important results in recent 50 years. With the fast development of China's economy, urbanization in the last 30 years, special features of fog microphysical structure also appeared, which did not appear in other countries. This article reviews the fog microphysical research around China, and introduces the effect of urbanization on fog microphysical structure and the microphysical processes as well as macroscopic conditions of radiation fog droplet spectral broadening. Urbanization led to an increase in fog droplet number concentration but decreases in fog liquid water content (LWC) and fog droplet size, as well as a decrease in visibility in large cities. Observations show that the radiation fog could be divided into wide-spectrum one, which is all extremely dense fog with the spectral width more than 40 μm, and narrow-spectrum one, most of which is dense fog with the spectral width less than 22 μm, according to droplet spectral distribution. During developing from dense fog to extremely dense fog, the widespectrum radiation fog is characterized by explosive deepening, that is, within a very short time (about 30 min), the droplet concentration increase by about one order of magnitude, droplet spectral broadening across 20 μm, generally up to 30-40 μm, or even 50 μm. As a result, water content increased obviously, visibility decreased to less than 50 m, when dense fog became extremely dense fog.

  13. Rain, fog, and clouds for aircraft simulators

    NASA Technical Reports Server (NTRS)

    Chase, W. D.

    1981-01-01

    Environmental chamber creates realistic fog and rain effects in aircraft simulator. It reproduces clouds, homogeneous fog, patches of fog, rain and fog, and rain only. It is used with real time digital computer, color computer generated image display that simulates airport lights, or color television camera that produces moving display of airport runway as depicted on model terrain board.

  14. Quantity of acid in acid fog

    SciTech Connect

    Deal, W.J.

    1983-07-01

    The chemical composition of fog particles has become of considerable interest, because of both the possibility of interpreting atmospheric- chemistry processes in fog particles in terms of the principles of aqueous chemistry and the potential health effects of species present in fog particles. The acidity of fog particles has received wide attention. This communication noted the actual magnitude of the excess acidity in acidic fog particles and suggested a possible line of inquiry into the health effects of such fog so that it can be determined whether a typical fog is detrimental or beneficial relative to dry air. (DP)

  15. Fog research in China: An overview

    NASA Astrophysics Data System (ADS)

    Niu, Shengjie; Lu, Chunsong; Yu, Huaying; Zhao, Lijuan; Lü, Jingjing

    2010-05-01

    Fog can adversely affect human activity directly and indirectly, resulting in large losses both in terms of the local economy and lives. Much effort has been devoted to studies of fog across many areas of China, and in that context this paper aims to summarize climatic characteristics and review fog field experiments and their major results relating to fog mechanisms, physical properties and chemical characteristics. Progress in the application of remote sensing techniques and numerical simulation in fog research are also discussed. In particular, the effects of urbanization and industrialization on fog are highlighted. To end, perspectives on future fog research are outlined. The goal of this review paper is to introduce fog research in China to the global academic community and thus promote international collaboration on fog research. This is important because most papers on fog in China are published in Chinese, which are unreadable for the vast majority of non-Chinese researchers.

  16. Fog dispersion. [charged particle technique

    NASA Technical Reports Server (NTRS)

    Christensen, L. S.; Frost, W.

    1980-01-01

    The concept of using the charged particle technique to disperse warm fog at airports is investigated and compared with other techniques. The charged particle technique shows potential for warm fog dispersal, but experimental verification of several significant parameters, such as particle mobility and charge density, is needed. Seeding and helicopter downwash techniques are also effective for warm fog disperals, but presently are not believed to be viable techniques for routine airport operations. Thermal systems are currently used at a few overseas airports; however, they are expensive and pose potential environmental problems.

  17. The Challenge of Forecasting the Onset and Development of Radiation Fog Using Mesoscale Atmospheric Models

    NASA Astrophysics Data System (ADS)

    Steeneveld, G. J.; Ronda, R. J.; Holtslag, A. A. M.

    2015-02-01

    The numerical weather prediction of radiation fog is challenging, as many models typically show large biases for the timing of the onset and dispersal of the fog, as well as for its depth and liquid water content. To understand the role of physical processes, i.e. turbulence, radiation, land-surface coupling, and microphysics, we evaluate the HARMONIE and Weather Research and Forecasting (WRF) mesoscale models for two contrasting warm fog episodes at the relatively flat terrain around the Cabauw tower facility in the Netherlands. One case involves a radiation fog that arose in calm anticyclonic conditions, and the second is a radiation fog that developed just after a cold front passage. The WRF model represents the radiation fog well, while the HARMONIE model forecasts a stratus lowering fog layer in the first case and hardly any fog in the second case. Permutations of parametrization schemes for boundary-layer mixing, radiation and microphysics, each for two levels of complexity, have been evaluated within the WRF model. It appears that the boundary-layer formulation is critical for forecasting the fog onset, while for fog dispersal the choice of the microphysical scheme is a key element, where a double-moment scheme outperforms any of the single-moment schemes. Finally, the WRF model results appear to be relatively insensitive to horizontal grid spacing, but nesting deteriorates the modelled fog formation. Increasing the domain size leads to a more scattered character of the simulated fog. Model results with one-way or two-way nesting show approximately comparable results.

  18. Integration of Local Observations into the One Dimensional Fog Model PAFOG

    NASA Astrophysics Data System (ADS)

    Thoma, Christina; Schneider, Werner; Masbou, Matthieu; Bott, Andreas

    2012-05-01

    The numerical prediction of fog requires a very high vertical resolution of the atmosphere. Owing to a prohibitive computational effort of high resolution three dimensional models, operational fog forecast is usually done by means of one dimensional fog models. An important condition for a successful fog forecast with one dimensional models consists of the proper integration of observational data into the numerical simulations. The goal of the present study is to introduce new methods for the consideration of these data in the one dimensional radiation fog model PAFOG. First, it will be shown how PAFOG may be initialized with observed visibilities. Second, a nudging scheme will be presented for the inclusion of measured temperature and humidity profiles in the PAFOG simulations. The new features of PAFOG have been tested by comparing the model results with observations of the German Meteorological Service. A case study will be presented that reveals the importance of including local observations in the model calculations. Numerical results obtained with the modified PAFOG model show a distinct improvement of fog forecasts regarding the times of fog formation, dissipation as well as the vertical extent of the investigated fog events. However, model results also reveal that a further improvement of PAFOG might be possible if several empirical model parameters are optimized. This tuning can only be realized by comprehensive comparisons of model simulations with corresponding fog observations.

  19. Textbook Selection: Clearing the Fog.

    ERIC Educational Resources Information Center

    Hollabaugh, Mark

    1989-01-01

    Provides step-by-step procedures for developing an index which uses the Gunning Fog technique to evaluate the level of reading difficulty of textbooks. Cites examples, illustrations, and several warnings in the discussion. (RT)

  20. FOGCAST: Probabilistic fog forecasting based on operational (high-resolution) NWP models

    NASA Astrophysics Data System (ADS)

    Masbou, M.; Hacker, M.; Bentzien, S.

    2013-12-01

    The presence of fog and low clouds in the lower atmosphere can have a critical impact on both airborne and ground transports and is often connected with serious accidents. The improvement of localization, duration and variations in visibility therefore holds an immense operational value. Fog is generally a small scale phenomenon and mostly affected by local advective transport, radiation, turbulent mixing at the surface as well as its microphysical structure. Sophisticated three-dimensional fog models, based on advanced microphysical parameterization schemes and high vertical resolution, have been already developed and give promising results. Nevertheless, the computational time is beyond the range of an operational setup. Therefore, mesoscale numerical weather prediction models are generally used for forecasting all kinds of weather situations. In spite of numerous improvements, a large uncertainty of small scale weather events inherent in deterministic prediction cannot be evaluated adequately. Probabilistic guidance is necessary to assess these uncertainties and give reliable forecasts. In this study, fog forecasts are obtained by a diagnosis scheme similar to Fog Stability Index (FSI) based on COSMO-DE model outputs. COSMO-DE I the German-focused high-resolution operational weather prediction model of the German Meteorological Service. The FSI and the respective fog occurrence probability is optimized and calibrated with statistical postprocessing in terms of logistic regression. In a second step, the predictor number of the FOGCAST model has been optimized by use of the LASSO-method (Least Absolute Shrinkage and Selection Operator). The results will present objective out-of-sample verification based on the Brier score and is performed for station data over Germany. Furthermore, the probabilistic fog forecast approach, FOGCAST, serves as a benchmark for the evaluation of more sophisticated 3D fog models. Several versions have been set up based on different

  1. Fog water chemistry in Shanghai

    NASA Astrophysics Data System (ADS)

    Li, Pengfei; Li, Xiang; Yang, Chenyu; Wang, Xinjun; Chen, Jianmin; Collett, Jeffrey L., Jr.

    2011-08-01

    With the aim of understanding the fog chemistry in a Chinese megacity, twenty-six fog water samples were collected in urban Shanghai from March 2009 to March 2010. The following parameters were measured: pH, electrical conductivity (EC), ten inorganic major ions ( SO42-, NO3-, NO2-, F -, Cl -, Na +, K +, Ca 2+, Mg 2+, NH4+) and four major organic acids (CH 3COO -, HCOO -, CO42-, MSA). The total ionic concentration (TIC) and EC of fog samples were one or two orders of magnitude higher than those often found in Europe, North America and other Asian countries. Pollutants were expected to be mainly from local sources, including factories, motor vehicle emissions and civil construction. Non-local sources such as moderate- and long-range transport of sea salt also contributed to pollution levels in fog events as indicated by back trajectory analysis. The pH of the fog water collected during the monitoring period varied from 4.68 to 6.58; acidic fogs represented about 30.8% of the total fog events during this period. The fog water was characterized by high concentrations of SO42- (20.0% of measured TIC), NO3- (17.1%), NH4+ (28.3%) and Ca 2+ (14.4%). SO42- and NO3-, the main precursors of fog acidity, were related to burning fossil fuels and vehicle emissions, respectively. NH4+, originating from the scavenging of gaseous ammonia and particulate ammonium nitrate and ammonium sulfate, and Ca 2+, originating from the scavenging of coarse particles, acted as acid neutralizers and were the main cause for the relatively high pH of fogs in Shanghai. The ratio of ( SO42- + NO3-)/( NH4+ + Ca 2+) was lower than 1, indicating the alkaline nature of the fog water. A high ratio of NO3-/ SO42- and low ratio of HCOO -/CH 3COO - were consistent with large contributions from vehicular emissions that produce severe air pollution in megacities.

  2. An assessment of acid fog

    SciTech Connect

    Lipfert, F.W.

    1992-12-31

    Airborne particles have long been associated with adverse effects on public health, begin with the notorious air pollution disasters of several decades ago. Although H{sub 2}SO{sub 4} was identified early on as a potential causal factors during these episodes (in part because of concern for potential health effects of particle acidity per se has intensified only recently. Most of the recent aerometric research in the US on acid fog has focused on the ability of clouds and fog to deliver acidity to vegetation and ecosystems. Strong acids are characterized chemically by their pH or H{sup +} concentration. For fog, concentrations are referred to the droplet liquid content; for other (i.e., ``clear air``) aerosols, to the volume of air sampled. A useful measure of the relationship between aerosol and fog is obtained by comparing their mass concentrations on the basis of the same volume of air, by multiplying fogwater concentrations by liquid water content (LWC). This paper reviews fog measurement capability, physical properties and chemistry, and presents a simple urban airshed model which is used to simulate the evolution of fog and aerosol concentrations under urban stagnation conditions.

  3. Particulate contribution to extinction of visible radiation: Pollution, haze, and fog

    NASA Astrophysics Data System (ADS)

    Elias, Thierry; Haeffelin, Martial; Drobinski, Philippe; Gomes, Laurent; Rangognio, Jerome; Bergot, Thierry; Chazette, Patrick; Raut, Jean-Christophe; Colomb, Michèle

    2009-06-01

    A data set acquired by eight particle-dedicated instruments set up on the SIRTA (Site Instrumental de Recherche par Télédétection Atmosphérique, which is French for Instrumented Site for Atmospheric Remote Sensing Research) during the ParisFog field campaign are exploited to document microphysical properties of particles contributing to extinction of visible radiation in variable situations. The study focuses on a 48-hour period when atmospheric conditions are highly variable: relative humidity changes between 50 and 100%, visibility ranges between 65 and 35 000 m, the site is either downwind the Paris area either under maritime influence. A dense and homogeneous fog formed during the night by radiative cooling. In 6 h, visibility decreased down from 30 000 m in the clear-sky regime to 65 m within the fog, because of advected urban pollution (factor 3 to 4 in visibility reduction), aerosol hydration (factor 20) and aerosol activation (factor 6). Computations of aerosol optical properties, based on Mie theory, show that extinction in clear-sky regime is due equally to the ultrafine modes and to the accumulation mode. Extinction by haze is due to hydrated aerosol particles distributed in the accumulation mode, defined by a geometric mean diameter of 0.6 μm and a geometric standard deviation of 1.4. These hydrated aerosol particles still contribute by 20 ± 10% to extinction in the fog. The complementary extinction is due to fog droplets distributed around the geometric mean diameter of 3.2 μm with a geometric standard deviation of 1.5 during the first fog development stage. The study also shows that the experimental set-up could not count all fog droplets during the second and third fog development stages.

  4. Numerical simulation of radiation fog in complex terrain

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Musson-Genon, L.; Carissimo, B.; Dupont, E.

    2009-09-01

    The interest for micro-scale modeling of the atmosphere is growing for environmental applications related, for example, to energy production, transport and urban development. The turbulence in the stable layers where pollutant dispersion is low and can lead to strong pollution events. This could be further complicated by the presence of clouds or fog and is specifically difficult in urban or industrial area due to the presence of buildings. In this context, radiation fog formation and dissipation over complex terrain were therefore investigated with a state-of-the-art model. This study is divided into two phases. The first phase is a pilot stage, which consist of employing a database from the ParisFog campaign which took place in the south of Paris during winter 2006-07 to assess the ability of the cloud model to reproduce the detailed structure of radiation fog. The second phase use the validated model for the study of influence of complex terrain on fog evolution. Special attention is given to the detailed and complete simulations and validation technique used is to compare the simulated results using the 3D cloud model of computational fluid dynamical software Code_Saturne with one of the best collected in situ data during the ParisFog campaign. Several dynamical, microphysical parameterizations and simulation conditions have been described. The resulting 3D cloud model runs at a horizontal resolution of 30 m and a vertical resolution comparable to the 1D model. First results look very promising and are able to reproduce the spatial distribution of fog. The analysis of the behavior of the different parameterized physical processes suggests that the subtle balance between the various processes is achieved.

  5. Numerical forecasting of radiation fog. Part I: Numerical model and sensitivity tests

    SciTech Connect

    Bergot, T.; Guedalia, D. )

    1994-06-01

    To improve the forecast of dense radiative fogs, a method has been developed using a one-dimensional model of the nocturnal boundary layer forced by the mesoscale fields provided by a 3D limited-area operational model. The 1D model involves a treatment of soil-atmosphere exchanges and a parameterization of turbulence in stable layers in order to correctly simulate the nocturnal atmospheric cooling. Various sensitivity tests have been carried out to evaluate the influence of the main input parameters of the model (geostrophic wind, horizontal advections, cloud cover, soil moisture, etc.) on the predicted fog characteristics. The principal result concerns the difficulty of obtaining accurate forecasts in the case of fog appearing in the middle or at the end of the night, when the local atmospheric cooling is weak. 33 refs., 13 figs.

  6. High Order Semi-Lagrangian Advection Scheme

    NASA Astrophysics Data System (ADS)

    Malaga, Carlos; Mandujano, Francisco; Becerra, Julian

    2014-11-01

    In most fluid phenomena, advection plays an important roll. A numerical scheme capable of making quantitative predictions and simulations must compute correctly the advection terms appearing in the equations governing fluid flow. Here we present a high order forward semi-Lagrangian numerical scheme specifically tailored to compute material derivatives. The scheme relies on the geometrical interpretation of material derivatives to compute the time evolution of fields on grids that deform with the material fluid domain, an interpolating procedure of arbitrary order that preserves the moments of the interpolated distributions, and a nonlinear mapping strategy to perform interpolations between undeformed and deformed grids. Additionally, a discontinuity criterion was implemented to deal with discontinuous fields and shocks. Tests of pure advection, shock formation and nonlinear phenomena are presented to show performance and convergence of the scheme. The high computational cost is considerably reduced when implemented on massively parallel architectures found in graphic cards. The authors acknowledge funding from Fondo Sectorial CONACYT-SENER Grant Number 42536 (DGAJ-SPI-34-170412-217).

  7. C. elegans FOG-3/Tob can either promote or inhibit germline proliferation, depending on gene dosage and genetic context.

    PubMed

    Snow, J J; Lee, M-H; Verheyden, J; Kroll-Conner, P L; Kimble, J

    2013-05-23

    Vertebrate Tob/BTG proteins inhibit cell proliferation when overexpressed in tissue-culture cells, and they can function as tumor suppressors in mice. The single Caenorhabditis elegans Tob/BTG ortholog, FOG-3, by contrast, was identified from its loss-of-function phenotype as a regulator of sperm fate specification. Here we report that FOG-3 also regulates proliferation in the germline tissue. We first demonstrate that FOG-3 is a positive regulator of germline proliferation. Thus, fog-3 null mutants possess fewer germ cells than normal, a modest but reproducible decrease observed for each of two distinct fog-3 null alleles. A similar decrease also occurred in fog-3/+ heterozygotes, again for both fog-3 alleles, revealing a haplo-insufficient effect on proliferation. Therefore, FOG-3 normally promotes proliferation, and two copies of the fog-3 gene are required for this function. We next overexpressed FOG-3 by removal of FBF, the collective term for FBF-1 and FBF-2, two nearly identical PUF RNA-binding proteins. We find that overexpressed FOG-3 blocks proliferation in fbf-1 fbf-2 mutants; whereas germ cells stop dividing and instead differentiate in fbf-1 fbf-2 double mutants, they continue to proliferate in fog-3; fbf-1 fbf-2 triple mutants. Therefore, like its vertebrate Tob/BTG cousins, overexpressed FOG-3 is 'antiproliferative'. Indeed, some fog-3; fbf-1 fbf-2 mutants possess small tumors, suggesting that FOG-3 can act as a tumor suppressor. Finally, we show that FOG-3 and FBF work together to promote tumor formation in animals carrying oncogenic Notch mutations. A similar effect was not observed when germline tumors were induced by manipulation of other regulators; therefore, this FOG-3 tumor-promoting effect is context dependent. We conclude that FOG-3 can either promote or inhibit proliferation in a manner that is sensitive to both genetic context and gene dosage. The discovery of these FOG-3 effects on proliferation has implications for our understanding of

  8. Broad-spectrum monitoring strategies for predicting occult precipitation contribution to water balance in a coastal watershed in California: Ground-truthing, areal monitoring and isotopic analysis of fog in the San Francisco Bay region

    NASA Astrophysics Data System (ADS)

    Koohafkan, M.; Thompson, S. E.; Leonardson, R.; Dufour, A.

    2013-12-01

    We showcase a fog monitoring study designed to quantitatively estimate the contribution of summer fog events to the water balance of a coastal watershed managed by the San Francisco Public Utilities Commission. Two decades of research now clearly show that fog and occult precipitation can be major contributors to the water balance of watersheds worldwide. Monitoring, understanding and predicting occult precipitation is therefore as hydrologically compelling as forecasting precipitation or evaporation, particularly in the face of climate variability. We combine ground-based monitoring and collection strategies with remote sensing technologies, time-lapse imagery, and isotope analysis to trace the ';signature' of fog in physical and ecological processes. Spatial coverage and duration of fog events in the watershed is monitored using time-lapse cameras and leaf wetness sensors strategically positioned to provide estimates of the fog bank extent and cloud base elevation, and this fine-scale data is used to estimate transpiration suppression by fog and is examined in the context of regional climate through the use of satellite imagery. Soil moisture sensors, throughfall collectors and advective fog collectors deployed throughout the watershed provide quantitative estimates of fog drip contribution to soil moisture and plants. Fog incidence records and streamflow monitoring provide daily estimates of fog contribution to streamflow. Isotope analysis of soil water, fog drip, stream water and vegetation samples are used to probe for evidence of direct root and leaf uptake of fog drip by plants. Using this diversity of fog monitoring methods, we develop an empirical framework for the inclusion of fog processes in water balance models.

  9. Diurnal temperature asymmetries and fog at Churchill, Manitoba

    NASA Astrophysics Data System (ADS)

    Gough, William A.; He, Dianze

    2015-07-01

    A variety of methods are available to calculate daily mean temperature. We explore how the difference between two commonly used methods provides insight into the local climate of Churchill, Manitoba. In particular, we found that these differences related closely to seasonal fog. A strong statistically significant correlation was found between the fog frequency (hours per day) and the diurnal temperature asymmetries of the surface temperature using the difference between the min/max and 24-h methods of daily temperature calculation. The relationship was particularly strong for winter, spring and summer. Autumn appears to experience the joint effect of fog formation and the radiative effect of snow cover. The results of this study suggests that subtle variations of diurnality of temperature, as measured in the difference of the two mean temperature methods of calculation, may be used as a proxy for fog detection in the Hudson Bay region. These results also provide a cautionary note for the spatial analysis of mean temperatures using data derived from the two different methods particularly in areas that are fog prone.

  10. A Satellite Based Fog Study of the Korean Peninsula

    DTIC Science & Technology

    2007-06-01

    worksheets (see an example in Figure 8), which were excel spreadsheets formatted as a guideline used by forecasters when preparing their terminal...of the forecasts worksheets used by forecasters attached to the 607th Weather Squadron, Korea...accuracy was considered questionable by some meteorologists. The Kim and Lee (1970) study created a worksheet with the number of mean fog days per month

  11. Enhanced extinction of visible radiation due to hydrated aerosols in mist and fog

    NASA Astrophysics Data System (ADS)

    Elias, T.; Dupont, J.-C.; Hammer, E.; Hoyle, C. R.; Haeffelin, M.; Burnet, F.; Jolivet, D.

    2015-06-01

    The study assesses the contribution of aerosols to the extinction of visible radiation in the mist-fog-mist cycle. Relative humidity is large in the mist-fog-mist cycle, and aerosols most efficient in interacting with visible radiation are hydrated and compose the accumulation mode. Measurements of the microphysical and optical properties of these hydrated aerosols with diameters larger than 0.4 μm were carried out near Paris, during November 2011, under ambient conditions. Eleven mist-fog-mist cycles were observed, with a cumulated fog duration of 96 h, and a cumulated mist-fog-mist cycle duration of 240 h. In mist, aerosols grew by taking up water at relative humidities larger than 93%, causing a visibility decrease below 5 km. While visibility decreased down from 5 to a few kilometres, the mean size of the hydrated aerosols increased, and their number concentration (Nha) increased from approximately 160 to approximately 600 cm-3. When fog formed, droplets became the strongest contributors to visible radiation extinction, and liquid water content (LWC) increased beyond 7 mg m-3. Hydrated aerosols of the accumulation mode co-existed with droplets, as interstitial non-activated aerosols. Their size continued to increase, and some aerosols achieved diameters larger than 2.5 μm. The mean transition diameter between the aerosol accumulation mode and the small droplet mode was 4.0 ± 1.1 μm. Nha also increased on average by 60 % after fog formation. Consequently, the mean contribution to extinction in fog was 20 ± 15% from hydrated aerosols smaller than 2.5 μm and 6 ± 7% from larger aerosols. The standard deviation was large because of the large variability of Nha in fog, which could be smaller than in mist or 3 times larger. The particle extinction coefficient in fog can be computed as the sum of a droplet component and an aerosol component, which can be approximated by 3.5 Nha (Nha in cm-3 and particle extinction coefficient in Mm-1. We observed an influence of

  12. In situ detection of the chemistry of individual fog droplet residues in the Pearl River Delta region, China

    NASA Astrophysics Data System (ADS)

    Bi, Xinhui; Lin, Qinhao; Peng, Long; Zhang, Guohua; Wang, Xinming; Brechtel, Fred J.; Chen, Duohong; Li, Mei; Peng, Ping'an; Sheng, Guoying; Zhou, Zhen

    2016-08-01

    We use a single-particle aerosol mass spectrometer coupled with a ground-based counterflow virtual impactor to measure the chemical compositions of individual submicron fog droplet residues. This is the first report on single particle mass spectrometry measurements of fog droplet residual particles at ground level in an urban area. We show that most of the fog droplet residues were composed of elemental carbon (EC) (67.7%), followed by K-rich (19.2%) and mineral dust/metal (12.3%) particles. The predominance of EC-containing particles demonstrated that these particles could be effective fog nuclei and highlights the important influence of anthropogenic emissions on regional climate system. Compared with interstitial and ambient aerosols, nitrate was enhanced, sulfate was depressed, and ammonium- and organics-containing particles were hardly found in the fog droplet residues during fog events, suggesting that dust and metal particles containing nitrate may be preferentially activated and that ammonium and organics may not play important roles in fog formation in Guangzhou. We also present direct observational evidence that trimethylamine and hydroxymethanesulfonate are not found within fog droplet residues, although we previously observed enhanced gas-to-particle partitioning of these compounds by fog processing. Additionally, higher fraction or intensities of [K]+, [Fe]+, and [SiO3]- were found in fog droplet residues than in ambient and interstitial particles.

  13. Low Visibility Formation and Forecasting on the Northern Coast of Brazil

    NASA Astrophysics Data System (ADS)

    Fedorova, Natalia; Levit, Vladimir; da Silva, Aliton Oliveira; dos Santos, Deydila Michele Bonfim

    2013-04-01

    Visibility analysis and forecast at the Maceio International Airport in the Brazilian Northeast (NEB) was the principal goal of this investigation. Surface meteorological data of the Maceio International Airport were used for low visibility frequency study. Low visibility in NEB was provoked more frequently by light fog (LF) formation (1,098 or 92 h month-1 on average). Haze and fog were very rare (81 h and one event per year, respectively on average). Light fog with a visibility less than 2 km usually was detected together with rain or drizzle. Low visibility was observed more frequently at night and during the rainy season. Applications of the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model for light fog forecast were tested. Thermodynamic processes were studied by vertical profile, elaborated by: (1) National Centers for Environmental Prediction (NCEP) reanalysis data for Maceio (because of some radiosonde absence) and (2) forecast vertical temperature and humidity profiles were produced, using Air Parcels Trajectories of the HYSPLIT model at the pattern levels. The synoptic situations before and during low visibility phenomena were analyzed using different products of NCEP reanalysis, the high resolution (10 km) ETA model and infrared satellite images. Wave disturbance in the trade winds field, localized on the northwest periphery of the South Atlantic subtropical High, usually accompanied the phenomena. A humidity advection, weak ascendant movement and thermal inversion absence at the low levels were created by these waves. The middle level's descendent movement provoked the humidity accumulation at levels below. Satisfactory results of the HYSPLIT model applications for light fog forecast were obtained with 12 h antecedence. In particular, stable level forecast by the ETA model was forecast satisfactorily with 12 h antecedence; vertical movements were predicted better with up to 48 h antecedence. The PSU/NCAR mesoscale model (MM5) and

  14. Satellite observations of fog over Indo-Gangetic Plains and its influence on solar irradiance

    NASA Astrophysics Data System (ADS)

    Kharol, Shailesh Kumar; Rani Sharma, Anu; Kvs, Badarinath; Roy, P. S.

    Every year, the Northern region of India, especially the Indo-Gangetic Plains (IGPs) region ex-perience severe fog conditions during winter season due to typical meteorological, environmental and prevailing terrain conditions. The IGP region is highly influenced by western disturbances during winter season, which provide ideal conditions for accumulation of pollutants within the boundary layer and often results in fog formation. The formation of fog over IGPs is believed to create numerous health hazards, economic loss and cross-country transportation of aerosols. The fog is also expected to have impact on agriculture, general economy, global and regional climate. It has attracted the global scientific community attention to address the uncertainties pertaining to its formation and physico-chemical properties. The increase in aerosol concen-tration in the lower atmosphere due to biomass-burning events and anthropogenic activities provides more fog formation with water vapor present in atmosphere over IGP region. In the present study, we made an attempt to study the fog conditions that occurred over North In-dian region and long range transport of aerosols from fog region towards southern region during November, 2008 using multi-satellite data sets and ground based observations on aerosol prop-erties and solar irradiance at urban region of Hyderabad, India. False Color Composites (FCC) of IRS-P6 AWiFS, IRS-P4 OCM and Terra/Aqua MODIS images showed an intense fog/aerosol layer over IGP region on 07th -09th November, 2008. The Terra/Aqua MODIS AOD500 and OMI-AI observations showed high values over IGP region due to fog layer and long range trans-port of aerosols from IGP to Southern Indian region. CALIPSO LIDAR observation showed thick layer of fog/aerosols up to above northern/central Indian region with thickness ranging from 1.5 to 3 Kms. NCEP temperature anomaly variation at 700 hPa showed higher values over IGP region attributed upper atmospheric heating due to

  15. Coastal Fog As a System: Defining an Interdisciplinary Research Agenda (Invited)

    NASA Astrophysics Data System (ADS)

    Weathers, K. C.

    2013-12-01

    Fog is a graphic and charismatic phenomenon that is commonplace in coastal geographies around the globe. Some of the first concerns about fog and human health arose over 50 years ago in foggy cities around the world, such as London and Los Angeles, where thousands of excess deaths have been attributed to the presence of acidic fog particles. Further, the mere presence of fog also results in airplane, ship, and automobile traffic delays and accidents, especially in coastal areas. In many Pacific coastal systems, fog is the primary--sometimes the only--source of water, it is a fundamental moderator of local and regional climate, and it influences productivity of near-coast ecosystems. In recent years fog has been identified as a vector for limiting nutrients (e.g., nitrogen and phosphorus), pollutants (e.g., mercury), and microbes (including human pathogens), all of whose origin is thought to be biologically controlled in the ocean. Researchers have also started inquiring into the importance of fog in modulating weather as well as local, regional and, global climate dynamics. However, from its formation in marine systems to deposition in terrestrial systems, understanding the fog system is an intellectual and interdisciplinary challenge that, to date, has gone unmet. This is in part because the fog system is complex: it involves feedbacks and coupling between physical, chemical, and biological systems in the ocean, atmosphere, and near-coast terrestrial systems. In addition, its formation is the result of global processes, yet its distribution as well as its impacts are local, and extremely spatially and temporally heterogeneous within and across landscapes. Here we describe a systems approach and framework for understanding the controls on fog formation as well as feedbacks to its formation, dissipation, distribution, flows, and stocks or pools. In addition, an interdisciplinary research agenda for coastal fog as a system will be described based on the outcome of a

  16. Quantity of acid in acid fog

    SciTech Connect

    Deal, W.J.

    1983-07-01

    This communication notes the actual magnitude of the acidity in acidic fog particles and suggests a possible line of inquiry into the health effects of such fog so that it can be determined whether a typical fog is detrimental or beneficial relative to dry air.

  17. 33 CFR 118.130 - Fog signals.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Fog signals. 118.130 Section 118... LIGHTING AND OTHER SIGNALS § 118.130 Fog signals. On waterways where visibility is frequently reduced due to fog or other causes, the District Commander may require or authorize the installation of one...

  18. 33 CFR 118.130 - Fog signals.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Fog signals. 118.130 Section 118... LIGHTING AND OTHER SIGNALS § 118.130 Fog signals. On waterways where visibility is frequently reduced due to fog or other causes, the District Commander may require or authorize the installation of one...

  19. Dimethyl Mercury in Seawater: a Potential Source of Monomethyl Mercury in Fog

    NASA Astrophysics Data System (ADS)

    Coale, K. H.; Heim, W. A.; Olson, A.; Chiswell, H.; Byington, A.; Newman, A.; Bonnema, A.; Johnson, M.; Fernandez, D.; Weiss-Penzias, P. S.; Parker, C.

    2015-12-01

    Our collaborative studies show that maritime advective fog transports monomethyl mercury (MMHg) from the oceans to land where terrestrial biota accumulate this neurotoxin to high levels. To date the source of MMHg and the mechanism of this cycling remain unknown. We show that the rate of gaseous evasion of dimethyl mercury (DMHg) is fairly large. Vertical gradients of dimethyl mercury (DMHg) from cyclonic eddies in the California Current indicate an evasive loss of this compound of over 10 pmol m-2 d-1 from these and other upwelling systems. Previous experiments, however, indicated that the rate of photolytic demethylation of DMHg to MMHg is extremely slow in seawater. In this study we performed photodemethylation experiments in both natural seawater and seawater acidified to pH = 5 (the pH of fog). These results confirm the low rates of photodemethylation of DMHg previously observed, yet also show that photodemethylation is a significant factor in the demethylation of DMHg at low pH and thus a potential source of MMHg in fog. These findings suggest photodemethylation may occur atmospherically, and may explain both the high concentrations of MMHg found in fog, and the difference in concentrations of MMHg found in fog water vs rainwater.

  20. Enhanced extinction of visible radiation due to hydrated aerosols in mist and fog

    NASA Astrophysics Data System (ADS)

    Elias, T.; Dupont, J.-C.; Hammer, E.; Hoyle, C. R.; Haeffelin, M.; Burnet, F.; Jolivet, D.

    2015-01-01

    The study assesses the contribution of aerosols to the extinction of visible radiation in the mist-fog-mist cycle. Measurements of the microphysical and optical properties of hydrated aerosols with diameters larger than 400 nm, composing the accumulation mode, which are the most efficient to interact with visible radiation, were carried out near Paris, during November 2011, in ambient conditions. Eleven mist-fog-mist cycles were observed, with cumulated fog duration of 95 h, and cumulated mist-fog-mist duration of 240 h. In mist, aerosols grew up by taking up water at relative humidities larger than 93%, causing a visibility decrease below 5 km. While visibility decreased down to few km, the mean size of the hydrated aerosols increased, and their number concentration (Nha) increased from approximately 160 to approximately 600 cm-3. When fog formed, droplets became the strongest contributors to visible radiation extinction, and liquid water content (LWC) increased beyond 7 mg m-3. Hydrated aerosols of the accumulation mode co-existed with droplets, as interstitial non-activated aerosols. Their size continued to increase, and a significant proportion of aerosols achieved diameters larger than 2.5 μm. The mean transition diameter between the accumulation mode and the small droplet mode was 4.0 ± 1.1 μm. Moreover Nha increased on average by 60% after fog formation. Consequently the mean aerosol contribution to extinction in fog was 20 ± 15% for diameter smaller than 2.5 μm and 6 ± 7% beyond. The standard deviation is large because of the large variability of Nha in fog, which could be smaller than in mist or three times larger. The particle extinction coefficient in fog can be computed as the sum of a droplet component and an aerosol component, which can be approximated by 3.5 Nha (Nha in cm-3 and particle extinction coefficient in Mm-1). We observed an influence of the main formation process on Nha, but not on the contribution to fog extinction by aerosols

  1. Significant concentration changes of chemical components of PM1 in the Yangtze River Delta area of China and the implications for the formation mechanism of heavy haze-fog pollution.

    PubMed

    Zhang, Y W; Zhang, X Y; Zhang, Y M; Shen, X J; Sun, J Y; Ma, Q L; Yu, X M; Zhu, J L; Zhang, L; Che, H C

    2015-12-15

    Since the winter season of 2013, a number of persistent haze-fog events have occurred in central-eastern China. Continuous measurements of the chemical and physical properties of PM1 at a regional background station in the Yangtze River Delta area of China from 16 Nov. to 18 Dec., 2013 revealed several haze-fog events, among which a heavy haze-fog event occurred between 6 Dec. and 8 Dec. The mean concentration of PM1 was 212μgm(-3) in the heavy haze-fog period, which was about 10 times higher than on clean days and featured a peak mass concentration that reached 298μgm(-3). Organics were the largest contributor to the dramatic rise of PM1 on heavy haze-fog days (average mass concentration of 86μgm(-3)), followed by nitrate (58μgm(-3)), sulfate (35μgm(-3)), ammonium (29μgm(-3)), and chloride (4.0μgm(-3)). Nitrate exhibited the largest increase (~20 factors), associated with a significant increase in NOx. This was mainly attributable to increased coal combustion emissions, relative to motor vehicle emissions, and was caused by short-distance pollutant transport within surrounding areas. Low-volatility oxidized organic aerosols (OA) (LV-OOA) and biomass-burning OA (BBOA) also increased sharply on heavy haze-fog days, exhibiting an enhanced oxidation capacity of the atmosphere and increased emissions from biomass burning. The strengthening of the oxidation capacity during the heavy pollution episode, along with lower solar radiation, was probably due to increased biomass burning, which were important precursors of O3. The prevailing meteorological conditions, including low wind and high relative humidity, and short distance transported gaseous and particulate matter surrounding of the sampling site, coincided with the increased pollutant concentrations mainly from biomass-burning mentioned above to cause the persistent haze-fog event in the YRD area.

  2. Fog collectors and collection techniques

    NASA Astrophysics Data System (ADS)

    Höhler, I.; Suau, C.

    2010-07-01

    The earth sciences taught that due to the occurrence of water in three phases: gas, liquid and solid, solar energy keeps the hydrological cycle going, shaping the earth surface while regulating the climate and thus allowing smart technologies to interfere in the natural process by rerouting water and employing its yield for natural and human environments’ subsistence. This is the case of traditional fog collectors implemented by several researchers along the Atacama Desert since late ’50s such as vertical tensile mesh or macro-diamonds structures. Nevertheless, these basic prototypes require to be upgraded, mainly through new shapes, fabrics and frameworks’ types by following the principles of lightness, transformability, portability and polyvalence. The vertical canvas of conventional fog collectors contain too much stressed at each joints and as result it became vulnerable. Our study constitutes a research by design of two fog-trap devices along the Atacama Desert. Different climatic factors influence the efficiency of fog harvesting. In order to increase yield of collected fog water, we need to establish suitable placements that contain high rates of fog’s accumulation. As important as the location is also the building reliability of these collectors that will be installed. Their frames and skins have to be adjustable to the wind direction and resistant against strong winds and rust. Its fabric need to be more hydrophobic, elastic and with light colours to ease dripping/drainage and avoid ultra-violet deterioration. In addition, meshes should be well-tensed and frames well-embraced too. In doing so we have conceived two fog collectors: DropNet© (Höhler) and FogHive© (Suau). These designs explore climatic design parameters combined with the agile structural principles of Tensegrity and Geodesic widely developed by Bucky Fuller and Frei Otto. The research methods mainly consisted of literature review; fieldwork; comparative analysis of existing fog

  3. Fog Induced Aerosol Modification Observed by AERONET, Including Occurrences During Major Air Pollution Events

    NASA Astrophysics Data System (ADS)

    Eck, T. F.; Holben, B. N.; Reid, J. S.; Giles, D. M.; Rivas, M.; Singh, R. P.; Tripathi, S. N.; Bruegge, C. J.; Li, Z.; Platnick, S. E.; Arnold, T.; Ferrare, R. A.; Hostetler, C. A.; Burton, S. P.; Kim, J.; Kim, Y. J.; Sinyuk, A.; Dubovik, O.; Arola, A. T.; Schafer, J.; Artaxo, P.; Smirnov, A.; Chen, H.; Goloub, P.

    2015-12-01

    The modification of aerosol optical properties due to interaction with fog is examined from measurements made by sun/sky radiometers at several AERONET sites. Retrieved total column volume size distributions for cases identified as aerosol modified by fog often show very a large 'middle mode' submicron radius (~0.4 to 0.5 microns), which is typically seen as a component of a bimodal sub-micron distribution. These middle mode sized particles are often called cloud-processed or residual aerosol. This bimodal accumulation mode distribution may be due to one mode (the larger one) from fog-processed aerosol and the other from interstitial aerosol, or possibly from two different aerosol species (differing chemical composition) with differing hygroscopic growth factors. The size of the fine mode particles from AERONET retrieved for these cases exceeds the size of sub-micron sized particles retrieved for nearly all other aerosol types, suggesting significant modification of aerosols within the fog or cloud environment. In-situ measured aerosol size distributions made during other fog events are compared to the AERONET retrievals, and show close agreement in the residual mode particle size. Almucantar retrievals are analyzed from the Kanpur site in the Indo-Gangetic Plain in India (fog in January), Beijing (fog in winter), Fresno, CA in the San Joaquin Valley (fog in winter), South Korea (Yellow Sea fog in spring), Arica on the northern coast of Chile (stratocumulus), and several other sites with aerosol observations made after fog dissipated. Additionally, several major air pollution events are discussed where extremely high aerosol concentrations were measured at the surface and during which fog also occurred, resulting in the detection very large fine mode aerosols (residual mode) from AERONET retrievals in some of these events. Low wind speeds that occurred during these events were conducive to both pollutant accumulation and also fog formation. The presence of fog then

  4. Coastal fog, climate change, and the environment

    USGS Publications Warehouse

    Torregrosa, Alicia; O'Brien, Travis A.; Faloona, Ian C.

    2014-01-01

    Coastal marine fog, a characteristic feature of climates generated at the eastern boundaries of ocean basins worldwide, evokes different feelings in those who experience it (see Figure 1). Authors and poets use fog to represent mystery, bleakness, and confusion. Film directors seek out fog to shroud scenes in eerie gloominess. Tourists visiting beaches bemoan the cool and damp conditions that create a striking contrast to the sunny warm conditions typically found less than a few kilometers inland. Airline passengers delayed by fog impatiently wait for the skies to clear. Residents get used to the Sun “rising” in midday after fog dissipates.

  5. Coastal Fog, Climate Change, and the Environment

    NASA Astrophysics Data System (ADS)

    Torregrosa, Alicia; O'Brien, Travis A.; Faloona, Ian C.

    2014-12-01

    Coastal marine fog, a characteristic feature of climates generated at the eastern boundaries of ocean basins worldwide, evokes different feelings in those who experience it (see Figure 1). Authors and poets use fog to represent mystery, bleakness, and confusion. Film directors seek out fog to shroud scenes in eerie gloominess. Tourists visiting beaches bemoan the cool and damp conditions that create a striking contrast to the sunny warm conditions typically found less than a few kilometers inland. Airline passengers delayed by fog impatiently wait for the skies to clear. Residents get used to the Sun "rising" in midday after fog dissipates.

  6. Dangerous Fog Analyses and Forecast in the Maceio Airport, Brasil

    NASA Astrophysics Data System (ADS)

    Fedorova, N.; Silva, A.; Levit, V.; Santos, E.

    2010-07-01

    A small airplane fatal accident has occurred near Maceio Airport, on the coastal region on 26 July 2007. Low visibility in the intensive fog has provoked this accident. Weather forecast analysis, published in the local and central Brazilian newspapers during 2007, showed fog forecast absence during whole year. A study of the fog formation causes was elaborated using the high and low resolution satellite data, radar data, different products of NCEP reanalysis data and high resolution regional MM5 model simulation. The trade winds with a weak cyclonic curvature at the low levels have generated the humidity convergence at the superficial layers up to 850hPa on the coastal region. An anticyclonic circulation existence at the middle and higher levels and weak ascendant motion (by NCEP data) have support a weak convection development. The low levels clouds development on the continental region and convection development over ocean were confirmed by the radar and satellite data. A thermal inversion near surface level (up to 150m) and descendent movement at the middle and high levels were identified by MM5 model. Fog formation was simulated by PAFOG model. The conventional airport observations have shown the minimal visibility of 200m between 4 and 7a.m. Moreover visibility less than 1000m between 1 and 8a.m. with the minimal visibility of 213m was simulated by PAFOG model.

  7. Signal processing for fiber optic gyroscope (FOG)

    NASA Astrophysics Data System (ADS)

    Tanaka, Ryuichi; Kurokawa, Akihiro; Sato, Yoshiyuki; Magome, Tsutomu; Hayakawa, Yoshiaki; Nakatani, Ichiro; Kawaguchi, Junichiro

    1994-11-01

    A fiber-optic gyroscope (FOG) is expected to be the next generation gyroscope for guidance and control, because of various advantages. We have been developing the FOG-Inertial Navigation and Guidance (ING) for M-V satellite launching rocket of the Institute of Space and Astronautical Science (ISAS) since 1990. The FOG-ING consists of an Inertial Measurement Unit (IMU) and an Central Processing Unit Assembly. At current status, the proto-flight model FOG-IMU is being actively developed. And the flight test of the FOG-ING was performed on February 20, 1993, aboard M-3SII-7 satellite launching rocket at the ISAS test facilities in Uchinoura, Japan. This paper presents the signal processing technologies of our FOG which are used for the above FOG-ING.

  8. Climatology of fog in SW-Iceland

    NASA Astrophysics Data System (ADS)

    Barranco, Aurelio; Ólafsson, Haraldur

    2016-04-01

    The climatology of fog in Keflavik Airport in Southwest-Iceland has been investigated for the latter half of the 20th Century. Fog is twice as frequent in the late night than in the afternoon, suggesting important, but not dominating, impact of the diurnal cycle. There is large interannual variability in the frequency of fog, but no clear long-term trend. However, there is a clear shift in seasonal frequency; the period 1953-1977 had relatively frequent fog in the autumn, while 1978-1998, fog is relatively frequent in the spring and summer. This indicates sensitivity of the fog to mean sea surface temperatures. An attempt is made to assess frequency of fog in climate scenarii.

  9. Influence of aqueous chemistry on the chemical composition of fog water and interstitial aerosol in Fresno

    NASA Astrophysics Data System (ADS)

    Kim, Hwajin; Ge, Xinlei; Collier, Sonya; Xu, Jianzhong; Sun, Yele; Wang, Youliang; Herckes, Pierre; Zhang, Qi

    2015-04-01

    A measurement study was conducted in the Central Valley (Fresno) of California in January 2010, during which radiation fog events were frequently observed. Fog plays important roles in atmospheric chemistry by scavenging aerosol particles and trace gases and serving as a medium for various aqueous-phase reactions. Understanding the effects of fog on the microphysical and chemical processing of aerosol particles requires detailed information on their chemical composition. In this study, we characterized the chemical composition of fog water and interstitial aerosol particles to study the effects of fog processing on aerosol properties. Fog water samples were collected during the 2010 Fresno campaigns with a Caltech Active Strand Cloud water Collector (CASCC) while interstitial submicron aerosols were characterized in real time with an Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and a scanning Mobility Particle Sizer (SMPS). The fog water samples were later analyzed using the HR-ToF-AMS, ion chromatography, and a total carbon analyzer. The chemical composition and characteristics of interstitial particles during the fog events were compared to those of dissolved inorganic and organic matter in fog waters. Compared to interstitial aerosols, fog water is composed of a higher fraction of ammonium nitrate and oxygenated organics, due to aqueous formation of secondary aerosol species as well as enhanced gas-to-particle partitioning of water soluble species under water rich conditions. Sulfate is formed most efficiently in fog water although its contribution to total dissolved mass is relatively low. The HR-ToF-AMS mass spectra of organic matter in fog water (FOM) are very similar to that of oxygenated organic aerosols (OOA) derived from positive matrix factorization (PMF) of the HR-ToF-AMS spectra of ambient aerosol (r2 = 0.96), but FOM appears to contain a large fraction of acidic functional groups than OOA. FOM is also enriched of

  10. Influence of fog parameters on withstand voltage of contaminated insulators

    SciTech Connect

    Naito, K.; Ito, M.; Katsukawa, H.; Kawaguchi, T.; Suzuki, Y.

    1983-03-01

    This paper describes the investigation results of fog parameters which affect the withstand voltage of contaminated insulators. As a result, the guideline is proposed on fog conditions such as density, droplet size distribution, temperature rise in the fog room, and so on, basing upon the comparison between natural and artificial fog conditions and the relation between fog condition and power-frequency withstand voltage.

  11. A Study of Aerosols Transportation around City Boundary in the Fog Weather

    NASA Astrophysics Data System (ADS)

    Ding, J.; Li, J. H.; Liu, Y.; Zhang, B. L.; Wang, Q. T.

    2011-09-01

    The structure of city surface seriously affects transport and diffusion of pollutant aerosol particles in the fog weather. So dynamic model population balance model (PBM) of aerosol particles and multiphase-coupled flow model were established to describe the fluid-particle system of fog. Based on the Eulerian-Lagrangian method and Multi-Monte Carlo method, a study of aerosols transportation around city boundary was conducted. The computed results show a part of aerosols change into droplets during the formation of fog, and the average sizes of aerosols, droplets are about 0.032 7 μm and 28.7 μm with time evolution to 60 min. For the development of fog, with time of 60 min and wind of 2 m/s, the number of aerosol is down to 84.5% of initial value, and the average particle size is down to 22.1 μm accordingly. During the dissipation of fog, the numbers of aerosol and fog droplet are decreased to the 1.65% and 0.016 5% of initial value. As wind speed rising, the turbulent motion strength of particles is increased. Eventually, the droplets have almost disappeared, and a small number of aerosols are still suspended in the atmosphere. The computed results reflect the transport and dynamic characteristics for respirable aerosols around city boundary during three stages of fog.

  12. Radiative characteristics of fog over the Indo-Gangetic Plains during northern winter

    NASA Astrophysics Data System (ADS)

    Sathiyamoorthy, V.; Arya, R.; Kishtawal, C. M.

    2016-09-01

    The Indo-Gangetic plains (IGP), spread across northern parts of India, Pakistan and Bangladesh is a hot-spot for fog formation during northern winter. The unavailability of long-term fog data over the IGP from any space based platform incites the utilization of monthly International Satellite Cloud Climatology Project (ISCCP-D2) cloud data for studying fog at this region. Fog is primarily represented as low level stratus and stratocumulus clouds in ISCCP cloud data. Top of atmosphere cloud radiative forcing measured by Clouds and the Earth's Radiant Energy System instruments onboard Aqua/Terra satellites indicates a net radiative cooling by fog over the IGP region. Also, the analysis of gridded surface temperature data from India meteorological department suggests that negative temperature anomalies prevail over the regions of radiative cooling exerted by fog. These negative anomalies in surface temperature may cause further dipping of the temperature over the IGP during fog years. This study suggests that foggy winter will be colder than non-foggy winter over the IGP.

  13. Fog Collection on Polyethylene Terephthalate (PET) Fibers: Influence of Cross Section and Surface Structure.

    PubMed

    Azad, M A K; Krause, Tobias; Danter, Leon; Baars, Albert; Koch, Kerstin; Barthlott, Wilhelm

    2017-03-22

    Fog-collecting meshes show a great potential in ensuring the availability of a supply of sustainable freshwater in certain arid regions. In most cases, the meshes are made of hydrophilic smooth fibers. Based on the study of plant surfaces, we analyzed the fog collection using various polyethylene terephthalate (PET) fibers with different cross sections and surface structures with the aim of developing optimized biomimetic fog collectors. Water droplet movement and the onset of dripping from fiber samples were compared. Fibers with round, oval, and rectangular cross sections with round edges showed higher fog-collection performance than those with other cross sections. However, other parameters, for example, width, surface structure, wettability, and so forth, also influenced the performance. The directional delivery of the collected fog droplets by wavy/v-shaped microgrooves on the surface of the fibers enhances the formation of a water film and their fog collection. A numerical simulation of the water droplet spreading behavior strongly supports these findings. Therefore, our study suggests the use of fibers with a round cross section, a microgrooved surface, and an optimized width for an efficient fog collection.

  14. Fog Prediction for Road Traffic Safety in a Coastal Desert Region

    NASA Astrophysics Data System (ADS)

    Bartok, Juraj; Bott, Andreas; Gera, Martin

    2012-12-01

    Modern weather prediction models use relatively high grid resolutions as well as sophisticated parametrization schemes for microphysical and other subgrid-scale atmospheric processes. Nonetheless, with these models it remains a difficult task to perform successful numerical fog forecasts since many factors controlling a particular fog event are not yet sufficiently simulated. Here we describe our efforts to create a mechanism that produces successful predictions of fog in the territory located on the north coast of the Arabian Peninsula. Our approach consists in the coupling of the one-dimensional PAFOG fog model with the three-dimensional WRF 3.0 (Weather Research and Forecast) modelling system. The proposed method allows us to construct an efficient operative road traffic warning system for the occurrence of fog in the investigated region. In total 84 historical situations were studied during the period 2008-2009. Moreover, results of operative day-by-day fog forecasting during January and February 2010 are presented. For the investigated arid and hot climate region the land-sea breeze circulation seems to be the major factor affecting the diurnal variations of the meteorological conditions, frequently resulting in the formation of fog.

  15. A Study of Fog Characteristics Using a Coupled WRF-COBEL Model Over Thessaloniki Airport, Greece

    NASA Astrophysics Data System (ADS)

    Stolaki, Stavroula; Pytharoulis, Ioannis; Karacostas, Theodore

    2012-05-01

    An attempt is made to couple the one dimensional COBEL-ISBA (Code de Brouillard à l'Échelle Locale-Interactions Soil Biosphere Atmosphere) model with the WRF (Weather Research and Forecasting)-ARW (Advanced Research WRF) numerical weather prediction model to study a fog event that formed on 20 January 2008 over Thessaloniki Airport, Greece. It is the first time that the coupling of COBEL and WRF models is achieved and applied to a fog event over an airport. At first, the performance of the integrated WRF-COBEL system is investigated, by validating it against the available surface observations. The temperature and humidity vertical profiles were used for initializing the model. The performance of WRF-COBEL is considered successful, since it realistically simulated the fog onset and dissipation better than the WRF alone. The COBEL's sensitivity to initial conditions such as temperature and specific humidity perturbations was also tested. It is found that a small increase of temperature (~1°C) counteracts fog development and results in less fog density. On the other hand, a small decrease of temperature results in much denser fog formation. It is concluded that the integrated model approach for aviation applications can be useful to study fog impact on local traffic and aviation.

  16. Impact of Fog on Electromagnetic Wave Propagation

    NASA Astrophysics Data System (ADS)

    Morris, Jonathon; Fleisch, Daniel

    2002-04-01

    This experiment was designed to explore the impact of fog on electromagnetic radiation, in particular microwaves and infrared light. For years law enforcement agencies have used microwave radiation (radar guns) to measure the speed of vehicles, and the last ten years has seen increased use of LIDAR, which uses 905-nm infrared radiation rather than microwaves. To evaulate the effect of fog on the operation of these devices, we have constructed a fog chamber with microwave and optical portals to allow light from a HeNe laser and 10.6-GHz microwaves to propagate through various densities of fog. Data is acquired using Vernier Logger Pro and analyzed using MATLAB and Mathematica. Using the attenuation of the laser light to determine fog density, the impact of fog on the signal-to-noise ratio of both microwave and IR devices may be quantified, and the maximum useful range may be calculated.

  17. Fog spontaneously folds mosquito wings

    NASA Astrophysics Data System (ADS)

    Dickerson, Andrew K.; Liu, Xing; Zhu, Ting; Hu, David L.

    2015-02-01

    The flexibility of insect wings confers aerodynamic benefits, but can also present a hazard if exposed to fog or dew. Fog can cause water to accumulate on wings, bending them into tight taco shapes and rendering them useless for flight. In this combined experimental and theoretical study, we use high-speed video to film the spontaneous folding of isolated mosquito wings due to the evaporation of a water drop. We predict shapes of the deformed wing using two-dimensional elastica theory, considering both surface tension and Laplace pressure. We also recommend fold-resistant geometries for the wings of flapping micro-aerial vehicles. Our work reveals the mechanism of insect wing folding and provides a framework for further study of capillarity-driven folding in both natural and biomimetic systems at small scales.

  18. The cold-fog test

    SciTech Connect

    Chisholm, W.A.; Ringler, K.G.; Erven, C.C.

    1996-10-01

    The electrical performance of outdoor insulation degrades severely during combinations of factors that include surface contamination (C), ice (I), fog (F) and an ambient temperature that rises through 0 C (T{sub 0{degree}}). Failures at operating voltage on 115-kV, 230-kV and 500-kV systems occur with increasing probability under these conditions. A new CFT{sub 0{degree}} or cold-fog test method has been developed to reproduce the flashovers at all three voltage levels. Three options are identified for improving CFT{sub 0{degree}} performance: use of semi-conductive glazes, substitution of silicone for porcelain and use of silicone coatings on existing porcelain insulators.

  19. Measurements of dew and fog chemical composition at a rural site

    NASA Astrophysics Data System (ADS)

    Straub, D.; Sokoloff, R.; Ressler, D.; Herckes, P.

    2012-12-01

    Liquid water in the atmosphere has been shown to play an important role in the transport, transformation, and removal of aerosol particles and soluble gases. Dew and fog represent two forms of the atmospheric aqueous phase, both of which may enhance the deposition of trace species and enable fast aqueous phase reactions. Compared to precipitation, dews and fogs have longer residence times at ground level and therefore may be strongly influenced by local sources. Fog composition measurements in the United States have been limited to relatively few locations along the East and West coasts while only a handful of studies have focused on dew composition. To extend our knowledge of dew and fog composition, measurements have been made on the campus of Susquehanna University in central Pennsylvania. Fog samples have been collected since 2007 using an automated Caltech Heated Rod Cloudwater Collector (CHRCC). Dew sampling began during the summer of 2012 using a 90 cm by 90 cm Teflon sheet mounted on a polystyrene foam panel. All samples were analyzed for pH and one of more of the following: major inorganic ions, organic acids, total organic carbon (TOC), and trace metals. Dew and fog concentrations varied widely between samples, though concentrations of most species in fog generally exceeded those in dew. The median pH was approximately 6.0 for fog and 7.0 for dew, both of which are much higher than the median value of 4.6 for precipitation in this region. Ammonium was the most abundant ionic species in the fog samples, followed by sulfate, calcium, and nitrate. Dew samples were also dominated by ammonium, though calcium was significant in some samples. Sulfate and nitrate concentrations were substantially lower in the dew samples. Formate and acetate were the most abundant organic acids in both types of samples, although those species made up much larger fraction of the total solute in the dew samples. In addition, oxalate and propionate were observed in both types of

  20. Impact of fog-drip versus fog immersion on leaf-level function of Bishop pines

    NASA Astrophysics Data System (ADS)

    Baguskas, S. A.; Still, C. J.

    2013-12-01

    Fog-water is known to be an important water source to plants in coastal, Mediterranean climates because it augments plant available water several months after the last winter rain, when conditions are otherwise warm and dry. While fog-drip to the soil surface is the most obvious contribution of fog to the water budget of an ecosystem, recent studies provide convincing evidence that foliar absorption of fog water is also possible. The focus of our research was to assess the relative importance of fog-drip and fog immersion on the photosynthetic capacity and gas exchange rates of a coastal pine species, Bishop pine (Pinus muricata, D.Don), a drought sensitive species restricted to the fogbelt of coastal California and offshore islands. We conducted a greenhouse study where we manipulated fog water inputs to potted Bishop pine saplings during a three-week dry-down period. Fifteen saplings were randomly assigned one of three treatments: 1) fog-drip and fog-immersion, 2) fog immersion alone, and 3) no fog water inputs. We artificially generated nighttime fog events using an ultrasonic device, which produces fog droplets. Given that the canopy architecture varied between saplings, we standardized the amount of fog-drip plants received by preventing direct fog drip from the canopy, and instead added the average amount of fog water that would have fallen from each canopy. To detect changes in soil moisture, we installed volumetric soil moisture probes in each pot at 2 and 10 cm depth. The plant response variables measured were photosynthetic capacity and maximum gas exchange rates of sapling trees. Our results show that plants which received both fog-drip and fog immersion sustained higher gas exchange rates and photosynthetic capacity through the dry-down period compared to trees in other treatment groups. Trees that received only fog immersion had lower rates of gas exchange and lower photosynthetic capacity relative to trees that received both fog-drip and fog immersion

  1. Analysis of the microphysical structure of heavy fog using a droplet spectrometer: A case study

    SciTech Connect

    Niu, S.; Liu, Y.; Lu, C.; Zhao, L.; Lv, J.; Yang, J.

    2010-01-01

    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{sup o}N, 118.7{sup o}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{sup -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.

  2. FOG-1 and GATA-1 act sequentially to specify definitive megakaryocytic and erythroid progenitors

    PubMed Central

    Mancini, Elena; Sanjuan-Pla, Alejandra; Luciani, Luisa; Moore, Susan; Grover, Amit; Zay, Agnes; Rasmussen, Kasper D; Luc, Sidinh; Bilbao, Daniel; O'Carroll, Donal; Jacobsen, Sten Eirik; Nerlov, Claus

    2012-01-01

    The transcription factors that control lineage specification of haematopoietic stem cells (HSCs) have been well described for the myeloid and lymphoid lineages, whereas transcriptional control of erythroid (E) and megakaryocytic (Mk) fate is less understood. We here use conditional removal of the GATA-1 and FOG-1 transcription factors to identify FOG-1 as required for the formation of all committed Mk- and E-lineage progenitors, whereas GATA-1 was observed to be specifically required for E-lineage commitment. FOG-1-deficient HSCs and preMegEs, the latter normally bipotent for the Mk and E lineages, underwent myeloid transcriptional reprogramming, and formed myeloid, but not erythroid and megakaryocytic cells in vitro. These results identify FOG-1 and GATA-1 as required for formation of bipotent Mk/E progenitors and their E-lineage commitment, respectively, and show that FOG-1 mediates transcriptional Mk/E programming of HSCs as well as their subsequent Mk/E-lineage commitment. Finally, C/EBPs and FOG-1 exhibited transcriptional cross-regulation in early myelo-erythroid progenitors making their functional antagonism a potential mechanism for separation of the myeloid and Mk/E lineages. PMID:22068055

  3. FOG-1 and GATA-1 act sequentially to specify definitive megakaryocytic and erythroid progenitors.

    PubMed

    Mancini, Elena; Sanjuan-Pla, Alejandra; Luciani, Luisa; Moore, Susan; Grover, Amit; Zay, Agnes; Rasmussen, Kasper D; Luc, Sidinh; Bilbao, Daniel; O'Carroll, Donal; Jacobsen, Sten Eirik; Nerlov, Claus

    2012-01-18

    The transcription factors that control lineage specification of haematopoietic stem cells (HSCs) have been well described for the myeloid and lymphoid lineages, whereas transcriptional control of erythroid (E) and megakaryocytic (Mk) fate is less understood. We here use conditional removal of the GATA-1 and FOG-1 transcription factors to identify FOG-1 as required for the formation of all committed Mk- and E-lineage progenitors, whereas GATA-1 was observed to be specifically required for E-lineage commitment. FOG-1-deficient HSCs and preMegEs, the latter normally bipotent for the Mk and E lineages, underwent myeloid transcriptional reprogramming, and formed myeloid, but not erythroid and megakaryocytic cells in vitro. These results identify FOG-1 and GATA-1 as required for formation of bipotent Mk/E progenitors and their E-lineage commitment, respectively, and show that FOG-1 mediates transcriptional Mk/E programming of HSCs as well as their subsequent Mk/E-lineage commitment. Finally, C/EBPs and FOG-1 exhibited transcriptional cross-regulation in early myelo-erythroid progenitors making their functional antagonism a potential mechanism for separation of the myeloid and Mk/E lineages.

  4. Efficient Fractionation and Analysis of Fatty Acids and their Salts in Fat, Oil and Grease (FOG) Deposits.

    PubMed

    Benecke, Herman P; Allen, Sara K; Garbark, Daniel B

    2017-02-01

    A fractionation methodology of fat, oil and grease (FOG) deposits was developed based on the insolubility of fatty acid salts in dichloromethane (DCM) and the relatively high solubility of fatty acids and triglycerides in DCM. Using this method, coupled with spectral analysis, it was shown that fatty acids rather than fatty acid salts were the predominant species in FOG deposits obtained from three metropolitan locations in the United States and that fatty acid triglycerides were either not detected or were present in very small concentrations. This solubility-based fractionation approach also revealed the presence of nitrogen-containing compounds that had not been previously detected in FOG deposits including peptides and (or) proteins. The comparison of the ratios of stearic acid salts to stearic acid versus the ratio of palmitic acid salts to palmitic acid in FOG deposits may indicate that the initial step in FOG deposit formation is the preferential precipitation of stearic acid salts.

  5. Inexpensive anti-fog coating for windows

    NASA Technical Reports Server (NTRS)

    Carmin, D. L., Jr.; Morrison, H. D.

    1971-01-01

    Coating applications include anti-fog protection for deep-sea diving equipment, fire protection helmets, and windows of vehicles used in hazardous environments. Basic coating composition includes liquid detergent, deionized water, and oxygen compatible fire-resistant oil. Composition prevents visor fogging under maximum metabolic load for 5 hours and longer.

  6. On the fog variability over south Asia

    NASA Astrophysics Data System (ADS)

    Syed, F. S.; Körnich, H.; Tjernström, M.

    2012-04-01

    An increasing trend in fog frequencies over south Asia during winter in the last few decades has resulted in large economical losses and has caused substantial difficulties in the daily lives of people. In order to better understand the fog phenomenon, we investigated the climatology, inter-annual variability and trends in the fog occurrence from 1976 to 2010 using observational data from 82 stations, well distributed over India and Pakistan. Fog blankets large area from Pakistan to Bangladesh across north India from west to east running almost parallel to south of the Himalayas. An EOF analysis revealed that the fog variability over the whole region is coupled and must therefore be governed by some large scale phenomenon on the inter-annual time scale. Significant trends were found in the fog frequencies and this increase is not gradual, as seen in the humidity, but shows two distinct regimes shifts in 1990 and 1998 with respect to both mean and variance. The fog is also detected in ERA-Interim 3 hourly, surface and model level forecast data when using the concept of "cross-over temperature" combined with boundary layer stability. This detected fog index is able to reproduce the regime shift around 1998 and shows that the method can be applied to detect fog over south Asia. The inter-annual variability seems to be associated with the wave train originating from north Atlantic in the upper atmosphere that causes higher pressure over the region,resulting in increased boundary layer stability and surface-near relative humidity. The trend and shifts in the fog occurrence seems to be associated with the gradual increasing trend in relative humidity from 1990 onwards.

  7. On the fog variability over south Asia

    NASA Astrophysics Data System (ADS)

    Syed, F. S.; Körnich, H.; Tjernström, M.

    2012-12-01

    An increasing trend in fog frequencies over south Asia during winter in the last few decades has resulted in large economical losses and has caused substantial difficulties in the daily lives of people. In order to better understand the fog phenomenon, we investigated the climatology, inter-annual variability and trends in the fog occurrence from 1976 to 2010 using observational data from 82 stations, well distributed over India and Pakistan. Fog blankets large area from Pakistan to Bangladesh across north India from west to east running almost parallel to south of the Himalayas. An EOF analysis revealed that the fog variability over the whole region is coupled and therefore must be governed by some large scale phenomenon on the inter-annual time scale. Significant positive trends were found in the fog frequency but this increase is not gradual, as with the humidity, but comprises of two distinct regimes shifts, in 1990 and 1998, with respect to both mean and variance. The fog is also detected in ERA-Interim 3 hourly, surface and model level forecast data when using the concept of "cross-over temperature" combined with boundary layer stability. This fog index is able to reproduce the regime shift around 1998 and shows that the method can be applied to analyze fog over south Asia. The inter-annual variability seems to be associated with the wave train originating from the North Atlantic in the upper troposphere that when causing higher pressure over the region results in an increased boundary layer stability and surface-near relative humidity. The trend and shifts in the fog occurrence seems to be associated with the gradual increasing trend in relative humidity from 1990 onwards.

  8. High-resolution two dimensional advective transport

    USGS Publications Warehouse

    Smith, P.E.; Larock, B.E.

    1989-01-01

    The paper describes a two-dimensional high-resolution scheme for advective transport that is based on a Eulerian-Lagrangian method with a flux limiter. The scheme is applied to the problem of pure-advection of a rotated Gaussian hill and shown to preserve the monotonicity property of the governing conservation law.

  9. Evolution and advection of solar mesogranulation

    NASA Technical Reports Server (NTRS)

    Muller, Richard; Auffret, Herve; Roudier, Thierry; Vigneau, Jean; Simon, George W.; Frank, Zoe; Shine, Richard A.; Title, Alan M.

    1992-01-01

    A three-hour sequence of observations at the Pic du Midi observatory has been obtained which shows the evolution of solar mesogranules from appearance to disappearance with unprecedented clarity. It is seen that the supergranules, which are known to advect the granules with their convective motion, also advect the mesogranules to their boundaries. This process controls the evolution and disappearance of mesogranules.

  10. Satellite based classification (haze, fog) and affected area estimation over Indo - Pak Sub-Continent

    NASA Astrophysics Data System (ADS)

    Ghauri, Badar; Zafar, Sumaira

    2016-07-01

    Northern Pakistan and bordering Indian Punjab experience intense smog and fog during fall and winters. Environmentalists have been raising their voices over the situation and demanded control over regional emissions to save the livelihood of millions of dwellers whose trade, commerce and agriculture is at stake because of long smog/ fog spells.. This paper estimates the area affected by haze, smog and fog during 2006- 2010. MODIS (geo-referenced MODIS subsets India1, 2 &3) of the area in Pakistan and India from 2006 to 2010 for the period October to February) were analyzed using state of the art software ENVI 4.2 and ArcGIS 10.2. This process resulted in area belonging to each class that is; haze, smog and fog. On the basis of density, haze and fog cover was determined. Variations in fog cover, its density and identification of location of fog initiation process were also determined using near real time (30 minutes) METEOSAT-7 IODC data where actually fog formation started and then extended to the area of favorable conditions. Haze has been noticed to intensify due to massive burning of agricultural waste (rice husk) in India and Pakistan towards the end of October each year. MODIS thermal anomalies/fire data (MYD 14) were also used to verify this activity on the ground, which results in hazy conditions at regional level during fall months. Haze-affected area during 2006 to 2010 in Pakistan ranged from 155,000 Km2 to 354,000 Km2 and in India it ranged from 333,000 Km2 to 846,000 Km2. Similarly winter fog cover during this period in Pakistan varied from 136,000 Km2 to 381,000 Km2 and in India it was estimated at 327,000 Km2 to 566,000 Km2. This phenomenon was more prominent in India than in Pakistan where and fog cover was at least twice than that was observed in Pakistan. It has been noted that area covered by fog, smog and haze doubled during the study period in the region. Atmospheric dimming during autumn/ fall also reduces the mixing height leading to greater

  11. Streamflow, Fog, and Fog-Drip in the California Coast Range

    NASA Astrophysics Data System (ADS)

    Sawaske, S. R.; Freyberg, D. L.

    2013-12-01

    The onshore movement of marine fog from coastal waters is a common occurrence during summer months along much of the contiguous U.S. Pacific Coast. Because the fog-season tends to occur during the precipitation-free dry-season, any additional input of moisture or reduction in loss of moisture through evapotranspiration provided by marine layer can be an important factor in localized hydrologic systems. In an effort to quantify some of the effects of fog on the regional dry-season hydrology, a study site within the Santa Cruz Mountains of central California was established. The fog-laden coastside and predominately fog-free San Francisco Bay-side of the study area provided an excellent opportunity to assess the impacts of the presence and absence of fog on ecohydrological processes. Streamflow, fog-drip, soil moisture, and weather conditions were measured from May-September. Bayside streams were found to be almost all intermittent, with much higher rates of baseflow recession compared to the predominately perennial coastside streams. Fog-drip was essentially nonexistent on the bayside, while highly variable amounts were recorded on the coastside. Maximum rates and seasonal totals of drip were found within stands of mature conifers (Sequoia sempervirens and Pseudotsuga menziesii) along exposed, often windy ridgelines. Rates of up to 19 in (48 cm)/month of fog-drip were recorded. Consequently, frequent infiltration events to depths of at least 9 in (23 cm) were also documented. Over the course of the study soil moisture levels at high fog-drip locations either increased, or were roughly equivalent to initial spring conditions from the onset of data collection. Increases of flow in coastside streams, under otherwise receding conditions, were found to coincide with fog and fog-drip events. These results indicate that the presence of fog can significantly affect dry-season hydrologic conditions of some coastal locations.

  12. Arctic Coastal Fog over Greenland Glaciers using an Improved MODIS Fog Detection Method and Ground Observations

    NASA Astrophysics Data System (ADS)

    Jiskoot, H.; Harvey, T.; Gilson, G.

    2015-12-01

    Annual breakup of sea ice causes fog in Arctic coastal regions, which can both reduce and enhance glacier melt. With progressive sea ice loss and increasing temperatures and atmospheric moisture in the Arctic, it is essential to determine the frequency and spatial extent of fog in order to understand its present and future effects on glacier mass balance. Previously, we determined Greenland coastal fog to peak with 15-25% of days in July. Here, we present the spatial and vertical extent of significant melt-season fog events over Greenland coastal glaciers and the ice sheet. To this end, we modified a MODIS fog/low stratus detection method by Bendix et al. (2005), with verification by weather and radiosonde data, timelapse and Landsat imagery, and independent fog classifications. Our fog-detection method uses MODIS Levels 1b and 2, processed in an ENVI-ArcGIS environment as follows: 1) visual examination and application of vegetation and snow indices; 2) initial fog/low stratus discrimination with novel band thresholds and cloud products; 3) verification using cloud phase/temperature products; 4) cleaning misclassified pixels; 5) calculating fog/low stratus optical and geometrical thickness; 6) final differentiation of fog from low stratus using edge-pixel detection, trend-surface fitting, and DEM filling. The end product consists of 500 m fog-mask pixel maps over Greenland, with minimum and maximum possible extents based on classification of fog versus low stratus. Our results show that fog can cover extensive areas of the Greenland ice masses. Persistent fog events in early, mid, and late melt-season were extracted for East Greenland using fog rim detection overlain on the GIMP DEM, the Randolph Glacier Inventory, and a coast shapefile. E.g., a 4 July 2002 fog event covers 4300-5000 km2 of ice, with a maximum inland extent of 85 km to an elevation of 1250 m asl. Fog thickness over ice is 20-800 m, but can be underestimated by >50 m compared to radiosonde data.

  13. Fog droplet distribution functions for lidar.

    PubMed

    Mallow, J V

    1982-04-15

    The interpretation of lidar data on fog has been limited by two obstacles: approximations in the form of the Mie scattering cross sections for water droplets, and droplet size distribution functions whose relationship to the experiment has not been clear. This paper develops a method for generating distribution functions from experimental data. These functions are then used with newly available Mie cross sections to obtain backscattering and extinction coefficients for singly scattered ruby laser pulses in fog. The results show what experimental lidar accuracies are needed to uniquely determine fog droplet size distribution.

  14. Fog droplet distribution functions for lidar

    SciTech Connect

    Mallow, J.V.

    1982-04-15

    The interpretation of lidar data on fog has been limited by two obstacles: approximations in the form of the Mie scattering cross sections for water droplets, and droplet size distribution functions whose relationship to the experiment has not been clear. This paper develops a method for generating distribution functions from experimental data. These functions are then used with newly available Mie cross sections to obtain backscattering and extinction coefficients for singly scattered ruby laser pulses in fog. The results show what experimental lidar accuracies are needed to uniquely determine fog droplet size distribution.

  15. Persistence of cluster synchronization under the influence of advection.

    PubMed

    Guirey, Emma; Bees, Martin; Martin, Adrian; Srokosz, Meric

    2010-05-01

    We present a study on the emergence of spatial structure in plankton dynamics under the influence of stirring and mixing. A distribution of plankton is represented as a lattice of nonidentical, interacting, oscillatory plankton populations. Each population evolves according to (i) the internal biological dynamics represented by an NPZ model with population-specific phytoplankton growth rate, (ii) sub-grid-cell stirring and mixing parameterized by a nearest-neighbor coupling, and (iii) explicit advection resulting from a constant horizontal shear. Using the methods of synchronization theory, the emergent spatial structure of the simulation is investigated as a function of the coupling strength and rate of advection. Previous work using similar methods has neglected the effects of explicit stirring (i.e., at scales larger than the grid cell), leaving as an open question the relevance of the work to real marine systems. Here, we show that persistent spatial structure emerges for a range of coupling strengths for all realistic levels of surface ocean shear. Spatially, this corresponds to the formation of temporally evolving clusters of local synchronization. Increasing shear alters the spatial characteristics of this clustering by stretching and narrowing patches of synchronized dynamics. These patches are not stretched into stripes of synchronized abundance aligned with the flow, as may be expected, but instead lie at an angle to the flow. This study shows that advection does not diminish the relevance of conclusions from previous studies of spatial structure in plankton simulations. In fact, the inclusion of advection adds characteristic filamental structure, as observed in real-world plankton distributions. The results also show that the ability of coupled oscillators to synchronize depends strongly on the spatial arrangement of oscillator natural frequencies; under the influence of advection, therefore, the impact of the coupling strength on the emergent spatial

  16. Climatic characteristics and regionalization of fogs in China

    NASA Astrophysics Data System (ADS)

    Hao, T. Y.; Chen, S. C.; Han, S. Q.; Shan, X. L.; Meng, L. H.

    2017-01-01

    Using trend coefficient method, vector analysis method, and monitored meteorological data across China, climatic characteristics and spatial pattern of fogs in China were investigated. The results show that most fogs occur in southeastern China. Thin fogs usually occur in fog-rare regions and dense fogs take place in fog-prone regions. The number of annual fog days in most regions of China exhibits a decreasing trend from 1980 to 2010. It also found that the regions with more fog days correspond to the lower concentration degree of fogs, and vice versa. In terms of the national scale, the concentration periods of fogs are mainly in November, December, and January in China. We further classified the occurrence frequencies of fogs into five spatial distribution patterns over a single year according to the spatial distribution characteristics of fogs occurrence frequencies of 36 dekads, namely, a whole year can be correspondingly divided into five phases. Based on this, multi-year average fog-prone regions in the five phases are obtained. Our results also identify the high incidence periods of fogs in different fog-prone regions.

  17. Friend of GATA (FOG) interacts with the nucleosome remodeling and deacetylase complex (NuRD) to support primitive erythropoiesis in Xenopus laevis.

    PubMed

    Mimoto, Mizuho S; Christian, Jan L

    2012-01-01

    Friend of GATA (FOG) plays many diverse roles in adult and embryonic hematopoiesis, however the mechanisms by which it functions and the roles of potential interaction partners are not completely understood. Previous work has shown that overexpression of FOG in Xenopus laevis causes loss of blood suggesting that in contrast to its role in mammals, FOG might normally function to repress erythropoiesis in this species. Using loss-of-function analysis, we demonstrate that FOG is essential to support primitive red blood cell (RBC) development in Xenopus. Moreover, we show that it is specifically required to prevent excess apoptosis of circulating primitive RBCs and that in the absence of FOG, the pro-apoptotic gene Bim-1 is strongly upregulated. To identify domains of FOG that are essential for blood development and, conversely, to begin to understand the mechanism by which overexpressed FOG represses primitive erythropoiesis, we asked whether FOG mutants that are unable to interact with known co-factors retain their ability to rescue blood formation in FOG morphants and whether they repress erythropoiesis when overexpressed in wild type embryos. We find that interaction of FOG with the Nucleosome Remodeling and Deacetylase complex (NuRD), but not with C-terminal Binding Protein, is essential for normal primitive RBC development. In contrast, overexpression of all mutant and wild type constructs causes a comparable repression of primitive erythropoiesis. Together, our data suggest that a requirement for FOG and its interaction with NuRD during primitive erythropoiesis are conserved in Xenopus and that loss of blood upon FOG overexpression is due to a dominant-interfering effect.

  18. Adaption of the Air Weather Service Fog Model to Forecast Radiation Fog Events in the Southeast United States

    DTIC Science & Technology

    1997-03-01

    ADAPTATION OF THE AIR WEATHER SERVICE FO MODEL TO FORECAST RADIATION FOG EVENT IN THE SOUTHEAST UNITED STATES THESIS Andrew C. Goodnite, Captain...ENP/97M-06 ADAPTATION OF THE AIR WEATHER SERVICE FOG MODEL TO FORECAST RADIATION FOG EVENTS IN THE SOUTHEAST UNITED STATES THESIS Andrew C. Goodnite...AIR WEATHER SERVICE FOG MODEL TO FORECAST RADIATION FOG EVENTS IN THE SOUTHEAST UNITED STATES THESIS Presented to the Faculty of the Graduate School of

  19. 33 CFR 118.130 - Fog signals.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... to fog or other causes, the District Commander may require or authorize the installation of one or... the installation, range, and sound frequencies provisions in Subpart 67.10 of Part 67 of this...

  20. 33 CFR 118.130 - Fog signals.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... to fog or other causes, the District Commander may require or authorize the installation of one or... the installation, range, and sound frequencies provisions in Subpart 67.10 of Part 67 of this...

  1. 33 CFR 118.130 - Fog signals.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... to fog or other causes, the District Commander may require or authorize the installation of one or... the installation, range, and sound frequencies provisions in Subpart 67.10 of Part 67 of this...

  2. Fog interception by Ball moss (Tillandsia recurvata)

    NASA Astrophysics Data System (ADS)

    Guevara-Escobar, A.; Cervantes-Jiménez, M.; Suzán-Azpiri, H.; González-Sosa, E.; Hernández-Sandoval, L.; Malda-Barrera, G.; Martínez-Díaz, M.

    2011-08-01

    Interception losses are a major influence in the water yield of vegetated areas. For most storms, rain interception results in less water reaching the ground. However, fog interception can increase the overall water storage capacity of the vegetation and once the storage is exceeded, fog drip is a common hydrological input. Fog interception is disregarded in water budgets of semiarid regions, but for some plant communities, it could be a mechanism offsetting evaporation losses. Tillandsia recurvata is a cosmopolitan epiphyte adapted to arid habitats where fog may be an important water source. Therefore, the interception storage capacity by T. recurvata was measured in controlled conditions and applying simulated rain or fog. Juvenile, vegetative specimens were used to determine the potential upperbound storage capacities. The storage capacity was proportional to dry weight mass. Interception storage capacity (Cmin) was 0.19 and 0.56 mm for rainfall and fog respectively. The coefficients obtained in the laboratory were used together with biomass measurements for T. recurvata in a xeric scrub to calculate the depth of water intercepted by rain. T. recurvata contributed 20 % to the rain interception capacity of their shrub hosts: Acacia farnesiana and Prosopis laevigata and; also potentially intercepted 4.8 % of the annual rainfall. Nocturnal stomatic opening in T. recurvata is not only relevant for CO2 but for water vapor, as suggested by the higher weight change of specimens wetted with fog for 1 h at dark in comparison to those wetted during daylight (543 ± 77 vs. 325 ± 56 mg, p = 0.048). The storage capacity of T. recurvata leaf surfaces could increase the amount of water available for evaporation, but as this species colonise montane forests, the effect could be negative on water recharge, because potential storage capacity is very high, in the laboratory experiments it took up to 12 h at a rate of 0.26 l h-1 to reach saturation conditions when fog was applied.

  3. Utility fog: A universal physical substance

    NASA Technical Reports Server (NTRS)

    Hall, J. Storrs

    1993-01-01

    Active, polymorphic material ('Utility Fog') can be designed as a conglomeration of 100-micron robotic cells ('foglets'). Such robots could be built with the techniques of molecular nanotechnology. Controllers with processing capabilities of 1000 MIPS per cubic micron, and electric motors with power densities of one milliwatt per cubic micron are assumed. Utility Fog should be capable of simulating most everyday materials, dynamically changing its form and properties, and forms a substrate for an integrated virtual reality and telerobotics.

  4. A model for predicting fog aerosol size distributions

    NASA Astrophysics Data System (ADS)

    Rudiger, Joshua J.; Book, Kevin; Baker, Brooke; deGrassie, John Stephen; Hammel, Stephen

    2016-09-01

    An accurate model and parameterization of fog is needed to increase the reliability and usefulness of electro-optical systems in all relevant environments. Current models vary widely in their ability to accurately predict the size distribution and subsequent optical properties of fog. The Advanced Navy Aerosol Model (ANAM), developed to model the distribution of aerosols in the maritime environment, does not currently include a model for fog. One of the more prevalent methods for modeling particle size spectra consists of fitting a modified gamma function to fog measurement data. This limits the fog distribution to a single mode. Here we establish an empirical model for predicting complicated multimodal fog droplet size spectra using machine learning techniques. This is accomplished through careful measurements of fog in a controlled laboratory environment and measuring fog particle size distributions during outdoor fog events.

  5. Measuring mercury in coastal fog water

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2012-04-01

    Mercury, a heavy metal neurotoxin, accumulates in sea life, in some cases reaching levels that make seafood unsafe for humans to eat. How mercury gets into aquatic organisms is debated, but part of the pathway could include mercury carried in precipitation, including rain, snow, and fog. The contribution of mercury in fog water in particular is not well known, especially in foggy coastal areas such as coastal California. To learn more, Weiss-Penzias et al. measured total mercury and monomethyl mercury concentrations in fog water and rainwater samples taken from four locations around Monterey Bay, California, during spring and summer 2011. They found that the mean monomethyl mercury concentrations in their fog water samples were about 34 times higher than the mean concentrations in their rainwater samples. Therefore, the authors believe that fog is an important, previously unrecognized source of mercury to coastal ecosystems. They also explored potential sources of mercury, finding that biotically formed monomethyl mercury from oceanic upwelling may contribute to monomethyl mercury in fog. (Geophysical Research Letters, doi:10.1029/2011GL050324, 2012)

  6. Evolution and Advection of Solar Mesogranulation

    DTIC Science & Technology

    1992-03-01

    unprecedented clarity. We see that the supergranules, which are known to carry along (advect) the granules with their convective motion, also advect...I Solar mesogranulation, Solar observations, Solar super- 2 granulation 16. PRICE COCE 1i7. SECJ-3T LSiIATO 8 EUITY CLASSIFICA ION 19. SECURITY CLAS...mo~iesý sho~ed that granules are adl~ectedl b• Richard Muller*, Hers& Auffret*, Thierry Roudiert, the larger-scale consectie flowss. and thu, could

  7. PAFOG—a new efficient forecast model of radiation fog and low-level stratiform clouds

    NASA Astrophysics Data System (ADS)

    Bott, Andreas; Trautmann, Thomas

    The new one-dimensional forecast model PAFOG for radiation fogs and low-level stratiform clouds will be presented. The aim of the model is to improve the local visibility forecast on airports and other traffic locations where fog and low-level stratus frequently occur. PAFOG has been developed on the basis of the microphysical fog model MIFOG of Bott et al. [J. Atmos. Sci. 47 (1990) 2153]. To obtain a numerically efficient model, the detailed spectral cloud microphysics of MIFOG has been replaced by the parameterization scheme of Chaumerliac et al. [J. Geophys. Res. 92 (1987) 3114]. Furthermore, according to Siebert et al. [Beitr. Phys. Atmos. 65 (1992a) 93], a model for low vegetation is included in PAFOG so that now fog evolution as influenced by different types of vegetation can also be accounted for. The performance of PAFOG has been tested by comparing the model results with routine observations of the German Weather Service. Nine different weather periods comprising a total of 45 days have been investigated. In 41 cases, PAFOG yields agreement with the observations in terms of occurrence or nonoccurrence of fog or stratiform clouds. During radiation fogs, the calculated and observed visibilities are quite similar. However, in the model simulations the formation of dense fogs tends to be somewhat delayed. From the case studies with stratiform clouds, it is seen that cloud evolution in time and space strongly depends on the value of the large-scale subsidence. Since this quantity is not available from measurements, it must be provided by means of a numerical weather forecast model.

  8. Adjusting soil water balance calculations for light rainfall, dew, and fog.

    NASA Astrophysics Data System (ADS)

    Snyder, R. L.; Spano, D.; Moratiel, R.

    2012-04-01

    The main sources of water for an irrigated crop include irrigation applications, precipitation, water tables, fog interception, and dew formation. For a well-drained soil in a climate where there are a few events of fog, dew, or light rainfall, computing a water balance is relatively easy, but it is complicated in regions characterized by considerable events of fog, dew and light rainfall. In these regions, growers are hesitant to use ET-Based scheduling because the cumulative crop evapotranspiration is often considerably higher than the soil water depletion. We will present a simple and practical procedure to estimate the contribution of fog interception, dew, and light rainfall to daily crop evapotranspiration in California and to show how to use the information to improve water balance calculations for efficient water use in irrigation. It is assumed that the relationship between normalized hourly ETo and time of the day is similar to the relationship between normalized hourly ETc and time of the day. We can describe the change in soil water depletion (ΔDSW) on that day as: ΔDsw =ETc x F where F is the fraction of ETc coming from the soil, and F is determined using the expression: F = --1--- 1+ e(t-11.265.5) Where t is the approximate local standard time in hours when the crop dries. This simple method improves water balance scheduling and the adoption of the ET-based scheduling method in microclimates where fog, dew, and light rainfall are common.

  9. Fog as a Potential Indicator of a Local Water Source in Valles Marineris

    NASA Astrophysics Data System (ADS)

    Leung, Cecilia W. S.; Rafkin, Scot C. R.; McEwen, Alfred S.

    2016-10-01

    Images from Mars Express suggest that water ice fog may be present in Valles Marineris while absent from the surrounding plateau. Using a regional atmospheric model, we investigate planetary boundary layer processes and discuss the implications of these potential water ice fog. Results from our simulations show that the temperature inside Valles Marineris appears warmer relative to the plateaus outside at all times of day. From the modeled temperatures, we calculate saturation vapor pressures and saturation mixing to determine the amount of water vapor in the atmosphere for cloud formation. For a well-mixed atmosphere, saturated conditions in the canyon imply supersaturated conditions outside the canyon where it is colder. Consequently, low clouds should be everywhere. This is generally not the case. Based on potential fog observations inside the canyon, if we assume the plateau is just sub-saturated, and the canyon bottom is just saturated, the resulting difference in mixing ratios represents the minimum amount of vapor required for the atmosphere to be saturated, and for potential fog to form. Under these conditions, we determined that the air inside the canyon would require a 4-7 times enrichment in water vapor at saturation compared to outside the canyon. This suggests a local source of water vapor is required to explain water ice fog appearing within the confines of Valles Marineris on Mars.

  10. Surfzone alongshore advective accelerations: observations and modeling

    NASA Astrophysics Data System (ADS)

    Hansen, J.; Raubenheimer, B.; Elgar, S.

    2014-12-01

    The sources, magnitudes, and impacts of non-linear advective accelerations on alongshore surfzone currents are investigated with observations and a numerical model. Previous numerical modeling results have indicated that advective accelerations are an important contribution to the alongshore force balance, and are required to understand spatial variations in alongshore currents (which may result in spatially variable morphological change). However, most prior observational studies have neglected advective accelerations in the alongshore force balance. Using a numerical model (Delft3D) to predict optimal sensor locations, a dense array of 26 colocated current meters and pressure sensors was deployed between the shoreline and 3-m water depth over a 200 by 115 m region near Duck, NC in fall 2013. The array included 7 cross- and 3 alongshore transects. Here, observational and numerical estimates of the dominant forcing terms in the alongshore balance (pressure and radiation-stress gradients) and the advective acceleration terms will be compared with each other. In addition, the numerical model will be used to examine the force balance, including sources of velocity gradients, at a higher spatial resolution than possible with the instrument array. Preliminary numerical results indicate that at O(10-100 m) alongshore scales, bathymetric variations and the ensuing alongshore variations in the wave field and subsequent forcing are the dominant sources of the modeled velocity gradients and advective accelerations. Additional simulations and analysis of the observations will be presented. Funded by NSF and ASDR&E.

  11. 7. Fog signal house and shed, view south, north and ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. Fog signal house and shed, view south, north and west sides of fog signal house, northeast and northwest sides of shed - Whitehead Light Station, Whitehead Island, East northeast of Tenants Harbor, Spruce Head, Knox County, ME

  12. Potential bronchoconstrictor stimuli in acid fog

    SciTech Connect

    Balmes, J.R.; Fine, J.M.; Gordon, T.; Sheppard, D.

    1989-02-01

    Acid fog is complex and contains multiple stimuli that may be capable of inducing bronchoconstriction. These stimuli include sulfuric and nitric acids, the principal inorganic acids present; sulfites, formed in the atmosphere as a reaction product of sulfur dioxide and water droplets; fog water itself, a hypoosmolar aerosol; the organic acid hydroxymethanesulfonate, the bisulfite adduct of formaldehyde; and gaseous pollutants, e.g., sulfur dioxide, oxides of nitrogen, ozone. Given this complexity, evaluation of the respiratory health effects of naturally occurring acid fog requires assessment of the bronchoconstrictor potency of each component stimulus and possible interactions among these stimuli. We summarize the results of three studies that involve characterization of the bronchoconstrictor potency of acid fog stimuli and/or their interaction in subjects with asthma. The results of the first study indicate that titratable acidity appears to be a more important stimulus to bronchoconstriction than is pH. The results of the second study demonstrate that sulfite species are capable of inducing bronchoconstriction, especially when inhaled at acid pH. The results of the third study suggest that acidity can potentiate hypoosmolar fog-induced bronchoconstriction.

  13. Fog chemistry at an urban midwestern site

    SciTech Connect

    Muir, P.S.; Wade, K.A.; Carter, B.H.; Armentano, T.V.; Pribush, R.A.

    1986-12-01

    The Holcomb Research Institute is monitoring fog chemistry in Indianapolis, Indiana and at sites in and near the heavily industrialized Ohio River Valley. Results reported here indicate that fogs in this area can be strongly acidic, and that further studies are warranted. We report 1) the ionic composition of three fog events, samples collected in Indianapolis between December 1985 and February 1986, and 2) the pH of three additional events, samples collected between November 1985 and February 1986. (The volume of fog collected during the latter three events was insufficient for chemical analysis other than pH.) The pH of the fog samples ranged from 2.85 to 4.06; some of this fell within the range known to damage foliage and yield of some plant species. It has been demonstrated that even one exposure to highly acidic mists (pH par. delta 2.5) can damage certain crop species; hence, it is important to document the occurrence of any events having acidity near this level.

  14. Long-term observation of fog chemistry and estimation of fog water and nitrogen input via fog water deposition at a mountainous site in Hokkaido, Japan

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Takashi; Katata, Genki; Noguchi, Izumi; Sakai, Shigekatsu; Watanabe, Yoko; Uematsu, Mitsuo; Furutani, Hiroshi

    2015-01-01

    To evaluate water and nitrogen input via fog deposition, the fog water chemistry and deposition around a crater lake (Lake Mashu) in northern Japan were investigated in the growing seasons of trees (summer to autumn) in 2006-2012. The fog samples were collected using an active fog collector and droplet size distribution was measured with a droplet size spectrometer (FM-100). The visibility (VIS)-liquid water content of fog (LWC) relationship differed between summer and autumn. Large fog droplets decreased in autumn and the calculated LWC from FM-100 measurements (LWCobs) were lower than those in summer at the same VIS. Two empirical curves between LWCobs and VIS were obtained and used for better estimation of fog deposition. Fog deposition was calculated from LWC empirically derived from past VIS data and deposition velocity (Vd) estimated using wind speed and vegetation parameters. The mean pH of fog water was 4.6 and the percentage of samples of pH 4.0 or more was 93%. Compared to previous literature of exposure experiments of acid mist on plants, fog acidity in this study did not seem to injure plant leaves. The water input via fog deposition accumulated for each growing season was estimated at 107-140 mm, corresponding to 18-23% of the precipitation in the same period. Nitrogen deposition via fog deposition in a plant growing season was estimated at 26-30 meq m- 2 (3.6-4.2 kg N ha- 1). As a long-term trend, NO3- concentration in fog water decreased significantly. However, the long-term trends of fog and nitrogen depositions were not clear.

  15. Anti-fog composition. [for prevention of fogging on surfaces such as space helmet visors and windshields

    NASA Technical Reports Server (NTRS)

    Morrison, H. D.; Carmin, D. L., Jr. (Inventor)

    1974-01-01

    An anti-fog composition is described for the prevention of fogging on surfaces such as space helmet visors, spacecraft windows, and windshields. It is composed of a surface active agent, water, and an oil time extender.

  16. An Empirical Model of the Vertical Structure of German Fogs.

    DTIC Science & Technology

    1980-11-01

    on reveree side if neceesay end Identify by block number) German fogs Vertical variation Fog density Liquid water content Empirical model SAIISTACT...Grafenw6hr and Meppen, Germany. Curve fitting procedures were applied to the results of liquid water content calculations and extinction coefficients...THE ALGORITM ............................................. 7 COMPARISON OF MEASURED AND MODELED FOG DENSITY ........................... 8 CONCLUSIONS

  17. Fog water collection under sea breeze conditions in the Western Mediterranean basin (Valencia region, Spain)

    NASA Astrophysics Data System (ADS)

    Azorin-Molina, C.; Corell, D.; Estrela, M. J.; Valiente, J. A.

    2010-07-01

    Orographic fog occurrences associated with sea breezes determine water collection potential over the mountain ranges near the Mediterranean coast of the Iberian Peninsula. Previous works have confirmed that the effect of sea breezes on cloud genera is to increase the frequency of low (Stratus) and convective (Cumulus) clouds. The primary impact of sea breeze flows corresponds to low stratiform clouds (Stratus, St, and Stratocumulus, Sc) formed in the convective internal boundary layer due to the inflow of moist sea air at lower levels. The formation of Sc clouds is caused by the rising and cooling of turbulent moist sea air over the highest slopes of the mountains at the end of the day. In the most Sc formation, we also observed dense fog banks of Stratus nebulosus (St neb) and dew during the early next morning, covering the inland topographical depressions. The aim of this study is to statistically analyze the impact of sea breezes on fog water collection in the convective internal boundary layer. The study area is located in the eastern of the Iberian Peninsula (Valencia region, Spain) and the survey corresponds to a 7-yr study period (2003-2009). This research is based upon a small network of eight passive fog water collectors distributed over 6 coastal- and 2 inland-mountain areas. A cylindrical fog water instrument (i.e. omnidirectional collection efficiency) based on the ASRC (Atmospheric Science Research Centre, State University of New York) string collector is used to sample fog water volumes on a daily basis. These stations also sampled temperature, humidity, wind speed and direction and precipitation measurements. The current study used these meteorological measurements to apply an automated and manual selection methodologies for identifying past sea breeze episodes. The dataset created by means of these selection techniques allows for the study of fog water volumes associated with sea breeze situations. A detailed statistical characterization of the

  18. Fog, cloud, and dew chemistry. Final report

    SciTech Connect

    Hoffmann, M.R.

    1989-02-28

    The spatial and temporal variations of fog/cloud chemistry were determined in the San Joaquin Valley, in the Los Angeles Basin, and in the Santa Barbara Channel area using automated fog- and cloudwater collectors that were designed and constructed for the project. A significant correlation was observed between the average nighttime cloud- and fogwater loadings of H/sup +/ and NO/sub 3//sup /minus// and the maximum levels of O/sub 3//sup /minus//. Higher aldehydes, a series of dicarbonyls, and a variety of sulfonic acid salts formed by reaction of S(IV) and aldehydes were quantitatively determined in the droplet phase.

  19. 20 years of KVH fiber optic gyro technology: the evolution from large, low performance FOGs to compact, precise FOGs and FOG-based inertial systems

    NASA Astrophysics Data System (ADS)

    Napoli, Jay

    2016-05-01

    Precision fiber optic gyroscopes (FOGs) are critical components for an array of platforms and applications ranging from stabilization and pointing orientation of payloads and platforms to navigation and control for unmanned and autonomous systems. In addition, FOG-based inertial systems provide extremely accurate data for geo-referencing systems. Significant improvements in the performance of FOGs and FOG-based inertial systems at KVH are due, in large part, to advancements in the design and manufacture of optical fiber, as well as in manufacturing operations and signal processing. Open loop FOGs, such as those developed and manufactured by KVH Industries, offer tactical-grade performance in a robust, small package. The success of KVH FOGs and FOG-based inertial systems is due to innovations in key fields, including the development of proprietary D-shaped fiber with an elliptical core, and KVH's unique ThinFiber. KVH continually improves its FOG manufacturing processes and signal processing, which result in improved accuracies across its entire FOG product line. KVH acquired its FOG capabilities, including its patented E•Core fiber, when the company purchased Andrew Corporation's Fiber Optic Group in 1997. E•Core fiber is unique in that the light-guiding core - critical to the FOG's performance - is elliptically shaped. The elliptical core produces a fiber that has low loss and high polarization-maintaining ability. In 2010, KVH developed its ThinFiber, a 170-micron diameter fiber that retains the full performance characteristics of E•Core fiber. ThinFiber has enabled the development of very compact, high-performance open-loop FOGs, which are also used in a line of FOG-based inertial measurement units and inertial navigation systems.

  20. Fog Events at Maceio Airport on the Northern Coast of Brazil During 2002-2005 and 2007

    NASA Astrophysics Data System (ADS)

    Fedorova, Natalia; Levit, Vladimir; de Souza, José Leonaldo; Silva, Aliton Oliveira; Afonso, Joao M. Sousa; Teodoro, Iedo

    2015-10-01

    There were eight fog events in five years at Maceio international airport on the northern coast of Brazil, and all were analyzed. Fog duration was short and its intensity was weak or moderate. The principal objectives of the study were: (1) analysis of the physical processes of fog formation (synoptic and thermodynamic conditions and processes), (2) PAFOG model testing, and (3) estimation of the effect of vegetation on fog forecast. Cyclonic curvature and divergence of the air current over the ocean at low levels and anticyclonic curvature at high levels were associated with the fog. Weak lifting at low levels was identified by the NCEP/DOE II, ECMWF, and WRF models for all eight events. Sinking at high levels was dominant in the ECMWF and WRF models. Absence of thermal inversion and conditional instability at low levels was identified by the NCEP/DOE II and ECMWF models. According to the WRF model a typical temperature profile during fog comprises three layers: (1) a very thin layer (up to 166 m, 985 hPa) of temperature inversion with very high humidity; (2) a conditional layer of instability from 985-860 hPa; and (3) a dry and stable layer above 860 hPa. Moderate fog with visibility between 200 and 300 m was associated with ocean cooling whereas weak fog was associated with ocean warming. A warm oscillation on the sea surface near the Brazilian northeast was observed for all fog events. It was found there was colder air over the warmer water near the coast. Weak confluence in troughs at low levels contributes to weak lifting at low levels. This current creates conditions resulting in humidity increase. A warmer sea surface contributes to more evaporation and, as a consequence, increases the amount of water vapor in the surrounding air at low levels near the coast. The PAFOG model was used to forecast the fog for three events (i.e., for all cases possible), and was satisfactory for two cases. Satisfactory results for fog duration and intensity were obtained with 9

  1. Diffusion and Advection using Cellular Potts Model

    NASA Astrophysics Data System (ADS)

    Dan, Debasis; Glazier, James

    2005-03-01

    The Cellular Potts Model (CPM) is a robust cell level methodology for simulation of biological tissues and morphogenesis. Standard diffusion solvers in the CPM use finite difference methods on the underlying CPM lattice. These methods have difficulty in simulating local advection in the ECM due to physiology and morphogenesis. To circumvent the problem of instabilities we simulate advection-diffusion within the framework of CPM using off-lattice finite-difference methods. We define a set of generalised fluid "cells" or particles which separate advection and diffusion from the lattice. Diffusion occurs between neighboring fluid cells by local averaging rules which approximate the Laplacian. CPM movement of the cells by spin flips handles the advection. The extension allows the CPM to model viscosity explicitly by including a relative velocity constraint on the fluid. The extended CPM correctly reproduces flow profiles of viscous fluids in cylindrical tube, during Stokes flow across a sphere and in flow in concentric cylindrical shells. We illustrate various conditions for diffusion including multiple instantaneous sources, continuous sources, moving sources and different boundary geometries and conditions to validate our approximation by comparing with analytical and established numerical solutions.

  2. 3D Flow Visualization Using Texture Advection

    NASA Technical Reports Server (NTRS)

    Kao, David; Zhang, Bing; Kim, Kwansik; Pang, Alex; Moran, Pat (Technical Monitor)

    2001-01-01

    Texture advection is an effective tool for animating and investigating 2D flows. In this paper, we discuss how this technique can be extended to 3D flows. In particular, we examine the use of 3D and 4D textures on 3D synthetic and computational fluid dynamics flow fields.

  3. An assessment of warm fog: Nucleation, control, and recommended research

    NASA Technical Reports Server (NTRS)

    Corrin, M. L.; Connell, J. R.; Gero, A. J.

    1974-01-01

    A state-of-the-art survey is given of warm fog research which has been performed up to, and including, 1974. Topics covered are nucleation, growth, coalescence, fog structures and visibility, effects of surface films, drop size spectrum, optical properties, instrumentation, liquid water content, condensation nuclei. Included is a summary of all reported fog modification experiments. Additional data is provided on air flow, turbulence, a summary of recommendations on instruments to be developed for determining turbulence, air flow, etc., as well as recommendations of various fog research tasks which should be performed for a better understanding of fog microphysics.

  4. Warm fog dissipation using large volume water sprays

    NASA Technical Reports Server (NTRS)

    Keller, Vernon W. (Inventor)

    1988-01-01

    To accomplish the removal of warm fog about an area such as an airport runway, a plurality of nozzles along a line adjacent the area propelled water jets through the fog to heights of approximately twenty-five meters. Each water jet breaks up forming a water drop size distribution that falls through the fog overtaking, colliding, and coalescing with individual fog droplets and thereby removes the fog. A water retrieval system is used to collect the water and return it to reservoirs for pumping it to the nozzles once again.

  5. Spatiotemporal Variability of Surface Meteorological Variables During Fog and No-Fog Events in the Heber Valley, UT; Selected Case Studies From MATERHORN-Fog

    NASA Astrophysics Data System (ADS)

    van den Bossche, Michael; De Wekker, Stephan F. J.

    2016-09-01

    We investigated the spatiotemporal variability of surface meteorological variables in the nocturnal boundary layer using six automatic weather stations deployed in the Heber Valley, UT, during the MATERHORN-Fog experiment. The stations were installed on the valley floor within a 1.5 km × 0.8 km area and collected 1-Hz wind and pressure data and 0.2-Hz temperature and humidity data. We describe the weather stations and analyze the spatiotemporal variability of the measured variables during three nights with radiative cooling. Two nights were characterized by the presence of dense ice fog, one night with a persistent (`heavy') fog, and one with a short-lived (`moderate') fog, while the third night had no fog. Frost-point depressions were larger preceding the night without fog and showed a continued decrease during the no-fog night. On both fog nights, the frost-point depression reached values close to zero early in the night, but ~5 h earlier on the heavy-fog night than on the moderate-fog night. Spatial variability of temperature and humidity was smallest during the heavy-fog night and increased temporarily during short periods when wind speeds increased and the fog lifted. During all three nights, wind speeds did not exceed 2 m/s. The temporal variability of the wind speed and direction was larger during the fog nights than during the no-fog nights, but was particularly large during the heavy-fog night. The large variability corresponded with short-lived (5-10 min) pressure variations with amplitudes on the order of 0.5 hPa, indicating gravity wave activity. These pressure fluctuations occurred at all stations and were correlated in particular with variability in wind direction. Although not able to provide a complete picture of the nocturnal boundary layer, our low-cost weather stations were able to continuously collect data that were comparable to those of nearby research-grade instruments. From these data, we distinguished between fog and no-fog events

  6. Physical and Chemical Characterization of Military Smokes. Part 2. Fog Oils and Oil Fogs

    DTIC Science & Technology

    1980-06-01

    almost equal amounts of aljPhatic and aromatic hydrocarbons with acids, alcohols and esters at the 1seV ee’ level or less and nitrogen derivatives in...fogs were separated into class fractions of aliphatics, aromatics, alcohols , acids and esters. The aliphatic and aromatic fractions predominated in...No. 3 and Corresponding Oil Fogs. . B-30 Chart 17. Alcohol Fraction: Oil No. 1 and Corresponding Oil Foys . B-31 Chart 18. Alcohol Fraction: Oil No

  7. First Results From a Dynamic Fog Climatology Modeling System

    NASA Astrophysics Data System (ADS)

    O'Brien, T. A.; Sloan, L.; Chuang, P. Y.; Faloona, I. C.; Snyder, M. A.; Rossiter, D. L.

    2010-12-01

    We have coupled a new boundary layer model to a regional climate model (RegCM4) in order to dynamically (as opposed to empirically) simulate marine stratocumulus and coastal fog. We drive the coupled RCM with NCEP's new 20th Century reanalysis dataset in order to simulate a 120 year climatology of coastal fog. Even at relatively coarse resolution (50 km) this fog modeling system exhibits significant skill in simulating the interannual variability and long-term trends that have been observed in summertime fog on California's coast. In agreement with results from Johnstone and Dawson (2010), we simulate a high correlation between fog variability in Monterey and Arcata (in addition to other locations along California's coast), which indicates that interannual fog variability is driven by large-scale forcing. Preliminary results suggest that a trend in this same large-scale forcing is also responsible for the century-long decline of summertime coastal fog.

  8. Fog/cloud and rain chemistry in northern coastal California

    SciTech Connect

    Bicknell, S.H.; Lemcke, S.

    1987-07-01

    Fog, clouds and rain were sampled for 2 years at Redwood National Park (RNP) and one year at Arcata and Oakland. Fog and cloud water samples were more acidic and contained higher concentrations of Ca, Mg, K, Na, NH4, SO4, NO3 and Cl, than rain samples at all sites. Cloud/fog water and rain sample chemistry was not different for RNP and Arcata; but Oakland samples were significantly more acid and had higher concentrations of all elements. RNP and Arcata cloud/fog samples were more acid and contained higher elemental concentrations than expected under pristine conditions. Average pH's were: RNP cloud/fog - 4.12, RNP rain - 4.63, Arcata cloud/fog - 4.00, Arcata rain - 4.66, Oakland cloud/fog - 3.87, Oakland rain - 4.37.

  9. Musings on Willower's "Fog": A Response.

    ERIC Educational Resources Information Center

    English, Fenwick

    1998-01-01

    Professor Willower complains about the "fog" encountered in postmodernist literature and the author's two articles in "Journal of School Leadership." On closer examination, this miasma is simply the mildew on Willower's Cartesian glasses. Educational administration continues to substitute management and business fads for any…

  10. Holographic Imaging In Dense Artificial Fog

    NASA Technical Reports Server (NTRS)

    Liu, Hua-Kuang; Marzwell, Neville

    1996-01-01

    Artificial fog serves as volume-projection medium for display of three-dimensional image. Projection technique enables display of images for variety of purposes, possibly including entertainment, indoor and outdoor advertising, medical diagnostics and image representations for surgical procedures, and education.

  11. Rooftop dew, fog and rain collection in southwest Morocco and predictive dew modeling using neural networks

    NASA Astrophysics Data System (ADS)

    Lekouch, Imad; Lekouch, Khalid; Muselli, Marc; Mongruel, Anne; Kabbachi, Belkacem; Beysens, Daniel

    2012-07-01

    SummaryTwo coastal sites were investigated in an arid region of southwest Morocco to determine the amount of dew, fog and rain that could be collected from rooftops for household use. Systematic measurements were performed in Mirleft (43 m asl, 200 m from the coast) for 1 year (May 1, 2007 to April 30, 2008) and in Id Ouasskssou (240 m asl, 8 km from the coast) for three summer months (July 1, 2007 to September 30, 2007). Dew water was collected using standard passive dew condensers and fog water by utilizing planar fog collectors. The wind flow was simulated on the rooftop to establish the location of the fog collector. At both sites, dew yields and, to a lesser extent, fog water yields, were found to be significant in comparison to rain events. Mirleft had 178 dew events (48.6% of the year, 18 ± 2 L m-2 cumulated amount) and 20 fog episodes (5.5% of the year, 1.4 L m-2 with uncertainty -0.2/+0.4 L m-2 cumulated amount), corresponding to almost 40% of the yearly rain contribution (31 rain events, 8.5% of the year, 49 ± 7 mm cumulated amount). At Id Ouasskssou there were 50 dew events (7.1 ± 0.3 L m-2, 54.3% frequency), 16 fog events (6.5 L m-2 with uncertainty -0.1/+1.8 L m-2, 17.4% frequency) and six rain events (16 ± 2 mm, 6.5% frequency). Meteorological data (air and dew point temperature and/or relative humidity, wind speed and wind direction, cloud cover) were recorded continuously at Mirleft to assess the influence of local meteorological conditions on dew and fog formation. Using the set of collected data, a new model for dew yield prediction based on artificial neural networks was developed and tested for the Mirleft site. This model was then extrapolated to 15 major cities in Morocco to assess their potential for dew water collection. It was found that the location of the cities with respect to the Atlas mountain chain, which controls the circulation of the humid marine air, is the main factor that influences dew production.

  12. Coalescence of fog droplets: Differential fog water deposition on wet and dry forest canopies

    NASA Astrophysics Data System (ADS)

    Tobón, C.; Barrero, J.

    2010-07-01

    The Páramo ecosystem is a high-altitude (2800 - 4500 masl), natural ecosystems which comprises approximately 42000 km2, extending across the Andes from north of Peru, Ecuador, Colombia and western part of Venezuela. Andean páramos are widely considered to be prime suppliers of large volumes of high-quality water for large cities and for hydropower production. As páramos tend to be subjected to persistent fog incidence, fog interception by the vegetation is a common process in these ecosystems, representing not only an extra input of water to the ecosystem but also to suppress evaporation. In this process, small drops of water, transported by the wind, are captured by the surfaces of the vegetation, acting as physical obstacles to the flow of fog. These drops condense in the exposed surfaces and drip towards the ground or evaporate from the surfaces. The quantification of the magnitude of these processes is important for the quantification of the water balance of river basins where these types of ecosystems exist. Although the great hydrological importance of fog in montane tropical ecosystems little is known about its physical principles related to the interception of fog by physical barriers as vegetation, notably the differential behaviour of a wet and dry vegetation in the efficiency of capturing water from the fog. To characterize and quantify this efficiency of páramo vegetation in capturing water from the fog, during wet and dry canopy conditions, an experimental design was set up at the Páramo de Chingaza (Colombia) where paired samples of espeletia branches (dry and wet) were exposed to different fog events, and at the same time Juvik cylinders were exposed by the side of the experimental site, to measured fog inputs. Cylinders were also paired (wet and dry) at the beginning of the experiments. Results indicated that exposed wet and dry samples have a significant difference on the magnitude of water intercepted from the fog, being, in average, the wet

  13. Capillary deposition of advected floating particles

    NASA Astrophysics Data System (ADS)

    Dressaire, Emilie; Debaisieux, Aymeric; Gregori, Federico

    2016-11-01

    The deposition and aggregation of particles flowing through a confined environment can dramatically hinder the transport of suspensions. Yet, the mechanisms responsible for the deposition of particles in shear flow are not fully understood. Here, we use an experimental model system in which floating particles are advected on the surface of a water channel and deposited on fixed obstacles through attractive capillary effects. By varying the flow rate of the liquid, the wetting properties and size of the particles and obstacles, we can tune the magnitude of the capillary and hydrodynamic forces that determine the probability of deposition and the equilibrium position on the substrate. We show that arrays of obstacles can be designed to efficiently capture the floating particles advected by the flow.

  14. Effects of synoptic-scale circulation pattern and local land surface condition on fog at Kushiro, northern Japan

    NASA Astrophysics Data System (ADS)

    Sugimoto, S.; Sato, T.; Nakamura, K.

    2012-12-01

    Marine stratiform clouds are frequently observed over western North Pacific offshore of the northeast Japan during summer when warm southerly wind prevails over underlying cold ocean current. Such clouds often migrate over Kushiro located in the coastal area of eastern Hokkaido Island, north Japan and are recognized as sea fog. On the other hand, Kushiro is a middle-sized city with population of over 180,000 and a large wetland expands at the north of Kushiro city. The difference of land surface condition between the city and the wetland might cause heterogeneity of the sea fog distribution over land, via dissipation and regeneration process of fog. In this study, long-term visibility data for Kushiro are investigated to clarify the relationship between interannual variation of fog frequency (FF) and large-scale circulation patterns. Furthermore, frequency of fog/low-level cloud (LC) is identified using satellite images and sensitivity experiments changing land surface condition are conducted using meteorological regional model to understand an impact of land use on the local fog distribution and its physical processes. Monthly mean FF trends observed at Kushiro during 1931 to 2010 shows significant decline (-3.3 day per decade). Since late 1970s, the decline at Kushiro has been particularly remarkable in July and August in association with an increased number of years with very low FF. Analysis of radiosonde data has revealed the development of shallow moist layer under a strong inversion layer during fog occurrence because of abundant moisture supply from southerly wind. However, cold and dry northerly wind prevents the formation of inversion layer during fog-free days. Composite analysis of reanalysis data suggests that the low-level southerly wind toward northeast Japan is weaker in the low FF month of July than climatology owing to a southward shift of the North Pacific High (NPH) and stronger Okhotsk High. In August, eastward displacement or shrinking of the

  15. Distributed Parallel Particle Advection using Work Requesting

    SciTech Connect

    Muller, Cornelius; Camp, David; Hentschel, Bernd; Garth, Christoph

    2013-09-30

    Particle advection is an important vector field visualization technique that is difficult to apply to very large data sets in a distributed setting due to scalability limitations in existing algorithms. In this paper, we report on several experiments using work requesting dynamic scheduling which achieves balanced work distribution on arbitrary problems with minimal communication overhead. We present a corresponding prototype implementation, provide and analyze benchmark results, and compare our results to an existing algorithm.

  16. Efficient mass transport by optical advection

    PubMed Central

    Kajorndejnukul, Veerachart; Sukhov, Sergey; Dogariu, Aristide

    2015-01-01

    Advection is critical for efficient mass transport. For instance, bare diffusion cannot explain the spatial and temporal scales of some of the cellular processes. The regulation of intracellular functions is strongly influenced by the transport of mass at low Reynolds numbers where viscous drag dominates inertia. Mimicking the efficacy and specificity of the cellular machinery has been a long time pursuit and, due to inherent flexibility, optical manipulation is of particular interest. However, optical forces are relatively small and cannot significantly modify diffusion properties. Here we show that the effectiveness of microparticle transport can be dramatically enhanced by recycling the optical energy through an effective optical advection process. We demonstrate theoretically and experimentally that this new advection mechanism permits an efficient control of collective and directional mass transport in colloidal systems. The cooperative long-range interaction between large numbers of particles can be optically manipulated to create complex flow patterns, enabling efficient and tunable transport in microfluidic lab-on-chip platforms. PMID:26440069

  17. Referenceless Prediction of Perceptual Fog Density and Perceptual Image Defogging.

    PubMed

    Choi, Lark Kwon; You, Jaehee; Bovik, Alan Conrad

    2015-11-01

    We propose a referenceless perceptual fog density prediction model based on natural scene statistics (NSS) and fog aware statistical features. The proposed model, called Fog Aware Density Evaluator (FADE), predicts the visibility of a foggy scene from a single image without reference to a corresponding fog-free image, without dependence on salient objects in a scene, without side geographical camera information, without estimating a depth-dependent transmission map, and without training on human-rated judgments. FADE only makes use of measurable deviations from statistical regularities observed in natural foggy and fog-free images. Fog aware statistical features that define the perceptual fog density index derive from a space domain NSS model and the observed characteristics of foggy images. FADE not only predicts perceptual fog density for the entire image, but also provides a local fog density index for each patch. The predicted fog density using FADE correlates well with human judgments of fog density taken in a subjective study on a large foggy image database. As applications, FADE not only accurately assesses the performance of defogging algorithms designed to enhance the visibility of foggy images, but also is well suited for image defogging. A new FADE-based referenceless perceptual image defogging, dubbed DEnsity of Fog Assessment-based DEfogger (DEFADE) achieves better results for darker, denser foggy images as well as on standard foggy images than the state of the art defogging methods. A software release of FADE and DEFADE is available online for public use: http://live.ece.utexas.edu/research/fog/index.html.

  18. An analysis of fog events at Belgrade International Airport

    NASA Astrophysics Data System (ADS)

    Veljović, Katarina; Vujović, Dragana; Lazić, Lazar; Vučković, Vladan

    2015-01-01

    A preliminary study of the occurrence of fog at Belgrade "Nikola Tesla" Airport was carried out using a statistical approach. The highest frequency of fog has occurred in the winter months of December and January and far exceeded the number of fog days in the spring and the beginning of autumn. The exceptionally foggy months, those having an extreme number of foggy days, occurred in January 1989 (18 days), December 1998 (18 days), February 2005 (17 days) and October 2001 (15 days). During the winter months (December, January and February) from 1990 to 2005 (16 years), fog occurred most frequently between 0600 and 1000 hours, and in the autumn, between 0500 and 0800 hours. In summer, fog occurred most frequently between 0300 and 0600 hours. During the 11-year period from 1995 to 2005, it was found that there was a 13 % chance for fog to occur on two consecutive days and a 5 % chance that it would occur 3 days in a row. In October 2001, the fog was observed over nine consecutive days. During the winter half year, 52.3 % of fog events observed at 0700 hours were in the presence of stratus clouds and 41.4 % were without the presence of low clouds. The 6-h cooling observed at the surface preceding the occurrence of fog between 0000 and 0700 hours ranged mainly from 1 to 4 °C. A new method was applied to assess the probability of fog occurrence based on complex fog criteria. It was found that the highest probability of fog occurrence (51.2 %) takes place in the cases in which the relative humidity is above 97 %, the dew-point depression is 0 °C, the cloud base is lower than 50 m and the wind is calm or weak 1 h before the onset of fog.

  19. GOES-derived fog and low cloud indices for coastal north and central California ecological analyses

    NASA Astrophysics Data System (ADS)

    Torregrosa, Alicia; Combs, Cindy; Peters, Jeff

    2016-02-01

    Fog and low cloud cover (FLCC) strongly influences the water, energy, and nutrient flux of coastal ecosystems. Easy-to-use FLCC data are needed to quantify the impacts of FLCC on ecosystem dynamics especially during hot and dry Mediterranean climate summers. Monthly, annual, and decadal FLCC digital maps (indices) were derived for June-September 1999-2009 for coastal California, latitude 34.50°N (south of Monterey Bay) to latitude 41.95°N (north of Crescent City) from 26,000 hourly night and day Geostationary Operational Environmental Satellite (GOES) images. Monthly average FLCC ranges from <2 to 18 hours per day (h/d). Average FLCC over the ocean increases from north (9 h/d) to south (14 h/d), whereas on land, FLCC is highest where land juts into the prevailing NW winds and is lowest in the lee of major capes. FLCC advects farthest inland through low-lying NW ocean-facing valleys. At night, average total hours of FLCC are higher more frequently on land than over the ocean. The interannual FLCC coefficient of variation shows long-term geographic stability that is strongly associated with landform position. FLCC hours per day mapped contours, derived from decadal average FLCC, delineate the commonly used term "fog belt" into FLCC zones with increased locational precision. FLCC indices are available for download from the California Landscape Conservation Cooperative Climate Commons website (http://climate.calcommons.org/datasets/summertime-fog). FLCC indices can improve analyses of biogeographic and bioclimatic species distribution models; understanding meteorological mechanisms driving FLCC patterns; solar energy feasibility studies; investigations of ecohydrology, evapotranspiration, and agricultural irrigation demand; and viticulture ripening models.

  20. Extinction of Light during the Fog Life Cycle: a Result from the ParisFog Experiment

    SciTech Connect

    Elias, T.; Haeffelin, M.; Drobinski, P.

    2009-03-11

    Data set acquired by five particle-dedicated instruments set up on the SIRTA experimental site during the ParisFog field campaign are exploited to document microphysical properties of particles contributing to extinction of visible radiation in variable situations. The case study is a 48-hour period when atmospheric conditions are highly variable: relative humidity changes between 50 and 100%, visibility ranges between 35000 and 65 m, the site is either downwind Paris area either under maritime influence. A dense and homogeneous fog formed by radiative cooling during the 18-19 February night. In 7 hours, visibility decreases from 26 000 m to 65 m, because of transported pollution (factor 3 in visibility reduction), aerosol hydration (factor 20) and aerosol activation (factor 6). According to Mie theory, extinction in clear-sky polluted and unpolluted regimes is due equally to Aitken and accumulation modes. Extinction in haze is due to hydrated aerosols distributed in the accumulation mode, for diameter smaller than 2 {mu}m. Hydrated aerosols of the accumulation mode still contribute to 20-30% extinction in the fog. Measurements show that fog droplets, with diameter included between 2 and 10 {mu}m, contribute to 40% extinction during the first hours of the fog.

  1. Environmental fog/rain visual display system for aircraft simulators

    NASA Technical Reports Server (NTRS)

    Chase, W. D. (Inventor)

    1982-01-01

    An environmental fog/rain visual display system for aircraft simulators is described. The electronic elements of the system include a real time digital computer, a caligraphic color display which simulates landing lights of selective intensity, and a color television camera for producing a moving color display of the airport runway as depicted on a model terrain board. The mechanical simulation elements of the system include an environmental chamber which can produce natural fog, nonhomogeneous fog, rain and fog combined, or rain only. A pilot looking through the aircraft wind screen will look through the fog and/or rain generated in the environmental chamber onto a viewing screen with the simulated color image of the airport runway thereon, and observe a very real simulation of actual conditions of a runway as it would appear through actual fog and/or rain.

  2. Fog as a fresh-water resource: overview and perspectives.

    PubMed

    Klemm, Otto; Schemenauer, Robert S; Lummerich, Anne; Cereceda, Pilar; Marzol, Victoria; Corell, David; van Heerden, Johan; Reinhard, Dirk; Gherezghiher, Tseggai; Olivier, Jana; Osses, Pablo; Sarsour, Jamal; Frost, Ernst; Estrela, María J; Valiente, José A; Fessehaye, Gebregiorgis Mussie

    2012-05-01

    The collection of fog water is a simple and sustainable technology to obtain fresh water for afforestation, gardening, and as a drinking water source for human and animal consumption. In regions where fresh water is sparse and fog frequently occurs, it is feasible to set up a passive mesh system for fog water collection. The mesh is directly exposed to the atmosphere, and the foggy air is pushed through the mesh by the wind. Fog droplets are deposited on the mesh, combine to form larger droplets, and run down passing into a storage tank. Fog water collection rates vary dramatically from site to site but yearly averages from 3 to 10 l m(-2) of mesh per day are typical of operational projects. The scope of this article is to review fog collection projects worldwide, to analyze factors of success, and to evaluate the prospects of this technology.

  3. Status of warm fog dispersal research

    NASA Technical Reports Server (NTRS)

    Keller, V. W.

    1985-01-01

    A new concept for dispersing warm fog is presented. This brute force technique uses large volume recycled water sprays. Energy requirements for this technique are an order of magnitude less than those to operate a thermo-kinetic system. An important side benefit is the considerable emergency fire extinguishing capability it provides along the runway. Tests conducted to provide drop spectra measurements and temperature response measurements of suitable water sprays are described. Three mobile firefighting modules capable of spraying up to 630 l/s (10,000 gpm) to a height in excess of 50 m were utilized. Periodic operation of two parallel rows of nozzles in a heavy fog resulted in downwind-correlated increases in the visual range measured with a forward scatter visibility meter.

  4. Fog and rain in the Amazon

    PubMed Central

    Anber, Usama; Gentine, Pierre; Wang, Shuguang; Sobel, Adam H.

    2015-01-01

    The diurnal and seasonal water cycles in the Amazon remain poorly simulated in general circulation models, exhibiting peak evapotranspiration in the wrong season and rain too early in the day. We show that those biases are not present in cloud-resolving simulations with parameterized large-scale circulation. The difference is attributed to the representation of the morning fog layer, and to more accurate characterization of convection and its coupling with large-scale circulation. The morning fog layer, present in the wet season but absent in the dry season, dramatically increases cloud albedo, which reduces evapotranspiration through its modulation of the surface energy budget. These results highlight the importance of the coupling between the energy and hydrological cycles and the key role of cloud albedo feedback for climates over tropical continents. PMID:26324902

  5. Fog and rain in the Amazon

    NASA Astrophysics Data System (ADS)

    Anber, Usama; Gentine, Pierre; Wang, Shuguang; Sobel, Adam H.

    2015-09-01

    The diurnal and seasonal water cycles in the Amazon remain poorly simulated in general circulation models, exhibiting peak evapotranspiration in the wrong season and rain too early in the day. We show that those biases are not present in cloud-resolving simulations with parameterized large-scale circulation. The difference is attributed to the representation of the morning fog layer, and to more accurate characterization of convection and its coupling with large-scale circulation. The morning fog layer, present in the wet season but absent in the dry season, dramatically increases cloud albedo, which reduces evapotranspiration through its modulation of the surface energy budget. These results highlight the importance of the coupling between the energy and hydrological cycles and the key role of cloud albedo feedback for climates over tropical continents.

  6. Carbon speciation and surface tension of fog

    USGS Publications Warehouse

    Capel, P.D.; Gunde, R.; Zurcher, F.; Giger, W.

    1990-01-01

    The speciation of carbon (dissolved/particulate, organic/inorganic) and surface tension of a number of radiation fogs from the urban area of Zurich, Switzerland, were measured. The carbon species were dominated by "dissolved" organic carbon (DOC; i.e., the fraction that passes through a filter), which was typically present at levels of 40-200 mg/L. Less than 10% of the DOC was identified as specific individual organic compounds. Particulate organic carbon (POC) accounted for 26-41% of the mass of the particles, but usually less than 10% of the total organic carbon mass. Inorganic carbon species were relatively minor. The surface tensions of all the measured samples were less than pure water and were correlated with their DOC concentrations. The combination of high DOC and POC and low surface tension suggests a mechanism for the concentration of hydrophobic organic contaminants in the fog droplet, which have been observed by numerous investigators. ?? 1990 American Chemical Society.

  7. Fog and rain in the Amazon.

    PubMed

    Anber, Usama; Gentine, Pierre; Wang, Shuguang; Sobel, Adam H

    2015-09-15

    The diurnal and seasonal water cycles in the Amazon remain poorly simulated in general circulation models, exhibiting peak evapotranspiration in the wrong season and rain too early in the day. We show that those biases are not present in cloud-resolving simulations with parameterized large-scale circulation. The difference is attributed to the representation of the morning fog layer, and to more accurate characterization of convection and its coupling with large-scale circulation. The morning fog layer, present in the wet season but absent in the dry season, dramatically increases cloud albedo, which reduces evapotranspiration through its modulation of the surface energy budget. These results highlight the importance of the coupling between the energy and hydrological cycles and the key role of cloud albedo feedback for climates over tropical continents.

  8. Long-range polarimetric imaging through fog.

    PubMed

    Fade, Julien; Panigrahi, Swapnesh; Carré, Anthony; Frein, Ludovic; Hamel, Cyril; Bretenaker, Fabien; Ramachandran, Hema; Alouini, Mehdi

    2014-06-20

    We report an experimental implementation of long-range polarimetric imaging through fog over kilometric distance in real field atmospheric conditions. An incoherent polarized light source settled on a telecommunication tower is imaged at a distance of 1.3 km with a snapshot polarimetric camera including a birefringent Wollaston prism, allowing simultaneous acquisition of two images along orthogonal polarization directions. From a large number of acquisitions datasets and under various environmental conditions (clear sky/fog/haze, day/night), we compare the efficiency of using polarized light for source contrast increase with different signal representations (intensity, polarimetric difference, polarimetric contrast, etc.). With the limited-dynamics detector used, a maximum fourfold increase in contrast was demonstrated under bright background illumination using polarimetric difference image.

  9. Air Mass Considerations in Fog Optical Modeling.

    DTIC Science & Technology

    1981-02-01

    military forces are increasingly relying on new sophis - ticated weapons systems which employ electro-optical (EO) sensors or systems in their principles of...infrared extinction coefficients. Several authors (Stewart,10 Turner et all’) have shown that models which depend upon visibility alone can lead to...Extinction by Fog, TR-77-9, Technology Laboratory, Physical Science Directorate, Redstone Arsenal, AL 11R. E. Turner et al, 1978, Model Development for E-O

  10. The USRA workshop report: Electrostatic fog dispersal

    NASA Technical Reports Server (NTRS)

    Davis, M. H. (Editor)

    1983-01-01

    The Workshop was held at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, on February 1-2, 1983. The Workshop was attended by seventeen experts in the scientific fields of fog and cloud physics, charged-particle electrodynamics, atmospheric turbulence, atmospheric electricity, and electro-gasdynamics. The major objective of the Workshop was to assess the scientific merits and scientific basis of the proposed system and to assess its potential for operational application.

  11. High repetition rate ultrashort laser cuts a path through fog

    NASA Astrophysics Data System (ADS)

    de la Cruz, Lorena; Schubert, Elise; Mongin, Denis; Klingebiel, Sandro; Schultze, Marcel; Metzger, Thomas; Michel, Knut; Kasparian, Jérôme; Wolf, Jean-Pierre

    2016-12-01

    We experimentally demonstrate that the transmission of a 1030 nm, 1.3 ps laser beam of 100 mJ energy through fog increases when its repetition rate increases to the kHz range. Due to the efficient energy deposition by the laser filaments in the air, a shockwave ejects the fog droplets from a substantial volume of the beam, at a moderate energy cost. This process opens prospects for applications requiring the transmission of laser beams through fogs and clouds.

  12. Msg Fog and Low Stratus Products at Lcrs (sofos)

    NASA Astrophysics Data System (ADS)

    Cermak, J.; Bendix, J.; Nauß, T.

    2006-08-01

    This paper presents the Satellite-based Operational Fog Observation Scheme (SOFOS) developed at the Laboratory for Climatology and Remote Sensing (LCRS), University of Marburg, Germany, based on Meteosat 8 SEVIRI data. The scheme currently consists of four components: Daytime very low stratus detection, daytime ground fog delineation, fog dissipation modelling and nighttime low stratus detection. Each of these is briefly introduced in the following

  13. Characterization of polycyclic aromatic hydrocarbons in fog-rain events.

    PubMed

    Li, Xiang; Li, Pengfei; Yan, Lili; Chen, Jianmin; Cheng, Tiantao; Xu, Shifen

    2011-11-01

    Atmospheric polycyclic aromatic hydrocarbons (PAHs) mainly originate from incomplete combustion or pyrolysis of materials containing carbon and hydrogen. They exist in gas and particle phases, as well as dissolved or suspended in precipitation (fog or rain). Current studies in atmospheric PAHs are predominantly focused on fog and rainwater samples. Some sampling difficulties are associated with fog samples. This study presented the first observation of the characteristics of PAHs in fog samples using a solid phase microextraction (SPME) technique. Eighteen fog samples were collected during ten fog events from March to December 2009 in the Shanghai area. PAHs were extracted by SPME and analyzed by gas chromatography-mass spectrometry (GC-MS). As the compounds were partially soluble in water, with solubility decreasing with increasing molecular weight, low molecular weight (LMW) PAH compounds were universally found in the fog water samples. Naphthalene (NaP), phenanthrene (Phe), anthracene (Ant) and fluoranthene (Flo) were dominant compounds in fog water. The total PAH concentration in fog water ranged from 0.03 to 6.67 μg L(-1) (mean of 1.06 μg L(-1)), and was much higher in winter than in summer. The concentration of PAHs in fog or rain water decreased after undergoing a pre-rain or pre-fog wash. The average concentration of PAHs was higher in fog than in rain. Diagnostic ratio analysis suggested that petroleum and combustion were the dominant contributors to PAHs in urban Shanghai. Backward trajectories were calculated to determine the origin of the air masses, showing that air masses were mostly from the northeast territory.

  14. Animal or Plant: Which Is the Better Fog Water Collector?

    PubMed Central

    Nørgaard, Thomas; Ebner, Martin; Dacke, Marie

    2012-01-01

    Occasional fog is a critical water source utilised by plants and animals in the Namib Desert. Fog basking beetles (Onymacris unguicularis, Tenebrionidae) and Namib dune bushman grass (Stipagrostris sabulicola, Poaceae) collect water directly from the fog. While the beetles position themselves optimally for fog water collection on dune ridges, the grass occurs predominantly at the dune base where less fog water is available. Differences in the fog-water collecting abilities in animals and plants have never been addressed. Here we place beetles and grass side-by-side in a fog chamber and measure the amount of water they collect over time. Based on the accumulated amount of water over a two hour period, grass is the better fog collector. However, in contrast to the episodic cascading water run-off from the grass, the beetles obtain water in a steady flow from their elytra. This steady trickle from the beetles' elytra to their mouth could ensure that even short periods of fog basking – while exposed to predators – will yield water. Up to now there is no indication of specialised surface properties on the grass leafs, but the steady run-off from the beetles could point to specific property adaptations of their elytra surface. PMID:22509331

  15. Efficient fog harvesting by Stipagrostis sabulicola (Namib dune bushman grass)

    NASA Astrophysics Data System (ADS)

    Roth-Nebelsick, A.; Ebner, M.; Miranda, T.

    2010-07-01

    Stipagrostis sabulicola is an endemic species of the central Namib Desert which settles on extremely arid dune fields. Due to its ability to persistence even during exceptionally dry years it is generally assumed that water supply of this species is substantially based on fog water. In this contribution, the results of a study investigating the capability of S. sabulicola for fog harvesting are presented. For this purpose, stem flow rates of S. sabulicola during fog events, spatial gradient of soil water content (SWC) close to mounds of S. sabulicola and its leaf water potential (LWP) before and after fog events were monitored together with climate parameters. According to the data obtained during this study, S. sabulicola is able to harvest substantial amounts of water by fog catchment from nocturnal fog events. Since culms of S. sabulicola are often stiff with an upright habitus, fog harvesting occurs via stemflow that conducts water directly towards the root zone of a plant. According to this mechanism, the stem runoff is concentrated within the area of the mound. A medium-sized mound of S. sabulicola is able to collect an amount of about 4 l per fog night. This fog harvesting leads to a considerable spatial gradient of soil water content with values decreasing with increasing distance from the mound. As a result of the water input by fog drip, SWC within the mound increases significantly, particularly close to the culm bases where SWC values increased to 2.2 % after a fog event. Due to the uneven distribution of water by stemflow, SWC within a mound shows high spatial heterogeneity which is also illustrated by the numerous outliers and extreme values of SWC within the mound region. This heterogeneity is also due to the fact that several sagging leaves are always present causing fog drip which more or less irregularly scatters moisture. For bare soil outside of a mound, the water content is not substantially increased, amounting to 0.78 % on average during dry

  16. Animal or plant: which is the better fog water collector?

    PubMed

    Nørgaard, Thomas; Ebner, Martin; Dacke, Marie

    2012-01-01

    Occasional fog is a critical water source utilised by plants and animals in the Namib Desert. Fog basking beetles (Onymacris unguicularis, Tenebrionidae) and Namib dune bushman grass (Stipagrostris sabulicola, Poaceae) collect water directly from the fog. While the beetles position themselves optimally for fog water collection on dune ridges, the grass occurs predominantly at the dune base where less fog water is available. Differences in the fog-water collecting abilities in animals and plants have never been addressed. Here we place beetles and grass side-by-side in a fog chamber and measure the amount of water they collect over time. Based on the accumulated amount of water over a two hour period, grass is the better fog collector. However, in contrast to the episodic cascading water run-off from the grass, the beetles obtain water in a steady flow from their elytra. This steady trickle from the beetles' elytra to their mouth could ensure that even short periods of fog basking--while exposed to predators--will yield water. Up to now there is no indication of specialised surface properties on the grass leafs, but the steady run-off from the beetles could point to specific property adaptations of their elytra surface.

  17. Small-scale particle advection, manipulation and mixing: beyond the hydrodynamic scale.

    PubMed

    Straube, Arthur V

    2011-05-11

    In this paper we discuss the problems of particle advection, manipulation and mixing at small scales. We start by considering reaction-advection-diffusion systems with the focus on mixing. We show how mixing advection affects the processes of reaction-diffusion and discuss mixing-induced instabilities. Further, we consider the problem of particle manipulation and discuss collective effects in systems comprising solid and compressible particles. We particularly discuss mechanisms of particle entrapment, the role of compressibility in the dynamics of bubbly liquids and nonequilibrium colloidal explosion. Finally, we address two issues related to the problem of wetting. First, we study the role of contact line motion for a sessile droplet (or a bubble) on an oscillating substrate. Second, we discuss an instability of a thin film leading to the formation of a fractal structure of droplets.

  18. Study of fog characteristics by using the 1-D COBEL model at the airport of Thessaloniki, Greece

    NASA Astrophysics Data System (ADS)

    Stolaki, S.; Pytharoulis, I.; Karacostas, T.

    2010-07-01

    An attempt is made to couple the one dimensional COBEL - ISBA (COuche Brouillard Eau Liquide - Interactions Soil Biosphere Atmosphere) model with the WRF (Weather Research and Forecasting) numerical weather prediction model. This accomplishment will improve the accuracy on the short-term forecasting of fog events, which is of paramount importance -mainly to the airway companies, the airports functioning and the community as well- and will provide the means for the implementation of extensive studies of fog events formed at the "Macedonia" airport of Thessaloniki. Numerical experiments have been performed to study in depth the thermodynamic structure and the microphysical characteristics of the fog event that was formed on 06/01/2010. Moreover, the meteorological conditions -under the influence of which- the fog event was formed are also investigated. Sensitivity tests with respect to the initial conditions of temperature, relative humidity and geostrophic wind speed profiles have been performed to illustrate the model’s performance. Dew deposition rates have also been examined in order to test the importance of it on controlling the fog formation. The numerical results have been compared with actual measurements and the findings have been evaluated and discussed.

  19. SO/sub 2/(g)-to-sulfate conversion rate in an oil-fired-power-plant plume in a fog bank

    SciTech Connect

    Eatough, D.J.; Arthur, R.J.; Eatough, N.L.; Hill, M.W.; Mangelson, N.F.; Richter, B.E.; Hansen, L.D.; Cooper, J.A.

    1983-01-01

    High acidity in rainfall, cloud droplets and fog droplets in areas influenced by anthropogenic sources of SO/sub 2/(g) and NO/sub x/(g) has been attributed to the formation of both H/sub 2/SO/sub 4/ and HNO/sub 3/. It has been suggested, based on the analysis of field data, that rapid conversion of SO/sub 2/(g) to sulfate must occur in cloud or fog droplets. Direct measurements of the rate of SO/sub 2/(g) to sulfate conversion in an oil-fired power plant plume as it passes through a fog bank are reported here. A conversion rate of 30+-4% SO/sub 2/(g) h/sup -1/ was found in the fog bank.

  20. Microscale chaotic advection enables robust convective DNA replication.

    PubMed

    Priye, Aashish; Hassan, Yassin A; Ugaz, Victor M

    2013-11-05

    The ability of chaotic advection under microscale confinement to direct chemical processes along accelerated kinetic pathways has been recognized for some time. However, practical applications have been slow to emerge because optimal results are often counterintuitively achieved in flows that appear to possess undesirably high disorder. Here we present a 3D time-resolved analysis of polymerase chain reaction (PCR)-mediated DNA replication across a broad ensemble of geometric states. The resulting parametric map reveals an unexpectedly wide operating regime where reaction rates remain constant over 2 orders of magnitude of the Rayleigh number, encompassing virtually any realistic PCR condition (temperature, volume, gravitational alignment), a level of robustness previously thought unattainable in the convective format.

  1. A computational method for sharp interface advection

    PubMed Central

    Bredmose, Henrik; Jasak, Hrvoje

    2016-01-01

    We devise a numerical method for passive advection of a surface, such as the interface between two incompressible fluids, across a computational mesh. The method is called isoAdvector, and is developed for general meshes consisting of arbitrary polyhedral cells. The algorithm is based on the volume of fluid (VOF) idea of calculating the volume of one of the fluids transported across the mesh faces during a time step. The novelty of the isoAdvector concept consists of two parts. First, we exploit an isosurface concept for modelling the interface inside cells in a geometric surface reconstruction step. Second, from the reconstructed surface, we model the motion of the face–interface intersection line for a general polygonal face to obtain the time evolution within a time step of the submerged face area. Integrating this submerged area over the time step leads to an accurate estimate for the total volume of fluid transported across the face. The method was tested on simple two-dimensional and three-dimensional interface advection problems on both structured and unstructured meshes. The results are very satisfactory in terms of volume conservation, boundedness, surface sharpness and efficiency. The isoAdvector method was implemented as an OpenFOAM® extension and is published as open source. PMID:28018619

  2. Striated populations in disordered environments with advection

    NASA Astrophysics Data System (ADS)

    Chotibut, Thiparat; Nelson, David R.; Succi, Sauro

    2017-01-01

    Growth in static and controlled environments such as a Petri dish can be used to study the spatial population dynamics of microorganisms. However, natural populations such as marine microbes experience fluid advection and often grow up in heterogeneous environments. We investigate a generalized Fisher-Kolmogorov-Petrovsky-Piscounov (FKPP) equation describing single species population subject to a constant flow field and quenched random spatially inhomogeneous growth rates with a fertile overall growth condition. We analytically and numerically demonstrate that the non-equilibrium steady-state population density develops a flow-driven striation pattern. The striations are highly asymmetric with a longitudinal correlation length that diverges linearly with the flow speed and a transverse correlation length that approaches a finite velocity-independent value. Linear response theory is developed to study the statistics of the steady states. Theoretical predictions show excellent agreement with the numerical steady states of the generalized FKPP equation obtained from Lattice Boltzmann simulations. These findings suggest that, although the growth disorder can be spatially uncorrelated, correlated population structures with striations emerge naturally at sufficiently strong advection.

  3. Waves, advection, and cloud patterns on Venus

    NASA Technical Reports Server (NTRS)

    Schinder, Paul J.; Gierasch, Peter J.; Leroy, Stephen S.; Smith, Michael D.

    1990-01-01

    The stable layers adjacent to the nearly neutral layer within the Venus clouds are found to be capable of supporting vertically trapped, horizontally propagating waves with horizontal wavelengths of about 10 km and speeds of a few meters per second relative to the mean wind in the neutral layer. These waves may possibly be excited by turbulence within the neutral layer. Here, the properties of the waves, and the patterns which they might produce within the visible clouds if excited near the subsolar point are examined. The patterns can be in agreement with many features in images. The waves are capable of transferring momentum latitudinally to help maintain the general atmospheric spin, but at present we are not able to evaluate wave amplitudes. We also examine an alternative possibility that the cloud patterns are produced by advection and shearing by the mean zonal and meridional flow of blobs formed near the equator. It is concluded that advection and shearing by the mean flow is the most likely explanation for the general pattern of small scale striations.

  4. Parallel algorithms for semi-lagrangian advection

    NASA Astrophysics Data System (ADS)

    Malevsky, A. V.; Thomas, S. J.

    1997-08-01

    Numerical time step limitations associated with the explicit treatment of advection-dominated problems in computational fluid dynamics are often relaxed by employing Eulerian-Lagrangian methods. These are also known as semi-Lagrangian methods in the atmospheric sciences. Such methods involve backward time integration of a characteristic equation to find the departure point of a fluid particle arriving at a Eulerian grid point. The value of the advected field at the departure point is obtained by interpolation. Both the trajectory integration and repeated interpolation influence accuracy. We compare the accuracy and performance of interpolation schemes based on piecewise cubic polynomials and cubic B-splines in the context of a distributed memory, parallel computing environment. The computational cost and interprocessor communication requirements for both methods are reported. Spline interpolation has better conservation properties but requires the solution of a global linear system, initially appearing to hinder a distributed memory implementation. The proposed parallel algorithm for multidimensional spline interpolation has almost the same communication overhead as local piecewise polynomial interpolation. We also compare various techniques for tracking trajectories given different values for the Courant number. Large Courant numbers require a high-order ODE solver involving multiple interpolations of the velocity field.

  5. O'Neill's Kurzdrama "Fog" im Englischunterricht (O'Neill's Short Drama "Fog" in English Teaching)

    ERIC Educational Resources Information Center

    Wolter, Juergen

    1977-01-01

    O'Neill's "Fog" is recommended as a discussion-stimulating work for English (as a second language) classes in grades 11-13. The content is discussed from an instructional point of view. Teaching goals are considered. Experiences with the play in grade 11 are described, and methodological hints are given. (Text is in German.) (IFS/WGA)

  6. Fog chemical composition and its feedback to fog water fluxes, water vapor fluxes, and microphysical evolution of two events near Paris

    NASA Astrophysics Data System (ADS)

    Degefie, D. T.; El-Madany, T.-S.; Held, M.; Hejkal, J.; Hammer, E.; Dupont, J.-C.; Haeffelin, M.; Fleischer, E.; Klemm, O.

    2015-10-01

    The chemical composition of collected fog water and its temporal evolution was studied during the PARISFOG campaign in winter 2012/2013 at the SIRTA (Site Instrumental de Recherche par Télédétection Atmosphéric) atmospheric observatory outside Paris, France. A further development of the caltech active fog collector was applied, in which the collected fog water gets into contact with Teflon and polyether ether ketone (PEEK) material exclusively. The collector was operational whenever the visibility was below 1000 m. In addition, the turbulent and gravitational fluxes of fog water and water vapor flux were used to examine in detail the temporal evolution the chemical composition of two fogs. The technique was applied to two fog events, one representing a radiation fog and the other one representing a stratus lowering fog. The result revealed that the dominant inorganic species in the fog water were NH4+, NO3-, Ca2 + and SO42 -, which accounted for more than 85% of the ion balance. The pH ranged from 3.7 to 6.2. In the evolution the two fog events, the interaction among the turbulent fog water flux, gravitational fog water flux and water vapor flux controlled the major ion loads (amount of ions, dissolved in fog droplets per volume of air) and ion concentrations (amount dissolved per volume of liquid water) of the fog water. In the radiation fog event, an increase of ion loads and ion concentrations occurred when the direction of water vapor flux towards to the place where the condensation process occurred. A decrease of ion loads and ion concentrations mainly happened by gravitational fog water flux with a minor contribution from turbulent fog water flux. However, when the turbulent water vapor flux was oriented downward, it turned the turbulent fog water flux upward and offset the removal of ions in the fog. In the stratus lowering fog event, the turbulent fog water flux and the gravitational water flux together mainly contributed to the fog water deposition and

  7. Detection of Fog/Low Stratus Using MSG SEVIRI Images

    NASA Astrophysics Data System (ADS)

    Erturk, A. G.; Prieto, J.

    2010-07-01

    In winter condition, fog is severely affecting air, sea and land transportation. Automatically detection of fog and low stratus using satellite data is one of the crucial implementation of operational nowcasting system. High temporal and spectral bands of MSG SEVIRI support to the operational nowcasting application in the large scale coverage. Small-droplet emissivities are different at 10.8 and 3.9 micron bands, and Brightness Temperature Differences (BTD) between Channel 3.9 and Channel 10.8 can be efficiently employed to detect fog/low stratus. Additionally the RGB composite image (called "fog RGB") derived from BTD of Channel 12.0 and Channel10.8, BTD of Channel 3.9 and Channel 10.8 and BT of Channel 10.8 is another useful tool to recognize fog in night time. Occasionally, in particular at high latitudes on frozen grounds, the use of 8.7µm instead of 3.9 µm proves beneficial. In this study, MSG SEVIRI applications will be presented to detect fog and low stratus. Additionally, catastrophic fog event occurred at 20-26 November 2009 over western Turkey will be presented. Satellite based fog detection gives more opportunities to forecasters in very short term prediction.

  8. Multidecadal simulation of coastal fog with a regional climate model

    NASA Astrophysics Data System (ADS)

    O'Brien, Travis A.; Sloan, Lisa C.; Chuang, Patrick Y.; Faloona, Ian C.; Johnstone, James A.

    2013-06-01

    In order to model stratocumulus clouds and coastal fog, we have coupled the University of Washington boundary layer model to the regional climate model, RegCM (RegCM-UW). By comparing fog occurrences observed at various coastal airports in the western United States, we show that RegCM-UW has success at modeling the spatial and temporal (diurnal, seasonal, and interannual) climatology of northern California coastal fog. The quality of the modeled fog estimate depends on whether coast-adjacent ocean or land grid cells are used; for the model runs shown here, the oceanic grid cells seem to be most appropriate. The interannual variability of oceanic northern California summertime fog, from a multi-decadal simulation, has a high and statistically significant correlation with the observed interannual variability ( r = 0.72), which indicates that RegCM-UW is capable of investigating the response of fog to long-term climatological forcing. While RegCM-UW has a number of aspects that would benefit from further investigation and development, RegCM-UW is a new tool for investigating the climatology of coastal fog and the physical processes that govern it. We expect that with appropriate physical parameterizations and moderate horizontal resolution, other climate models should be capable of simulating coastal fog. The source code for RegCM-UW is publicly available, under the GNU license, through the International Centre for Theoretical Physics.

  9. 12. Fuel house and fog signal house, view northeast, southwest ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. Fuel house and fog signal house, view northeast, southwest side of fuel house, west and south sides of fog signal house - Cape Elizabeth Light Station, Near Two Lights State Park at end of Two Lights Road, off State Highway 77, Cape Elizabeth, Cumberland County, ME

  10. 7. Keeper's house, fog signal house and light tower, view ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. Keeper's house, fog signal house and light tower, view north northeast, west and south sides of keeper's house and tower, southwest and southeast sides of fog signal house - West Quoddy Head Light Station, At eastern tip of West Quaddy Head, Lubec, Washington County, ME

  11. Clearing the Fog from the Undergraduate Course in Linear Algebra

    ERIC Educational Resources Information Center

    Scott, Damon

    2007-01-01

    For over a decade it has been a common observation that a "fog" passes over the course in linear algebra once abstract vector spaces are presented. See [2, 3]. We show how this fog may be cleared by having the students translate "abstract" vector-space problems to isomorphic "concrete" settings, solve the "concrete" problem either by hand or with…

  12. Fog, Clouds and the Maintenance of Ecosystems: Mist Opportunities?

    NASA Astrophysics Data System (ADS)

    Weathers, K. C.

    2006-12-01

    What is the significance of occult precipitation-- otherwise known as fog or cloud water (terms used interchangeably here)--in the maintenance of ecosystems? More than a century of natural history observations and decades of research have demonstrated that occult precipitation does deliver water, nutrients, and pollutants to coastal and montane ecosystems, but that its ecological importance is likely to vary by ecosystem. Still, many key ecological questions about the role of fog in the maintenance of ecosystems remain unanswered: For example, what is the effect of fog water and nutrient inputs on annual productivity or rates of nutrient cycling? Are soil processes affected by fog water input to ecosystems? To what extent do plants or animals actually use cloud or fog-delivered nutrients, and if they do, what are the mechanisms? Does fog input control the distribution and abundance of plant and/or animal species? If so, are the mechanisms hydrologic, physical (i.e., influence on temperature or light) and/or nutrient based? Although many of the early observations and research suggested that the delivery of water was one of the more important roles of fog in ecosystem maintenance, we and others have demonstrated that nutrient, as well as pollutants in fog are often 3-10x more concentrated than rain water, and can range up to 100x more concentrated. In some ecosystems, such as old growth forests on Chiloe Island, Chile, we have shown that comparatively large nutrient (e.g., nitrogen) loads can be delivered to ecosystems via a small amount (10s of cms/year) of fog water deposition. Thus, a little fog water has the potential to influence ecosystem processes. In addition, we have hypothesized that "the ocean may be feeding the forest," i.e., the source of the nutrients in fog water may be the ocean. In contrast to this fog subsidy, the ecological function of some high-elevation forests in the northeastern United States has been shown to be negatively impacted, in part

  13. Characterization of organic residues of size-resolved fog droplets and their atmospheric implications

    NASA Astrophysics Data System (ADS)

    Chakraborty, Abhishek; Ervens, Barbara; Gupta, Tarun; Tripathi, Sachchida N.

    2016-04-01

    Size-resolved fog water samples were collected in two consecutive winters at Kanpur, a heavily polluted urban area of India. Samples were analyzed by an aerosol mass spectrometer after drying and directly in other instruments. Residues of fine fog droplets (diameter: 4-16 µm) are found to be more enriched with oxidized (oxygen to carbon ratio, O/C = 0.88) and low volatility organics than residues of coarse (diameter > 22 µm) and medium size (diameter: 16-22 µm) droplets with O/C of 0.68 and 0.74, respectively. These O/C ratios are much higher than those observed for background ambient organic aerosols, indicating efficient oxidation in fog water. Accompanying box model simulations reveal that longer residence times, together with high aqueous OH concentrations in fine droplets, can explain these trends. High aqueous OH concentrations in smaller droplets are caused by their highest surface-volume ratio and high Fe and Cu concentrations, allowing more uptake of gas phase OH and enhanced Fenton reaction rates, respectively. Although some volatile organic species may have escaped during droplet evaporation, these findings indicate that aqueous processing of dissolved organics varies with droplet size. Therefore, large (regional, global)-scale models need to consider the variable reaction rates, together with metal-catalyzed radical formation throughout droplet populations for accurately predicting aqueous secondary organic aerosol formation.

  14. Large volume water sprays for dispersing warm fogs

    NASA Astrophysics Data System (ADS)

    Keller, V. W.; Anderson, B. J.; Burns, R. A.; Lala, G. G.; Meyer, M. B.

    A new method for dispersing of warm fogs which impede visibility and alter schedules is described. The method uses large volume recycled water sprays to create curtains of falling drops through which the fog is processed by the ambient wind and spray-induced air flow; the fog droplets are removed by coalescence/rainout. The efficiency of this fog droplet removal process depends on the size spectra of the spray drops and optimum spray drop size is calculated as between 0.3-1.0 mm in diameter. Water spray tests were conducted in order to determine the drop size spectra and temperature response of sprays produced by commercially available fire-fighting nozzles, and nozzle array tests were utilized to study air flow patterns and the thermal properties of the overall system. The initial test data reveal that the fog-dispersal procedure is effective.

  15. BUOYANT ADVECTION OF GASES IN UNSATURATED SOIL

    PubMed Central

    Seely, Gregory E.; Falta, Ronald W.; Hunt, James R.

    2010-01-01

    In unsaturated soil, methane and volatile organic compounds can significantly alter the density of soil gas and induce buoyant gas flow. A series of laboratory experiments was conducted in a two-dimensional, homogeneous sand pack with gas permeabilities ranging from 110 to 3,000 darcy. Pure methane gas was injected horizontally into the sand and steady-state methane profiles were measured. Experimental results are in close agreement with a numerical model that represents the advective and diffusive components of methane transport. Comparison of simulations with and without gravitational acceleration permits identification of conditions where buoyancy dominates methane transport. Significant buoyant flow requires a Rayleigh number greater than 10 and an injected gas velocity sufficient to overcome dilution by molecular diffusion near the source. These criteria allow the extension of laboratory results to idealized field conditions for methane as well as denser-than-air vapors produced by volatilizing nonaqueous phase liquids trapped in unsaturated soil. PMID:20396624

  16. Measurements of Cloud Droplet Size and Fog Water Deposition

    NASA Astrophysics Data System (ADS)

    Fernandez, D.; Lee, T.; Torregrosa, A.; Underwood, J.; Andersen, D.

    2013-12-01

    The size of cloud droplets is a factor in the variability of coastal low clouds and fog. The relationship between cloud droplet size and volume of fog water collected as a function of position over land may provide useful information for fog related mechanisms such as water deposition via fog drip, aerosol scavenging, and cloud top radiation flux. We derive landscape-level estimates of cloud top droplet size through the application of a three channel-based algorithm on geostationary operational environmental satellite (GOES) data. The result retrieves cloud top droplet size, cloud top temperature, cloud optical depth, emissivity, and cloud top height. Comparable information on droplet size has been used for years in ocean experiments accompanied by observations from ships and aircraft, but it has not been explored for use in coastal environments. Retrievals are still experimental and are confined to daytime hours of about 1000 - 1600 hours local time. We are exploring the use of cloud-top GOES derived droplet size data to better understand fog water deposition along the central California coast through comparative analysis with 1) ground-based volumetric fog water data collected from several 1.00 square meter fog collectors deployed in Marina, CA and active fog water samplers inland at Pepperwood Preserve ; 2) droplet size distributions (between 2 - 50 μm) sampled with an optical spectrometer along a coast to inland transect, and 3) trajectory swaths from the three cloud-aerosol LIDAR instrument system (CALIPSO) coincident in location with #1 and #2. Satellite-derived coastal drop size data show large droplet size at the coast and smaller droplet sizes inland. The data observed may provide information on the relationship between the fog droplet diameter and the volume of fog water collected as a function of location from the coast.

  17. UAV applications for thermodynamic profiling: Emphasis on ice fog research

    NASA Astrophysics Data System (ADS)

    Gultepe, Ismail; Heymsfield, Andrew J.; Fernando, Harindra J. S.; Hoch, Sebastian W.; Ware, Randolph

    2016-04-01

    Ice fog occurs often over the Arctic, cold climatic, and mountainous regions for about 30% of time where temperature (T) can go down to -10°C or below. Ice Nucleation (IN) and cooling processes play an important role by the controlling the intensity of ice fog conditions that affect aviation application, transportation, and local climate. Ice fog can also occur at T above -10°C but close to 0°C it occurs due to freezing of supercooled droplets that include an IN. To better document ice fog conditions, observations from the ice fog events of the Indirect and Semi-Direct Aerosol effects on Climate (ISDAC) project, Barrow, Alaska, Fog Remote Sensing And Modeling (FRAM) project Yellowknife, Northwest Territories, and the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) project, Heber City, Utah, were analyzed.. Measurements difficulties of small ice fog particles at cold temperatures and low-level flying restrictions prevent observations from aircraft within the surface boundary layer. However, unmanned Aerial Vehicles (UAVs) can be operated safely to measure IN number concentration, Relative Humidity with respect to ice (RHi), T, horizontal wind speed (Uh) and direction, and ice crystal spectra less than about 500 micron. Thermodynamic profiling by a Radiometrics Profiling Microwave Radiometer (PMWR) and Vaisala CL51 ceilometer was used to describe ice fog conditions in the vertical and its time development. In this presentation, ice fog characteristics and its thermodynamic environment will be presented using both ground-based and airborne platforms such as a UAV with new sensors. Some examples of measurements from the UAV for future research, and challenges related to both ice fog measurements and visibility parameterization will also be presented.

  18. Exploring microphysical, radiative, dynamic and thermodynamic processes driving fog and low stratus clouds using ground-based Lidar and Radar measurements

    NASA Astrophysics Data System (ADS)

    Haeffelin, Martial

    2016-04-01

    Radiation fog formation is largely influenced by the chemical composition, size and number concentration of cloud condensation nuclei and by heating/cooling and drying/moistening processes in a shallow mixing layer near the surface. Once a fog water layer is formed, its development and dissipation become predominantly controlled by radiative cooling/heating, turbulent mixing, sedimentation and deposition. Key processes occur in the atmospheric surface layer, directly in contact with the soil and vegetation, and throughout the atmospheric column. Recent publications provide detailed descriptions of these processes for idealized cases using very high-resolution models and proper representation of microphysical processes. Studying these processes in real fog situations require atmospheric profiling capabilities to monitor the temporal evolution of key parameters at several heights (surface, inside the fog, fog top, free troposphere). This could be done with in-situ sensors flown on tethered balloons or drones, during dedicated intensive field campaigns. In addition Backscatter Lidars, Doppler Lidars, Microwave Radiometers and Cloud Doppler Radars can provide more continuous, yet precise monitoring of key parameters throughout the fog life cycle. The presentation will describe how Backscatter Lidars can be used to study the height and kinetics of aerosol activation into fog droplets. Next we will show the potential of Cloud Doppler Radar measurements to characterize the temporal evolution of droplet size, liquid water content, sedimentation and deposition. Contributions from Doppler Lidars and Microwave Radiometers will be discussed. This presentation will conclude on the potential to use Lidar and Radar remote sensing measurements to support operational fog nowcasting.

  19. Non-Linearity Explanation in Artificial Neural Network Application with a Case Study of Fog Forecast Over Delhi Region

    NASA Astrophysics Data System (ADS)

    Saurabh, K.; Dimri, A. P.

    2016-05-01

    Fog affects human life in a number of ways by reducing the visibility, hence affecting critical infrastructure, transportation, tourism or by the formation of frost, thus harming the standing crops. Smog is becoming a regular phenomenon in urban areas which is highly toxic to humans. Delhi was chosen as the area of study as it encounters all these hazards of fog stated apart from other political and economic reasons. The complex relationship behind the parameters and processes behind the formation of fog makes it extremely difficult to model and forecast it accurately. It is attempted to forecast the fog and understand its dynamics through a statistical downscaling technique of artificial neural network which is deemed accurate for short-term forecasting and usually outperform time-series models. The backpropagation neural network, which is a gradient descent algorithm where the network weights are moved along the negative of the gradient of the performance function, has been used for our analysis. Indian Meteorological Department (IMD) supported National Oceanic and Atmospheric Administration (NOAA) data had been used for carrying out the simulations. The model was found to have high accuracy but lacking in skill. An attempt has been made to present the data in a binary form by determining a threshold by the contingency table approach followed by its critical analysis. It is found that the calculation of an optimum threshold was also difficult to fix as the parameters of fog formation on which the model has been has been trained had shown some changes in their trend over a period of time.

  20. Daily lifestyles in the fog and haze weather

    PubMed Central

    Cai, Dong-Ping

    2016-01-01

    Background China is being plagued by a large-scaled lasting fog and haze, under which people have to work and live. Therefore, it matters to do what we can to minimize the adverse impact of the fog and haze on individual health on a daily basis. Methods Relative literatures on the fog and haze have been searched and reviewed. Particular attention has been paid to the literatures on the adverse impact of the fog and haze on the people’s health and on the ways minimizing this impact. Results Coming across the weather of fog and haze, appropriate measures taken can minimize its adverse impact on individuals on a daily basis. The measures included vitamin intake, water drinking, air cleaning indoors, stay-at-home, and mask wearing outdoors. These measures are simple and proven effective. Conclusions Simple and effective measures seem to be sufficient to minimizing the adverse impact of the fog and haze on the individual’s health on a daily basis. Lifestyle changes, awareness of environment protection, energy conservation, and new and clean energy use are ultimate ways to curb the air pollution and reduce the occurrence of the fog and haze. PMID:26904256

  1. Foliar uptake of fog in coastal California shrub species.

    PubMed

    Emery, Nathan C

    2016-11-01

    Understanding plant water uptake is important in ecosystems that experience periodic drought. In many Mediterranean-type climates like coastal California, plants are subject to significant drought and wildfire disturbance. During the dry summer months, coastal shrub species are often exposed to leaf wetting from overnight fog events. This study sought to determine whether foliar uptake of fog occurs in shrub species and how this uptake affects physiology and fuel condition. In a controlled greenhouse experiment, dominant California shrub species were exposed to isotopically labeled fog water and plant responses were measured. Potted plants were covered at the base to prevent root uptake. The deuterium label was detected in the leaves of four out of five species and in the stems of two of the species. While there was a minimal effect of foliar water uptake on live fuel moisture, several species had lower xylem tension and greater photosynthetic rates after overnight fog treatments, especially Salvia leucophylla. Coastal fog may provide a moisture source for many species during the summer drought, but the utilization of this water source may vary based on foliar morphology, phenology and plant water balance. From this study, it appears that drought-deciduous species (Artemisia californica and Salvia leucophylla) benefit more from overnight fog events than evergreen species (Adenostoma fasciculatum, Baccharis pilularis and Ceanothus megacarpus). This differential response to fog exposure among California shrub species may affect species distributions and physiological tolerances under future climate scenarios.

  2. Optimal design of permeable fiber network structures for fog harvesting.

    PubMed

    Park, Kyoo-Chul; Chhatre, Shreerang S; Srinivasan, Siddarth; Cohen, Robert E; McKinley, Gareth H

    2013-10-29

    Fog represents a large untapped source of potable water, especially in arid climates. Numerous plants and animals use textural and chemical features on their surfaces to harvest this precious resource. In this work, we investigate the influence of the surface wettability characteristics, length scale, and weave density on the fog-harvesting capability of woven meshes. We develop a combined hydrodynamic and surface wettability model to predict the overall fog-collection efficiency of the meshes and cast the findings in the form of a design chart. Two limiting surface wettability constraints govern the re-entrainment of collected droplets and clogging of mesh openings. Appropriate tuning of the wetting characteristics of the surfaces, reducing the wire radii, and optimizing the wire spacing all lead to more efficient fog collection. We use a family of coated meshes with a directed stream of fog droplets to simulate a natural foggy environment and demonstrate a five-fold enhancement in the fog-collecting efficiency of a conventional polyolefin mesh. The design rules developed in this work can be applied to select a mesh surface with optimal topography and wetting characteristics to harvest enhanced water fluxes over a wide range of natural convected fog environments.

  3. Simulating Coastal Fog with a Regional Climate Model

    NASA Astrophysics Data System (ADS)

    O'Brien, T. A.; Sloan, L. C.; Chuang, P. Y.; Faloona, I. C.; Rossiter, D. L.

    2011-12-01

    We introduce a new tool for studying the physical processes that control coastal fog. We have coupled the University of Washington (UW) boundary layer model to the International Centre for Theoretical Physics's regional climate model, RegCM v4.0. The UW model explicitly includes physical processes relevant to stratocumulus clouds and coastal fog. The coupling of the UW model to RegCM (RegCM-UW) adds marine stratocumulus clouds (MSc) to RegCM; the modeled MSc compare well with observations of MSc at a variety of temporal scales (from synoptic to decadal). In accord with observations of MSc, the height of the modeled cloud deck (base and top) decreases approaching the coast, such that the MSc are frequently below the 400 m altitude threshold that Johnstone and Dawson (2010) use as a definition of fog. The spatial and temporal variability of modeled coastal fog is generally in accord with the observed spatiotemporal variability. In addition to the good agreement between the modeled interannual variability of northern California coastal fog, the model hindcasts a long-term decline in northern California coastal fog frequency that is statistically significant and statistically indistinguishable from the observed decline. Sensitivity tests show that the modeled coastal fog frequency is controlled strongly by sea surface temperature (SST) in a manner consistent with the Bakun hypothesis; cooler SSTs lead to higher fog frequency and vice-versa. We discuss research-in-progress that aims to elucidate how and why fog has declined in the recent past and how it may change in the future.

  4. Coastal Upwelling and Deep Fog: 50-year Worldwide Climatology

    NASA Astrophysics Data System (ADS)

    Koracin, D. R.

    2015-12-01

    An analysis is presented of the marine fog distribution based upon the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) ship observations taken during 1950-2007. Deep fog occurrence is reported in routine weather reports that are encoded in an ICOADS ship observation. Occurrence is estimated by the number of deep fog observations divided by the total present weather observations in a one-degree area centered on latitude and longitude grid point intersections. The mean fog occurrence for the summer (June-July-August) 1950-2007 was computed for each one degree point for the world. There are five major world locations with coastal SST minimums due to wind driven upwelling. Four of these are during the local summer on the eastern side of a semi-permanent anticyclone on eastern sides of northern and southern mid-latitudes of the Pacifica and the Atlantic. The fifth is during the SW monsoon in the Indian Ocean. For all five of these locations, the deep fog occurrence is at maximum during the upwelling season, with the greatest occurrences concentrated along the coast and isolated over the SST minimum. For the five coastal fog maxima, the greatest and longest duration occurrence along coast occurrence is associated with the coldest sea surface temperature and longest along coast occurrence, which is along N. California- S. Oregon. In contrast, the lowest occurrence of fog and the least along coast occurrence is associated with the warmest sea surface temperatures and least along coast occurrence along the SE Arabian Peninsula. The remaining three zones, Peru-Chile, NW Africa, and SW Africa are between the two extremes in fog occurrence, along coast coverage and sea surface temperature. Peru-Chile is more complex than the others as the Peru upwelling and fog appears the more dominant although ship observations are sparse along Chile.

  5. Relationship between optical extinction and liquid water content in fogs

    NASA Astrophysics Data System (ADS)

    Klein, C.; Dabas, A.

    2013-11-01

    Studies carried out in the late 1970s suggest a simple linear relationship exists in practice between the optical extinction in the thermal IR and the liquid water content (LWC) in fogs. Such a relationship opens the possibility to monitor the vertical profile of the LWC in fogs with a rather simple backscatter lidar. Little is known on how the LWC varies as a function of height and during the fog life cycle, so the new measurement technique would help understand fog physics and provide valuable data for improving the quality of fog forecasts. In the present article, the validity of the linear relationship is revisited at the light of recent observations of fog droplet size distributions measured with a combination of sensors covering a large range of droplet radii. In particular, large droplets (radius above 15 μm) are detected, which was not the case in the late 1970s. The results confirm the linear relationship still holds, at least for the mostly radiative fogs observed during the campaign. The impact of the precise value of the real and imaginary parts of the refractive index on the coefficient of the linear relationship is also studied. The usual practice considers droplets are made of pure water. This assumption is probably valid for big droplets, it may be questioned for small ones since droplets are formed from condensation nuclei of highly variable chemical composition. The study suggests the relationship is mostly sensitive to the real part of the refractive index and the sensitivity grows with the size of fog droplets. However, large fog droplets are more likely to have an index close to that of water since they are mainly composed of water.

  6. Coastal Fog Sustains Summer Baseflow in Northern Californian Watershed

    NASA Astrophysics Data System (ADS)

    Chung, M.; Dufour, A.; Leonardson, R.; Thompson, S. E.; Dawson, T. E.

    2015-12-01

    The Mediterranean climate of Northern California imposes significant water stress on ecosystems and water resources during the dry summer months. During summer, frequently the only water inputs occur as occult precipitation, in the form of fog and dew. In this study, we characterized the role of coastal fog, a dominant feature of Northern Californian coastal ecosystems and a widespread phenomenon associated with deep marine upwelling in west coast, arid, and Mediterranean climates worldwide. We monitored fog occurrence and intensity, throughfall following canopy interception of fog, soil moisture, streamflow, and meteorological variables, and made visual observations of the spatial extent of fog using time-lapse imagery in Upper Pilarcitos Creek Watershed (managed by San Francisco Public Utilities Commission as part of the San Francisco area water supply). We adopted a stratified sampling design that captured the watershed's elevation gradient, forest-edge versus interior locations, and different vegetation cover. The point-scale observations of throughfall inputs and transpiration suppression, estimated from the Penman equation, were upscaled using such watershed features and the observed fog "footprint" identified from the time-lapse images. When throughfall input and fog-induced transpiration suppression were incorporated into the operational watershed model, they improved estimates of summer baseflow, which remained persistently higher than could be explained without the fog effects. Fog, although providing relatively small volumetric inputs to the water balance, appears to offer significant relief of water stress throughout the terrestrial and aquatic components of the coastal Californian ecosystem and thus should be accounted for when assessing water stress availability in dry ecosystems.

  7. Alternative Agents to Prevent Fogging in Head and Neck Endoscopy

    PubMed Central

    Piromchai, Patorn; Kasemsiri, Pornthep; Thanaviratananich, Sanguansak

    2011-01-01

    Background: The essential factor for diagnosis and treatment of diseases in head and neck endoscopy is the visibility of the image. An anti-fogging agent can reduce this problem by minimizing surface tension to prevent the condensation of water in the form of small droplets on a surface. There is no report on the use of hibiscrub® or baby shampoo to reduce fogging in the literature. The objective of this study was to compare the efficacy between commercial anti-fogging agent, hibiscrub® and baby shampoo to reduce fogging for the use in head and neck endoscopy. Methods: The study was conducted at the Department of Otorhinolaryngology, Faculty of Medicine, Khon Kaen University in August 2010. Commercial anti-fogging agent, baby shampoo and hibiscrub® were applied on rigid endoscope lens before putting them into a mist generator. The images were taken at baseline, 15 seconds, 30 seconds and 1 minute. The images’ identifiers were removed before they were sent to two evaluators. A visual analogue scale (VAS) was used to rate the image quality from 0 to 10. Results: The difference in mean VAS score between anti-fogging agent, baby shampoo and hibiscrub® versus no agent were 5.46, 4.45 and 2.1 respectively. The commercial anti-fogging agent and baby shampoo had most protective benefit and performed significantly better than no agent (P = 0.05). Conclusions: Baby shampoo is an effective agent to prevent fogging during head and neck endoscopy and compares favourably with commercial anti-fogging agent. PMID:24179399

  8. Biodegradation of fat, oil and grease (FOG) deposits under various redox conditions relevant to sewer environment.

    PubMed

    He, Xia; Zhang, Qian; Cooney, Michael J; Yan, Tao

    2015-07-01

    Fat, oil and, grease (FOG) deposits are one primary cause of sanitary sewer overflows (SSOs). While numerous studies have examined the formation of FOG deposits in sewer pipes, little is known about their biodegradation under sewer environments. In this study, FOG deposit biodegradation potential was determined by studying the biodegradation of calcium palmitate in laboratory under aerobic, nitrate-reducing, sulfate-reducing, and methanogenic conditions. Over 110 days of observation, calcium palmitate was biodegraded to CO2 under aerobic and nitrate-reducing conditions. An approximate 13 times higher CO2 production rate was observed under aerobic condition than under nitrate-reducing condition. Under sulfate-reducing condition, calcium palmitate was recalcitrant to biodegradation as evidenced by small reduction in sulfate. No evidence was found to support calcium palmitate degradation under methanogenic condition in the simulated sewer environment. Dominant microbial populations in the aerobic and nitrate-reducing microcosms were identified by Illumina seqeuncing, which may contain the capability to degrade calcium palmitate under both aerobic and nitrate-reducing conditions. Further study on these populations and their functional genes could shed more light on this microbial process and eventually help develop engineering solutions for SSOs control in the future.

  9. Dominant factors controlling concentrations of aldehydes in rain, fog, dew water, and in the gas phase

    NASA Astrophysics Data System (ADS)

    Matsumoto, Kiyoshi; Kawai, Shunji; Igawa, Manabu

    Low-molecular weight aldehyde compounds in rain, fog, dew water, and in the gas phase were measured at urban and suburban mountain sites, to characterize the chemical composition of aldehydes in liquid droplets and in the gas phase in the ambient atmosphere, and discuss the factors controlling wet removal processes of aldehydes. Higher concentrations of total aldehydes were found in dew water than in rain and fog water due to the small amount of water volume. Both formaldehyde and acetaldehyde were detected as dominant aldehydes in the gas phase. Secondary formation processes are dominant sources for both aldehydes in the suburban site, whereas primary sources are relatively important for the urban atmosphere. In rainwater, by contrast, formaldehyde was the most abundant aldehyde, followed by glyoxal. Glyoxal was detected as the most dominant aldehyde in fog and dew water. Acetaldehyde was not detected as a main component in liquid droplets in spite of its abundance in the gas phase. Water solubility of each aldehyde compound and dilution effect by water are critical factors that control the compositions and concentrations of these aldehydes in ambient liquid droplets.

  10. Environmental and Health Effects Review for Obscurant Fog Oil

    DTIC Science & Technology

    1993-09-01

    fog oil and other materials will be by specific name. 2.3.1 Physical Characteristics The physical characteristics of fog oil are listed in MIL-F-12070C...oil 17 was applied to less than 2% of the shell surface (Albers 1976; Szaro and Albers 1976), indicating the embryotoxic capacity of the lubricating...4.6.4 Djsps1 Fog oil is not listed as a hazardous waste under RCRA. 33 5. CONCLUSIONS Evaluations based on modeled estimates and scientific studies

  11. Advection, diffusion, and delivery over a network.

    PubMed

    Heaton, Luke L M; López, Eduardo; Maini, Philip K; Fricker, Mark D; Jones, Nick S

    2012-08-01

    Many biological, geophysical, and technological systems involve the transport of a resource over a network. In this paper, we present an efficient method for calculating the exact quantity of the resource in each part of an arbitrary network, where the resource is lost or delivered out of the network at a given rate, while being subject to advection and diffusion. The key conceptual step is to partition the resource into material that does or does not reach a node over a given time step. As an example application, we consider resource allocation within fungal networks, and analyze the spatial distribution of the resource that emerges as such networks grow over time. Fungal growth involves the expansion of fluid filled vessels, and such growth necessarily involves the movement of fluid. We develop a model of delivery in growing fungal networks, and find good empirical agreement between our model and experimental data gathered using radio-labeled tracers. Our results lead us to suggest that in foraging fungi, growth-induced mass flow is sufficient to account for long-distance transport, if the system is well insulated. We conclude that active transport mechanisms may only be required at the very end of the transport pathway, near the growing tips.

  12. International evolution of fat, oil and grease (FOG) waste management - A review.

    PubMed

    Wallace, Thomas; Gibbons, David; O'Dwyer, Michael; Curran, Thomas P

    2017-02-01

    In recent years, issues relating to fat, oil and grease (FOG) in sewer systems have intensified. In the media, sewer blockages caused by FOG waste deposits, commonly referred to as 'fatbergs', are becoming a reminder of the problems that FOG waste can cause when left untreated. These FOG blockages lead to sanitary sewer overflows, property flooding and contamination of water bodies with sewage. Despite these financial and environmentally detrimental effects, a homogenous FOG waste management method has not been developed internationally. However, some successful enduring FOG management programmes have been established, such as in Dublin city and in Scandinavian countries. The aim of this paper is to carry out a review on existing FOG research and management approaches. FOG management involves comprehending: (1) FOG deposition factors in the sewer, (2) FOG prevention and awareness tactics undertaken internationally and (3) potential utilisation methods for FOG waste. This review will highlight that preventing FOG from entering the sewer is the most common approach, often through simple awareness campaigns. The diverted FOG is rarely valorised to bioenergy or biomaterials, despite its potential. Thus, all facets of the FOG waste lifecycle must be identified and managed. Advancements in processes and techniques must be assessed to best determine the future evolution of FOG waste management to assist in achieving a sustainable urban environment.

  13. Meteorological Patterns and Fog Water in the Canary Islands and Morocco

    NASA Astrophysics Data System (ADS)

    Marzol, M. V.; Sanchez Megía, J. L.; Yanes, A.; Bargach, J.; Derhem, A.

    2010-07-01

    The Stratocumulus cloud formation is very common in the Canary Islands (Spain) and on the Atlantic coast of Morocco. This cloud formation behaves as if it was fog when it comes into contact with the relief and its liquid content can be captured by artificial systems. The origin of this cloud formation is connected with the Azores anti-cyclone and with the anomalous structure of the low layers of the atmosphere caused by a subsidence thermal inversion. The aim of this article is to define a pattern of the most favourable meteorological and atmospheric conditions for this cloud formation to appear. In order to do this, a database has been compiled with the information about the days on which water has been collected in Morocco since June, 2006. This was when the collaboration with the Si Hmad Derhem Foundation (Casablanca) began. As well as meteorological data and data on water quantities, weather maps, thermodynamic soundings and satellite images are also analysed. The following two sites were studied: Anaga, on the island of Tenerife, Canary Islands, 864 m a.s.l. and 4 km from the coast, and Boutmezguida, Morocco, 1,225 m a.s.l. and 30 km from the coast. The research was conducted in three stages. The first stage consisted of looking for the most appropriate sites to obtain the greatest efficiency in fog water collection; the Standard Fog Collector (SFC, Schemenauer and Cereceda, 1994) was used for this purpose. The second stage consisted of studying the most favourable meteorological conditions for water collection where the Quarter Fog Collector (QFC, Marzol, 2002) connected to an automatic weather station providing information on temperature, humidity, precipitation, wind speed and direction and the amount of water collected on the netting every ten minutes was used to do this. The aim of the third stage, which was by nature an applied stage, was to construct large-sized fog collectors (Large Fog Collector, LFC) so that the water collected could be put to

  14. GOES-derived fog and low cloud indices for coastal north and central California ecological analyses

    USGS Publications Warehouse

    Torregrosa, Alicia; Cindy Combs,; Peters, Jeff

    2015-01-01

    Fog and low cloud cover (FLCC) changes the water, energy, and nutrient flux of coastal ecosystems. Easy-to-use FLCC data are needed to quantify the impacts of FLC on ecosystem dynamics during hot, dry Mediterranean climate summers. FLCC indices were generated from 26,000 hourly night and day FLCC maps derived from Geostationary Environmental Operational Satellite (GOES) data for June, July, August, and September, 1999- 2009 for coastal California, latitude 34.50°N, south of Monterey Bay, to latitude 41.95°N, north of Crescent City. Monthly FLCC average hours per day (h/d) range from < 2 to 18. Average FLCC over the ocean increases from north (9 h/d) to south (14 h/d) whereas FLCC over land is reversed. Over land, FLCC is highest where land juts into the prevailing NW winds and is lowest in the lee of major capes. FLCC advects furthest inland through low-lying NW ocean-facing valleys. At night hours of FLCC is higher more frequently on land than over the ocean. Interannual FLCC coefficient of variation shows long term geographic stability strongly associated with landform position. Contours delineating homogeneous zones of FLCC, derived from average decadal h/d FLCC, provide data to refine the commonly used term ‘fog belt.’ FLCC indices are available for download from the California Landscape Conservation Cooperative Climate Commons website. FLCC indices can be used to improve analyses of biogeographic and bioclimatic species distribution models, meteorological mechanisms driving FLCC patterns, ecohydrological investigations of evapotranspiration, solar energy feasibility studies, agricultural irrigation demand and viticultural ripening models.

  15. Charged particle concepts for fog dispersion

    NASA Technical Reports Server (NTRS)

    Frost, W.; Collins, F. G.; Koepf, D.

    1981-01-01

    Charged particle techniques hold promise for dispersing warm fog in the terminal area of commercial airports. This report focuses on features of the charged particle technique which require further study. The basic physical principles of the technique and the major verification experiments carried out in the past are described. The fundamentals of the nozzle operation are given. The nozzle characteristics and the theory of particle charging in the nozzle are discussed, including information from extensive literature on electrostatic precipitation relative to environmental pollution control and a description of some preliminary reported analyses on the jet characteristics and interaction with neighboring jets. The equation governing the transfer of water substances and of electrical charge is given together with a brief description of several semi-empirical, mathematical expressions necessary for the governing equations. The necessary ingredients of a field experiment to verify the system once a prototype is built are described.

  16. Modeling the advection of discontinuous quantities in Geophysical flows using Particle Level Sets

    NASA Astrophysics Data System (ADS)

    Aleksandrov, V.; Samuel, H.; Evonuk, M.

    2010-12-01

    Advection is one of the major processes that commonly acts on various scales in nature (core formation, mantle convective stirring, multi-phase flows in magma chambers, salt diapirism ...). While this process can be modeled numerically by solving conservation equations, various geodynamic scenarios involve advection of quantities with sharp discontinuities. Unfortunately, in these cases modeling numerically pure advection becomes very challenging, in particular because sharp discontinuities lead to numerical instabilities, which prevent the local use of high order numerical schemes. Several approaches have been used in computational geodynamics in order to overcome this difficulty, with variable amounts of success. Despite the use of correcting filters or non-oscillatory, shock-preserving schemes, Eulerian (fixed grid) techniques generally suffer from artificial numerical diffusion. Lagrangian approaches (dynamic grids or particles) tend to be more popular in computational geodynamics because they are not prone to excessive numerical diffusion. However, these approaches are generally computationally expensive, especially in 3D, and can suffer from spurious statistical noise. As an alternative to these aforementioned approaches, we have applied a relatively recent Particle Level set method [Enright et al., 2002] for modeling advection of quantities with the presence of sharp discontinuities. We have tested this improved method, which combines the best of Eulerian and Lagrangian approaches, against well known benchmarks and classical Geodynamic flows. In each case the Particle Level Set method accuracy equals or is better than other Eulerian and Lagrangian methods, and leads to significantly smaller computational cost, in particular in three-dimensional flows, where the reduction of computational time for modeling advection processes is most needed.

  17. Fast and accurate advection of sharp discontinuities in Geophysical flows using hybrid implicit surfaces

    NASA Astrophysics Data System (ADS)

    Samuel, Henri

    2010-05-01

    Advection is one of the major processes that commonly acts on various scales in nature (core formation, mantle convective stirring, multi-phase flows in magma chambers, salt diapirism ...). While this process can be modeled numerically by solving conservation equations, various geodynamic scenarios involve advection of quantities with sharp discontinuities. Unfortunately, in these cases modeling numerically pure advection becomes very challenging, in particular because sharp discontinuities lead to numerical instabilities, which prevent the local use of high order numerical schemes. Several approaches have been used in computational geodynamics in order to overcome this difficulty, with variable amounts of success. Despite the use of correcting filters or non-oscillatory, shock-preserving schemes, Eulerian (fixed grid) techniques generally suffer from artificial numerical diffusion. Lagrangian approaches (dynamic grids or particles) tend to be more popular in computational geodynamics because they are not prone to excessive numerical diffusion. However, these approaches are generally computationally expensive, especially in 3D, and can suffer from spurious statistical noise. As an alternative to these aforementioned approaches, I have applied a relatively recent Particle Level set method [Enright et al., 2002] for modeling advection of quantities with the presence of sharp discontinuities. I have adapted this improved method, which combines the best of Eulerian and Lagrangian approaches, and I have tested it against well known benchmarks and classical Geodynamic flows. In each case the Particle Level Set method accuracy equals or is better than other Eulerian and Lagrangian methods, and leads to significantly smaller computational cost, in particular in three-dimensional flows, where the reduction of computational time for modeling advection processes is most needed.

  18. 2. Oil house, fog signal house and light tower, view ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. Oil house, fog signal house and light tower, view southwest, east and north sides - Great Duck Island Light Station, At southern tip of Great Duck Island southeast of Bass Harbor & northeast of Frenchboro, Frenchboro, Hancock County, ME

  19. 3. Light tower and fog signal house, view northeast, west ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. Light tower and fog signal house, view northeast, west and south sides - Great Duck Island Light Station, At southern tip of Great Duck Island southeast of Bass Harbor & northeast of Frenchboro, Frenchboro, Hancock County, ME

  20. 11. Fog signal tower, view southeast, northwest and southwest sides ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. Fog signal tower, view southeast, northwest and southwest sides - Kennebec River Light Station, South side of Doubling Point Road, off State Highway 127, 1.8 miles south of U.S. Route 1, Arrowsic, Sagadahoc County, ME

  1. 28. Photograph of interior view of fog horn signal building ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    28. Photograph of interior view of fog horn signal building with two lighthouse keepers by steam engine wheel, ca. 1920. - Block Island Southeast Light, Spring Street & Mohegan Trail at Mohegan Bluffs, New Shoreham, Washington County, RI

  2. 11. Fog signal house, view northnorthwest, east and south sides ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. Fog signal house, view north-northwest, east and south sides - Cape Elizabeth Light Station, Near Two Lights State Park at end of Two Lights Road, off State Highway 77, Cape Elizabeth, Cumberland County, ME

  3. Investigation of Sea Surface Temperature and local topography effects on coastal fog: Case study of 21-22 January 2008 event on the west coast of Morocco

    NASA Astrophysics Data System (ADS)

    Bari, Driss; Bergot, Thierry; El Khlifi, Mohamed

    2014-05-01

    The life cycle of fog over coastal regions is very sensitive to the heterogeneity of the landform and to the vicinity to the Ocean. Thus, the influence of the sea surface temperature (SST) and local topography on the evolution of a coastal fog is assessed in this study by performing sensitivity experiments. To achieve this, the numerical simulations are performed with the three-dimensional research model Meso-NH. This fog event occurred at the Grand Casablanca region, in the northwest coast of Morocco, during the night of 21-22 January 2008 and last more than 12 hours. It was analyzed using standard meteorological observations from the two synoptic stations of the region, the observed radio-sounding at the coastal station, the MSG satellite imagery and the ECMWF ERA-Interim reanalysis. The numerical simulation reproduced well the main features of this fog event since its formation to its dissipation. The numerical results demonstrated that this fog event was of a radiation type over land, due to the nocturnal radiative cooling and the turbulence. And one hour later near the coast, the fog was resulting from base lowering of Stratus low cloud, due to the cloud top cooling and the vertical turbulent mixing. The sensitivity experiments to SST demonstrate that varying SST in space and time affects the spatial distribution of the fog layer over an area of about 20km around the coast. Besides, the SST governs the thermodynamic fluxes at the air-sea interface, and then affects the life cycle of this fog event, in particular in the mature and dissipation phases. On the other hand, the sensitivity experiments to local coastal topography demonstrated its impact on the speed and direction of wind in the boundary layer during the different phases of the life cycle of this fog event. Then, it was found that the heterogeneities of terrain over the coastal regions affect the horizontal extension of this fog event during the mature phase and its evolution during the dissipation

  4. Urbanization Effects on Fog in China: Field Research and Modeling

    NASA Astrophysics Data System (ADS)

    Li, Zi-hua; Yang, Jun; Shi, Chun-e.; Pu, Mei-juan

    2012-05-01

    Since the policy of "Reform and Open to the Outside World" was implemented from 1978, urbanization has been rapid in China, leading to the expansion of urban areas and population synchronous with swift advances in economy. With urban development underway, the urban heat island (UHI) and air pollution are being enhanced, together with vegetation coverage and relative humidity on the decrease. These changes lead to: (1) decline of annual fog days in cities (e.g. In Chongqing, so-called city of fog in China, the annual fog days have reduced from 100-145 in the 1950s to about 20-30 in the 2000s); (2) decrease in fog water content (FWC) and fog droplet size, but increase in fog droplets number concentration [e.g. Jinghong, a city in Yunnan province, the average FWC (the droplet diameter) during an extremely dense fog episode with drizzle was 0.74 g/m3 (28.6 μm) during the 1968/69 winter and 0.08 g/m3 (6.8 μm) in another extremely dense fog episode during the 1986/87 winter, correspondingly, the fog droplets number density had increased from 34.9 to 153 cm-3]; (3) decrease in fog water deposition (FWD) (e.g. the annual mean FWD measured in Jinghong had dropped from 17.3 mm in the 1950s to 4.4 mm in the 1970s and less than 1 mm in the 1980s, and no measurable FWD now.); (4) decrease in visibility in large cities (e.g. in Chongqing, the annual average visibility had decreased from 8.2-11.8 km in the 1960s to 4.9-6.5 km in the 1980s, and around 5 km in recent years); and (5) increase in the ion concentrations and acidity in fog water in urban areas [e.g. the average total ion concentration (TIC) in the center of Chongqing was 5.5 × 104 μmol/L, with mean pH value of 4.0, while the corresponding values are 9.7 × 103 μmol/L and over 5.5 in its rural area]. These changes endanger all kinds of transportation and human health. This paper summarized the authors' related studies, including observations and numerical simulations to confirm the above conclusions.

  5. Measurements of fog composition at a rural site

    NASA Astrophysics Data System (ADS)

    Straub, Derek J.; Hutchings, James W.; Herckes, Pierre

    2012-02-01

    Studies that focus on fog chemistry in the United States have been limited to relatively few locations. Apart from measurements along the East and West coasts and extensive analysis of radiation fog in the Central Valley of California, fog composition has been characterized in only a handful of other locations. To complement and expand the existing fog chemistry data that are currently available, a new field campaign was established at a rural location in Central Pennsylvania to produce a unique, long term record of fog composition. From 2007 to 2010, 41 fog events were sampled with an automated Caltech Heated Rod Cloudwater Collector (CHRCC). The collected samples were analyzed primarily for pH and major inorganic ions. Dissolved organic carbon (DOC) and trace metals were analyzed in selected samples and N-nitrosodimethylamine (NDMA) was quantified in two samples. Sample composition varied widely during the study period. Sulfate concentrations ranged from 15 to 955 (median = 123) μN and pH varied between 3.08 and 7.41 (median = 5.77). In terms of volume weighted averages, ammonium was the most abundant ionic species followed by sulfate, calcium, and nitrate. For the subset of samples in which DOC was analyzed, concentrations ranged from 2.2 to 22.6 mgC l -1. Comparisons with regional precipitation chemistry measurements reveal the influence of local agricultural and soil sources on fog composition. The sum of sulfate, nitrate, and ammonium measured in the present study is considerably lower than the majority of radiation, precipitation, and coastal fogs collected in the United States although the ammonium/(nitrate + sulfate) ratio is similar to those found in the Central Valley of California.

  6. Vertical profile of fog microphysics : a case study

    NASA Astrophysics Data System (ADS)

    Burnet, Frédéric; Brilouet, Pierre-Etienne; Mazoyer, Marie; Bourrianne, Thierry; Etcheberry, Jean-Michel; Gaillard, Brigitte; Legain, Dominique; Tzanos, Diane; Barrié, Joel; Barrau, Sébastien; Defoy, Stephan

    2016-04-01

    The occurrence and development of fogs result from the non-linear interaction of competing radiative, thermodynamic, microphysical and dynamical processes and the forecasting of their life cycle still remains a challenging issue. Several field campaigns have been carried out at the SIRTA observatory in the Paris suburb area (France). These experiments have shown that fog events exhibit large differences of the microphysical properties and various evolutions during their life cycle. To better understand relationships between the different processes and to validate numerical simulations it is necessary however to document the vertical profile of the fog microphysics. A CDP (Cloud Droplet Spectrometer) from DMT (Droplet Measurement Technology, Boulder, CO) has been modified to allow measurements of the droplet size distribution in fog layers with a tethered balloon. This instrumental set-up has been used during a field campaign during the winter 2013-214 in the Landes area in the South West of France. To validate the vertical profiles provided by the modified CDP, a mast was equipped with microphysical instruments at 2 altitude levels with an another CDP at 24 m and a Fog Monitor FM100 at 42 m. The instrumental set-up deployed during this campaign is presented. Data collected during a fog event that occurred during the night of 5-6 March 2014 are analysed. We show that microphysical properties such as droplet number concentration, LWC and mean droplet size, exhibit different time evolution during the fog life cycle depending on the altitude level. Droplet size distribution measurements are also investigated. They reveal sharp variations along the vertical close to the top of the fog layer. In addition it is shown that the shape of the size distributions at the top follows a time evolution typical of a quasi-adiabatic droplet growth.

  7. Relationship between optical extinction and liquid water content in fogs

    NASA Astrophysics Data System (ADS)

    Klein, C.; Dabas, A.

    2014-05-01

    Studies carried out in the late 1970s suggest that a simple linear relationship exists in practice between the optical extinction in the thermal IR and the liquid water content (LWC) in fogs. Such a relationship opens the possibility to monitor the vertical profile of the LWC in fogs with a rather simple backscatter lidar. Little is known on how the LWC varies as a function of height and during the fog life cycle, so the new measurement technique would help understand fog physics and provide valuable data for improving the quality of fog forecasts. In this paper, the validity of the linear relationship is revisited in the light of recent observations of fog droplet size distributions measured with a combination of sensors covering a large range of droplet radii. In particular, large droplets (radius above 15 μm) are now detected, which was not the case in the late 1970s. The results confirm that the linear relationship still holds, at least for the mostly radiative fogs observed during the campaign. The impact of the precise value of the real and imaginary parts of the refractive index on the coefficient of the linear relationship is also studied. The usual practice considers that droplets are made of pure water. This assumption is probably valid for big drops, but it may be questioned for small ones since droplets are formed from condensation nuclei of highly variable chemical composition. The study suggests that the precise nature of condensation nuclei will primarily affect rather light fogs with small droplets and light liquid water contents.

  8. Designing for chaos: applications of chaotic advection at the microscale.

    PubMed

    Stremler, Mark A; Haselton, F R; Aref, Hassan

    2004-05-15

    Chaotic advection can play an important role in efficient microfluidic mixers. We discuss a design paradigm that exploits chaotic advection and illustrate by two recent examples, namely enhancing gene expression profiling and constructing an in-line microfluidic mixing channel, how application of this paradigm has led to successful micromixers. We suggest that 'designing for chaos', that is, basing practical mixer design on chaotic advection analysis, is a promising approach to adopt in this developing field which otherwise has little to guide it and is constrained by issues of scale and manufacturability.

  9. Problems, control, and treatment of fat, oil, and grease (FOG): a review.

    PubMed

    Husain, Iman A F; Alkhatib, Ma'an Fahmi; Jammi, Mohamed Saedi; Mirghani, Mohamed E S; Bin Zainudin, Zaki; Hoda, Asif

    2014-01-01

    Presence of fat, oil, and grease (FOG) in wastewater is an ever-growing concern to municipalities and solid-waste facility operators. FOG enters the sewer system from restaurants, residences, and industrial food facilities. Its release into the sewer system results in a continuous build-up that causes eventual blockage of sewer pipes. Several researchers have investigated FOG deposition based on the local conditions of sewers and lifestyle. This paper attempts to review the physical and chemical characteristics of FOG, sources of FOG, and potential chemical and biological reactions of FOG. The effect of the aforementioned factors on the FOG-deposition mechanism is also discussed. Moreover, insight into the current control and treatment methods and potential reuse of FOG is highlighted. It is expected that this review would provide scientists and the concerned authorities a holistic view of the recent researches on FOG control, treatment, and reuse.

  10. A Comparison of the Efficiency Between Fog Collecting Meshes

    NASA Astrophysics Data System (ADS)

    Eljenholm, C. M.; Coffey, E. M.; Fernandez, D.; Hernandez, C.; Mairs, A. A.

    2014-12-01

    Precipitation is the most recognized source of water; however, significant amounts of water reside in the air in the form of fog. Standard fog collectors designed by Schemenauer (Schemenauer and Cereceda, 1993) utilize a 1.00 square meter of a specific polypropylene fabric called Coresa with a 35% Raschel shade coefficient to capture and coalesce tiny fog droplets into larger drops that fall into a trough and are measured by a tipping bucket rain gauge. In this study, we compare three different types of mesh; the Chilean Coresa mesh mentioned above, a German mesh called FogHa-Tin, and an optimized mesh designed at the Massachusetts Institute of Technology, a POSS-PEMA dipped metallic mesh (Park et al, 2013). These meshes vary greatly in composition, as well as price. In order to determine which mesh is most optimal for fog collection in a variety of meteorological conditions, standard collectors of each type described above with a mesh area of 1.00 square meter have been placed at five locations around central California with accompanying meteorological instrumentation. This project will report on the effectiveness of each of these passive fog collectors in conjunction with accompanying meteorological data.

  11. Mathematical modeling of acid deposition due to radiation fog

    SciTech Connect

    Pandis, S.N.; Seinfeld, J.H. )

    1989-09-20

    A Lagrangian model has been developed to study acidic deposition due to radiation fog. The model couples submodels describing the development and dissipation of radiation fog, the gas-phase chemistry and transfer, and the aqueous-phase chemistry. The model is applied to a radiation fog episode in Bakersfield in the San Joaquin Valley of California over the period January 4--5 1985. Model predictions for temperature profile, fog development, liquid water content, gas-phase concentrations of SO{sub 2}, HNO{sub 3}, and NH{sub 3}, {ital p}H, aqueous-phase concentrations of OS{sup 2{minus}}{sub 4}, NH{sup +}{sub 4}, and NO{sup {minus}}{sub 3}, and finally deposition rates of the above ions are compared with the observed values. The deposition rates of the major ions are predicted to increase significantly during the fog episode, the most notable being the increase of sulfate deposition. Pathways for sulfate production that are of secondary importance in a cloud environment may become signficant in a fog. Expressing the mean droplet settling velocity as a function of liquid water content is found to be quite influential in the model's predictions. {copyright} American Geophysical Union 1989

  12. Retrieval of Fog Microphysical Parameters from NOAA AVHRR Data

    NASA Astrophysics Data System (ADS)

    Xu, Ling

    1995-01-01

    Identifying the droplet size distribution, frequency and location of land-based fog is valuable for climate studies, because of the effects on agricultural productivity projections, highway traffic safety, and urban pollution monitoring. It's especially important to the Central Valley of California, which frequently suffers lingering, heavy fog. Land-based fog plays an important role in surface radiation budgets, by blocking daytime solar heating and nocturnal long wave cooling. The droplet size distribution determines the optical depth and radiative attenuation of fog. An operational retrieval method for obtaining droplet size and optical depth has been developed for land -based fog from the multichannel NOAA (National Oceanic and Atmospheric Administration) AVHRR (Advanced Very High Resolution Radiometer) digital image data. The visible and near infrared images provide the reflectances of both channels, which vary with droplet microphysical characteristics. The reflectances are interpolated to radiative cloud modeling results. A new field method has been used for obtaining the measurements of land-based fog microphysical and thermodynamic parameters. A tethered balloon carries a meteorological package and a cloud droplet imaging system which transfer the images to a recording system on the ground. The results from the satellite imagery at Esparto (ESP), California are well matched with field sampling results at the same location.

  13. Microphysics and energy and water fluxes of various fog types at SIRTA, France

    NASA Astrophysics Data System (ADS)

    Degefie, D. T.; El-Madany, T.-S.; Hejkal, J.; Held, M.; Dupont, J.-C.; Haeffelin, M.; Klemm, O.

    2015-01-01

    During the PARISFOG campaign in winter 2012/2013, microphysical properties and turbulent fluxes of fog droplets (liquid water), water vapor, and energy were characterized and quantified during fog events of various types that occurred at the SIRTA (Site Instrumental de Recherche par Télédétection Atmosphérique) atmospheric observatory outside Paris. The eddy covariance technique was applied, employing a fast (10 Hz) fog droplet spectrometer, a three-dimensional ultrasonic anemometer, and a fast response gas analyzer, which were operated at an altitude of 2.5 m above ground. A visibility meter was used to detect the occurrence and density of fog. A total of twenty-one fog events were measured during the field campaign. After applying quality criteria, six events remained. For this study, two fog events out of the six, representing a radiation fog and stratus lowering fog, respectively, are analyzed in detail. The two fog events exhibited very distinct patterns in terms of fog droplet size distribution, fog number concentration, and liquid water content. The evolution of these microphysical properties is elucidated through combined analysis of the turbulent fluxes of fog droplets (liquid water), water vapor and energy as well as reasoning of microphysical processes like, condensation, collision-coalescence, and droplet evaporation. Downward droplet number fluxes and liquid water fluxes were mostly observed in stratus lowering fog, however, upward fluxes were also observed in response to downward water vapor fluxes. In radiation fog, both upward and downward droplet number fluxes and liquid water fluxes were observed depending on the position at which the microphysical process was observed with respect to the measurement height. Bi-directional fog droplet fluxes with different flux directions of smaller and larger droplets were observed. In both fog events, the downward water vapor fluxes were the major cause for (I) the broadening of the fog droplet size

  14. Flutter signal extracting technique based on FOG and self-adaptive sparse representation algorithm

    NASA Astrophysics Data System (ADS)

    Lei, Jian; Meng, Xiangtao; Xiang, Zheng

    2016-10-01

    Due to various moving parts inside, when a spacecraft runs in orbits, its structure could get a minor angular vibration, which results in vague image formation of space camera. Thus, image compensation technique is required to eliminate or alleviate the effect of movement on image formation and it is necessary to realize precise measuring of flutter angle. Due to the advantages such as high sensitivity, broad bandwidth, simple structure and no inner mechanical moving parts, FOG (fiber optical gyro) is adopted in this study to measure minor angular vibration. Then, movement leading to image degeneration is achieved by calculation. The idea of the movement information extracting algorithm based on self-adaptive sparse representation is to use arctangent function approximating L0 norm to construct unconstrained noisy-signal-aimed sparse reconstruction model and then solve the model by a method based on steepest descent algorithm and BFGS algorithm to estimate sparse signal. Then taking the advantage of the principle of random noises not able to be represented by linear combination of elements, useful signal and random noised are separated effectively. Because the main interference of minor angular vibration to image formation of space camera is random noises, sparse representation algorithm could extract useful information to a large extent and acts as a fitting pre-process method of image restoration. The self-adaptive sparse representation algorithm presented in this paper is used to process the measured minor-angle-vibration signal of FOG used by some certain spacecraft. By component analysis of the processing results, we can find out that the algorithm could extract micro angular vibration signal of FOG precisely and effectively, and can achieve the precision degree of 0.1".

  15. Fogs and Clouds are a Potential Indicator of a Local Water Source in Valles Marineris

    NASA Astrophysics Data System (ADS)

    Leung, Cecilia W. S.; Rafkin, Scot C. R.; Stillman, David E.; McEwen, Alfred S.

    2016-04-01

    Recurring slope lineae (RSL) are narrow, low-albedo seasonal flow features on present-day Mars that extend incrementally down warm, steep slopes, fade when inactive, and reappear annually over multiple Mars years [1,2]. Hypothesis for the sources of volatile by which RSL are recharged include seeping water, melting shallow ice, aquifers, and vapor from the atmosphere [1-5]. About 50% of the 250+ candidate and confirmed RSL sites appear in and around Valles Marineris [3], and coincide with regions where putative morning water ice fogs may appear as imaged by the High Resolution Stereo Camera on Mars Express [6]. The presence of fog may provide clues to the water cycle within the canyon, and could elucidate the processes related to the evolution of RSL. Using a regional atmospheric model, we investigate the atmospheric dynamics in and around Valles Marineris. Our simulation results show a curious temperature structure, where the inside of the canyon appears warmer relative to the plateaus immediately outside at all times of day. Formation of fogs requires the atmosphere to be saturated. This can happen with the appropriate combination of cooling or addition of water vapor. The modeled temperature structure suggests that if water is well mixed and fog is present within the warmer canyon bottom, fog should be present on the cooler surrounding plateaus as well. This is generally not the case. Therefore, the only way to produce fog inside the canyon is to have a local water source. RSL may contribute to this atmospheric water through evaporation, or RSL may simply be a surface marker of a larger near-surface reservoir of water that can act as a source. From the modeled temperatures, we calculated the corresponding saturation vapor pressures and saturation mixing ratios to determine the amount of water vapor in the air at saturation. The observed Martian atmospheric column abundance is ~10 precipitable microns on average [7] and presents a major challenge for an

  16. Anomalous scaling of a scalar field advected by turbulence

    SciTech Connect

    Kraichnan, R.H.

    1995-12-31

    Recent work leading to deduction of anomalous scaling exponents for the inertial range of an advected passive field from the equations of motion is reviewed. Implications for other turbulence problems are discussed.

  17. Overcoming diffusion-limited processes using enhanced advective fields

    SciTech Connect

    Rasmussen, T.C.

    1995-12-31

    Many subsurface cleanup activities focus on the remediation of organic contaminants using induced advective fields. Subsurface heterogeneities cause most advective transport to occur in more permeable zones, with transport from the lower permeability units being limited by diffusion to the higher permeable units. While diffusion rates can be enhanced using thermal sources, many of the treatment strategies, including pump and treat, vapor extraction and bioremediation, are limited by mass exchange rates between the higher and lower permeability sand and clay mixtures. Instead of relying on the enhancement of diffusion rates, it is proposed that remediation strategies should focus on the enhancement of induced advective transport rates through the lower permeability units. Injection-extraction strategies using crosshole and huff-and-puff methods are presented for maximizing advective transport through lower permeability units. Optimization of the design can incorporate diffusion-enhancement technologies, bionourishment, capillary confinement in the unsaturated zone, and DNAPL slurping.

  18. The effect of advection on the nutrient reservoir in the North Atlantic subtropical gyre.

    PubMed

    Palter, Jaime B; Lozier, M Susan; Barber, Richard T

    2005-09-29

    Though critically important in sustaining the ocean's biological pump, the cycling of nutrients in the subtropical gyres is poorly understood. The supply of nutrients to the sunlit surface layer of the ocean has traditionally been attributed solely to vertical processes. However, horizontal advection may also be important in establishing the availability of nutrients. Here we show that the production and advection of North Atlantic Subtropical Mode Water introduces spatial and temporal variability in the subsurface nutrient reservoir beneath the North Atlantic subtropical gyre. As the mode water is formed, its nutrients are depleted by biological utilization. When the depleted water mass is exported to the gyre, it injects a wedge of low-nutrient water into the upper layers of the ocean. Contrary to intuition, cold winters that promote deep convective mixing and vigorous mode water formation may diminish downstream primary productivity by altering the subsurface delivery of nutrients.

  19. Constraints upon water advection in sediments of the Mariana Trough

    SciTech Connect

    Abbott, D.H.; Menke, W.; Morin, R.

    1983-02-10

    Thermal gradient measurements, consolidation tests, and pore water compositions from the Mariana Trough imply that water is moving through the sediments in areas with less than about 100 m of sediment cover. The maximum advection rates implied by the thermal measurements and consolidation tests may be as high as 10/sup -5/ cm s/sup -1/ but are most commonly in the range of 1 to 5 x 10/sup -6/ cm s/sup -1/. Theoretical calculations of the effect of the highest advection rates upon carbonate dissolution indicate that dissolution may be impeded or enhanced (depending upon the direction of flow) by a factor of 2 to 5 times the rate for diffusion alone. The average percentage of carbonate is consistently higher in two cores from the area with no advection or upward advection than the average percentage of carbonate in three cores from the area with downward advection. This increase in average amount of carbonate in cores with upward moving water or no movement cannot be attributed solely to differences in water depth or in amount of terrigenous dilution. If the sediment column acts as a passive boundary layer, then the water velocities necessary to affect chemical gradients of silica are in the range 10/sup -9/ to 10/sup -10/ cm s/sup -1/. However, if dissolution of silica occurs within the sediment column, then the advection velocities needed to affect chemical gradients are at least 3 x 10/sup -8/ cm s/sup -1/ and may be as high as 3 x 10/sup -6/ cm s/sup -1/. This order of magnitude increase in advection velocities when chemical reactions occur within the sediments is probably applicable to other cations in addition to silica. If so, then the advection velocities needed to affect heat flow (>10/sup -8/ cm s/sup -1/) and pore water chemical gradients are much nearer in magnitude than previously assumed.

  20. Advection around ventilated U-shaped burrows: A model study

    NASA Astrophysics Data System (ADS)

    Brand, Andreas; Lewandowski, JöRg; Hamann, Enrico; Nützmann, Gunnar

    2013-05-01

    Advective transport in the porous matrix of sediments surrounding burrows formed by fauna such as Chironomus plumosus has been generally neglected. A positron emission tomography study recently revealed that the pumping activity of the midge larvae can indeed induce fluid flow in the sediment. We present a numerical model study which explores the conditions at which advective transport in the sediment becomes relevant. A 0.15 m deep U-shaped burrow with a diameter of 0.002 m within the sediment was represented in a 3-D domain. Fluid flow in the burrow was calculated using the Navier-Stokes equation for incompressible laminar flow in the burrow, and flow in the sediment was described by Darcy's law. Nonreactive and reactive transport scenarios were simulated considering diffusion and advection. The pumping activity of the model larva results in considerable advective flow in the sediment at reasonable high permeabilities with flow velocities of up to 7.0 × 10-6 m s-1 close to the larva for a permeability of 3 × 10-12 m2. At permeabilities below 7 × 10-13 m2 advection is negligible compared to diffusion. Reactive transport simulations using first-order kinetics for oxygen revealed that advective flux into the sediment downstream of the pumping larva enhances sedimentary uptake, while the advective flux into the burrow upstream of the larvae inhibits diffusive sedimentary uptake. Despite the fact that both effects cancel each other with respect to total solute uptake, the advection-induced asymmetry in concentration distribution can lead to a heterogeneous solute and redox distribution in the sediment relevant to complex reaction networks.

  1. An Evaluation of Marine Fog Forecast Concepts and a Preliminary Design for a Marine Obscuration Forecast System.

    DTIC Science & Technology

    1983-06-01

    SNU 4n.aa 0.4 U - 4414 00 4414 410 1 *0 = .~ ~ 0 t 0 c~a- Cr, 0. _o 0 a.4 3-. a 20 M U- 0 m - c~4 0 ’a41 -A 0 - a0- -w >, I.> C. ad -I~u1 44- -1 01a a...tY A capping urine inversion has been demonstrated as being a necessary condition for the formation of marine fog along the California coast. A

  2. Glaucoma and Driving Risk under Simulated Fog Conditions

    PubMed Central

    Diniz-Filho, Alberto; Boer, Erwin R.; Elhosseiny, Ahmed; Wu, Zhichao; Nakanishi, Masaki; Medeiros, Felipe A.

    2016-01-01

    Purpose We evaluate driving risk under simulated fog conditions in glaucoma and healthy subjects. Methods This cross-sectional study included 41 glaucoma patients and 25 age-matched healthy subjects who underwent driving simulation. Tests consisted of curve negotiation without and with fog preview at 30 m of distance and two controlled speeds (slow and fast). Inverse time-to-line crossing (invTLC) was used as metric to quantify risk; higher invTLC values indicating higher risk, as less time is available to avoid drifting out of the road. Piecewise regression models were used to investigate the relationship between differences in invTLC in fog and nonfog conditions and visual field loss. Results Glaucoma patients had greater increase in driving risk under fog compared to controls, as indicated by invTLC differences (0.490 ± 0.578 s−1 and 0.208 ± 0.106 s−1, respectively; P = 0.002). Mean deviation (MD) of the better eye was significantly associated with driving risk under fog, with a breakpoint of −9 dB identified by piecewise regression. For values below the breakpoint, each 1 dB lower MD of better eye was associated with 0.117 s−1 higher invTLC under fast speed (adjusted R2 = 57.9%; P < 0.001). Conclusions Glaucoma patients have a steeper increase in driving risk under fog conditions when compared to healthy subjects, especially when the severity of visual field damage falls below −9 dB of MD in the better eye. Translational Relevance By investigating the relationship between driving risk and disease severity breakpoint, this study may provide guidance to clinicians in recognizing glaucoma patients who may be unfit to drive in complex situations such as fog. PMID:27980878

  3. Ocular Findings in Volcanic Fog Induced Conjunctivitis

    PubMed Central

    Lagunzad, John Kenneth D

    2011-01-01

    Objective To describe the ocular signs and symptoms of patients complaining of eye irritation due to volcanic fog (vog). Methods The study utilized a non-comparative, retrospective chart review of 30 patients who had a chief complaint of eye irritation, which the subjects attributed to vog. Ocular signs and symptoms are described and related to the ambient concentration of sulfur dioxide (SO2), particulate matter sized 2.5 microns (PM2.5), and vog visibility in O‘ahu during the period of the study. Results Ocular signs noted were conjunctival injection (100%), clear mucous discharge (100%), papillary reaction (100%), punctal edema (80%), eyelid swelling (73.3%) and chemosis (63.3%). Ocular symptoms were itchiness (100%), foreign body sensation (100%), tearing (96.6%) and burning sensation (90%). All patients had concurrent respiratory symptoms. During the period of study, the highest 24-hour average concentration of particulate matter sized 2.5 microns (PM2.5) was 49.04 µg/m3 and vog was visually present. Conclusions Patients complaining of eye irritation due to vog have observable ocular signs and symptoms. PMID:22187513

  4. Coastal fog prediction with a coupled model (1D+3D) system using the data from a 300 m met tower as input

    NASA Astrophysics Data System (ADS)

    Kim, W.; Yum, S. S.

    2015-12-01

    Visibility degradation due to fog can be very hazardous both to ground transportation and aviation traffic. However, prediction of fog using numerical models is difficult because fog formation is usually determined by local meteorological conditions that are hard to be measured and modeled with sufficient resolution. For this reason, there have been several attempts to build a coupled system of a fine resolution 1D model and a 3D mesoscale model with a usual grid resolution. In this study we uses the coupled system of the 1D PAFOG model and the 3D WRF model to simulate fogs formed at a southern coastal region of Korea, where the National Center for Intensive Observation of Severe Weather (NCIO) is located. Unique to NCIO is that it has a 300 m meteorological tower on which some basic meteorological variables (temperature, dew point temperature and winds) are measured at eleven different altitudes. In addition comprehensive cloud physics measurements are made with various remote sensing instruments such as cloud radar, wind profiler, microwave radiometer, micro rain radar. Several fog cases are identified during 2015 and will be simulated by the coupled system. The comprehensive set of measurement data from NCIO will be utilized as input to the model system and for evaluating the results. Particularly the data for initial and boundary conditions, which are tightly connected to the coupled model predictability, are extracted from the tower measurement. Furthermore, various sensitivity experiments will be done to enhance our understanding of the coastal fog formation mechanism. Detailed results will be discussed at the conference.

  5. The influences of macro- and microphysical characteristics of sea-fog on fog-water chemical composition

    NASA Astrophysics Data System (ADS)

    Yue, Yanyu; Niu, Shengjie; Zhao, Lijuan; Zhang, Yu; Xu, Feng

    2014-05-01

    During a sea-fog field observation campaign on Donghai Island in the spring of 2011, fog-water, visibility, meteorological elements, and fog droplet spectra were measured. The main cations and anions in 191 fog-water samples were Na+, NH{4/+}, H+, NO{3/-}, Cl- and SO{4/2-}, and the average concentrations of cations and anions were 2630 and 2970 μeq L-1, respectively. The concentrations of Na+ and Cl- originated from the ocean were high. The enhancement of anthropogenic pollution might have contributed to the high concentration of NH{4/+}, H+, and NO{3/-}. The average values of pH and electrical conductivity (EC) were 3.34 and 505 μS cm-1, respectively, with a negative correlation between them. Cold fronts associated with cyclonic circulations promoted the decline of ion loadings. Air masses from coastal areas had the highest ion loadings, contrary to those from the sea. The ranges of wind speed, wind direction and temperature corresponding to the maximum total ion concentration (TIC) were 3.5-4 m s-1, 79°-90° and 21°C-22°C, respectively. In view of the low correlation coefficients, a new parameter Lr was proposed as a predictive parameter for TIC and the correlation coefficient increased to 0.74. Based on aerosol concentrations during the sea-fog cases in 2010, we confirmed that fog-water chemical composition also depended on the species and sizes of aerosol particles. When a dust storm passed through Donghai Island, the number concentration of large aerosol particles (with diameter > 1 μm) increased. This caused the ratio of Ca2+/Na+ in fog-water to increase significantly.

  6. Acute toxicity of smoke screen materials to aquatic organisms, white phosphorus-felt, red phosphorus-butyl rubber and SGF No. 2 fog oil. Final report

    SciTech Connect

    Poston, T.M.; McFadden, K.M.; Bean, R.M.; Clark, M.L.; Thomas, B.L.; Killand, B.W.; Prohammer, L.A.; Kalkwarf, D.R.

    1986-04-01

    The acute toxicity of three obscurants was determined for nine freshwater organisms. The materials tested were white phosphorus-felt smoke, red phosphorus-butyl rubber (RP-BR) smoke, and smoke generator fuel (SGF) No. 2 fog oil (bulk and vaporized). The chemistry of WP-F and RP-BR smoke in water and the resulting effects on aquatic organisms are similar. Combustion of these two obscurants and their deposition in water leads to the formation of many complex oxy-phosphoric acids. Rates of hydrolysis of these complex products to ortho-phosphate were inconsistent and unpredictable over time. These products acidify water and produce toxic effects after exhausting the buffering capacity of the water. Acute 96 hr tests using Daphnia magna with neutralized and nonneutralized exposure solutions indicated that the presence of unidentified toxic component(s) acted independently of pH. At pH levels of 6.0 to 7.0, phosphorus combustion products precipitated out of solution leading to a bimodal toxic response in extended 96-hr tests with Daphnia magna. Most components of fog oil had low solubility in water. Saturation was apparent at approximately 0.1 to 0.3 mg/L total oil. Vaporization had no demonstrable effect on the chemistry or toxicity of the fog oil. Neither the bulk fog oil nor the vaporized fog oil was acutely toxic to freshwater animals at concentrations less than 10 mg/L total oil. In oil-water mixes in excess of 1.0 mg/L total oil, fog oil quickly separated and floated to the surface. The primary hazard associated with vaporized and bulk fog oil was the physical effect of oil fouling the organisms. Photolysis increased the concentration of water-soluble components of the fog oil. Acute toxicity was demonstrated in oil-water mixes (approx.10 mg/L total oil) of photolyzed bulk and vaporized fog oil. No difference in toxicity was observed between photolyzed and non-photolyzed dilutions of OWM at comparable levels of total oil.

  7. Discrimination of ionic pollutants except condensation nuclei of acid fog using an ultrasonic humidifier.

    PubMed

    Yoshimura, Keiji; Kikuchi, Ryoei; Kimoto, Takashi; Ozeki, Toru; Imano, Kazuhiko; Kajikawa, Masahiro; Ogawa, Nobuaki

    2006-06-01

    Fog droplets in the atmosphere are first produced by the activation of cloud condensation nuclei (CCN), which are originally some ionic compound. Subsequently, the nuclei grow by vapor diffusion. Fog droplets are polluted through the activation process and successive diffusion growth and residence (post activation). We cannot distinguish the effects of the two pollution processes of natural fog water samples. We found that fog droplets can be produced artificially without CCN using an ultrasonic humidifier. Because the artificial fog droplets are not polluted by CCN, the movement of the fog droplets in natural air will take up some pollutants in the air. Consequently, the two pollution processes of fog (the activation of CCN and the post activation process) can be discriminated using data from field experiments. This sampling analytical method is extremely important for further research regarding fog, clouds and environmental chemistry.

  8. Mercury in fog on the Bay of Fundy (Canada)

    NASA Astrophysics Data System (ADS)

    Ritchie, Charles D.; Richards, William; Arp, Paul A.

    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.

  9. Effects of acid fog and ozone on conifers. Final report

    SciTech Connect

    Bytnerowicz, A.; Olszyk, D.M.; Takemoto, B.K.; McCool, P.M.; Musselman, R.C.

    1989-05-01

    This study evaluated the effects of acidic fog (pH 2.0, 3.0, or 4.0) on the physiological, biochemical, and growth responses of two coniferous tree species (Pinus ponderosa and Abies concolor), and determined if exposure to acidic fog predisposed the tree seedlings to the phytotoxic effects of ozone (O{sub 3}). Results provide evidence that the growth and metabolic responses of two coniferous tree species could be altered by multiple applications of acidic fog, and by exposure to ambient O{sub 3}. In general, the alterations were slight to modest, which may be attributed to the low degree of stress severity, and the slow rate of tree growth. The findings indicate that exposure to acidic fog followed by O{sub 3} does not cause detectable changes in conifer seedling growth within a single-growing season. Nevertheless, it is clear that acidic fog and O{sub 3} cause temporal alterations in seedling physiology and biochemistry.

  10. Relation Between Fog & Summer Stream Flow on the North Coast of California in Redwood National Park

    NASA Astrophysics Data System (ADS)

    Lavery, K.

    2012-12-01

    There are three common definitions of fog; visibility less than 800 meters (Dawson 1998), ceiling height less than 400 meters (Liepper 1995, Johnstone & Dawson 2010) or low level stratus that touches the ground. Regardless of the definition used the ecological importance of fog is evidenced by the commonly used term occult precipitation i.e. water that is not accounted for. Fog is most common on the coast of Northern California during summer, the time of least precipitation. The diurnal flux in stream flows is also most evident in the summer. Diurnal flux and seasonal trends in stream flow are thought to be controlled by precipitation and evapotranspiration. Fog impacts both precipitation and evapotranspiration. While changes in fog regimes are expected to occur as a result of climate change, the ability to measure fog and anticipate the implications are in nascent stages. Although, methods for detecting fog using satellite imagery have been developed they have not been perfected and they generally only give height info for the cloud deck (top of clouds). Although deck height is important for aviation and enables some inference of what is occurring on the ground the thickness and base height are important variables for developing a greater understanding of the impacts of fog. Fog harps will be used to detect fog on the ground. Fog harp data will be compared with the results of satellite imagery analysis for presence or absence of fog. After detrending, stream flow data will be divided into categories of fog and no fog. The two categories will be tested for a statistically significant difference. The results have the potential to help solve a piece of the climate change puzzle. The data will help with the anticipation of change in stream flows in areas with high levels of summer fog and Mediterranean climates as well as refine techniques for analyzing satellite imagery for presence or absence of fog.

  11. The pioneer study of fog detection and horizontal precipitation measurement at subtropical highland of Taiwan

    NASA Astrophysics Data System (ADS)

    Lin, P. H.; Lai, K. L.

    2010-07-01

    Heavy rainfall in highland caused by the interaction of tropical storms and sharp terrain is one of the major natural disasters in Taiwan. But there is no quantitative measurement on the fog and its horizontal precipitation (HP) to estimate the storage of water by plants in the highland region of Taiwan. In this pioneer study, we studied the fog detection and its horizontal precipitation amount, existence length and monthly variation at Kuan-Wu recreation area in Shei-Pa National Park of Taiwan. The 20-year (1988~2007) record length of meteorological data at Kuan-Wu was analyzed first to build up the background information of the local weather. The FDID (fog detection and interception device) including two fog detectors, two fog collectors and auto-shooting digital camera was delivered in this field program. The parallel experiment indoor with a fog tunnel also confirms the performance of polypropylene net used in FDID. FDID has collected data in the field over one year, and the preliminary results show that some components of FDID present the capability of fog event detection and give quantitative data of fog interception. The digital images in 5-min interval via fog collector data detected over 90% happening of fog event in the data available days. Through the RGB diagnosis in different pixel domains (different distances to the camera) on the digital images, the fog events are distinguished into light, medium and heavy fog events. The characteristics of daily and monthly variations of fog events could be explained through the terrain and local climate effects well. We also found the horizontal precipitation from fog provides ~11% extra water amount in the no-rain days. The happened possibility of fog & stratus cloud with The MTSAT geostationary IR channels by Central Weather Bureau is also validated by the FDID in-situ measurement. It shows that the remote sensing product of fog detection in nighttime has good correlation with FDID ground measurement.

  12. A review of observations of organic matter in fogs and clouds: Origin, processing and fate

    NASA Astrophysics Data System (ADS)

    Herckes, Pierre; Valsaraj, Kalliat T.; Collett, Jeffrey L.

    2013-10-01

    While fog and cloud composition has been studied for decades, most of the research was limited to inorganic species and fog acidity. Recently the focus has shifted towards organic matter in the atmospheric aqueous phase of fogs and clouds: its origin, reactivity and fate. An impressive number of fog and cloud chemistry observational studies have been performed over the last decade throughout the world. In the present work we will review the state of knowledge of atmospheric organic matter processing by fogs, with a focus on field observations. We start by reviewing observational studies in general and then discuss our knowledge on the occurrence of organic matter in fogs, its solubility, characterization and molecular speciation. Organic carbon concentrations can vary widely from approximately 1 mg C/L in remote marine environments to more than 100 mg C/L in polluted radiation fogs, accounting for a substantial part of fogwater solutes. The carbonaceous material can enter the droplets from the gas and particle phase and the scavenging behavior of fogs will be detailed. Observational studies showed evidence of aqueous phase transformation of organic material, in particular secondary organic aerosol (SOA) generation, in fog. Recent observations of biological material in fog suggest also an impact of biological processing within the droplets on fog organic matter. The review will end with a discussion of the impact of fog on the deposition fluxes of organic material and hence its atmospheric lifetime.

  13. 49 CFR 393.24 - Requirements for head lamps, auxiliary driving lamps and front fog lamps.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... lamps and front fog lamps. 393.24 Section 393.24 Transportation Other Regulations Relating to... Devices, and Electrical Wiring § 393.24 Requirements for head lamps, auxiliary driving lamps and front fog.... 108. Auxiliary driving lamps and/or front fog lamps may not be used to satisfy the requirements...

  14. 49 CFR 393.24 - Requirements for head lamps, auxiliary driving lamps and front fog lamps.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... lamps and front fog lamps. 393.24 Section 393.24 Transportation Other Regulations Relating to... Devices, and Electrical Wiring § 393.24 Requirements for head lamps, auxiliary driving lamps and front fog.... 108. Auxiliary driving lamps and/or front fog lamps may not be used to satisfy the requirements...

  15. 49 CFR 393.24 - Requirements for head lamps, auxiliary driving lamps and front fog lamps.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... lamps and front fog lamps. 393.24 Section 393.24 Transportation Other Regulations Relating to... Devices, and Electrical Wiring § 393.24 Requirements for head lamps, auxiliary driving lamps and front fog.... 108. Auxiliary driving lamps and/or front fog lamps may not be used to satisfy the requirements...

  16. Spray characterization of thermal fogging equipment typically used in vector control

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The generation of insecticide laden fogs provides an effective method for controlling flying insects. One of the critical factors affecting the effectiveness of a thermal fogging application is the generation of droplets that will remain aloft in the fogging cloud and moves into the area where the ...

  17. A Molecular Explanation of How the Fog Is Produced When Dry Ice Is Placed in Water

    ERIC Educational Resources Information Center

    Kuntzleman, Thomas S.; Ford, Nathan; No, Jin-Hwan; Ott, Mark E.

    2015-01-01

    Everyone enjoys seeing the cloudy white fog generated when solid carbon dioxide (dry ice) is placed in water. Have you ever wondered what physical and chemical processes occur to produce this fog? When asked this question, many chemical educators suggest that the fog is produced when atmospheric water vapor condenses on cold carbon dioxide gas…

  18. Monte Carlo simulation of laser attenuation characteristics in fog

    NASA Astrophysics Data System (ADS)

    Wang, Hong-Xia; Sun, Chao; Zhu, You-zhang; Sun, Hong-hui; Li, Pan-shi

    2011-06-01

    Based on the Mie scattering theory and the gamma size distribution model, the scattering extinction parameter of spherical fog-drop is calculated. For the transmission attenuation of the laser in the fog, a Monte Carlo simulation model is established, and the impact of attenuation ratio on visibility and field angle is computed and analysed using the program developed by MATLAB language. The results of the Monte Carlo method in this paper are compared with the results of single scattering method. The results show that the influence of multiple scattering need to be considered when the visibility is low, and single scattering calculations have larger errors. The phenomenon of multiple scattering can be interpreted more better when the Monte Carlo is used to calculate the attenuation ratio of the laser transmitting in the fog.

  19. Salt Fog Testing Iron-Based Amorphous Alloys

    SciTech Connect

    Rebak, Raul B.; Aprigliano, Louis F.; Day, S. Daniel; Farmer, Joseph C.

    2007-07-01

    Iron-based amorphous alloys are hard and highly corrosion resistant, which make them desirable for salt water and other applications. These alloys can be produced as powder and can be deposited as coatings on any surface that needs to be protected from the environment. It was of interest to examine the behavior of these amorphous alloys in the standard salt-fog testing ASTM B 117. Three different amorphous coating compositions were deposited on 316L SS coupons and exposed for many cycles of the salt fog test. Other common engineering alloys such as 1018 carbon steel, 316L SS and Hastelloy C-22 were also tested together with the amorphous coatings. Results show that amorphous coatings are resistant to rusting in salt fog. Partial devitrification may be responsible for isolated rust spots in one of the coatings. (authors)

  20. Clearing the Cosmic Fog - The Most Distant Galaxy Ever Measured

    NASA Astrophysics Data System (ADS)

    2010-10-01

    would not have been able to detect it", explains co-author Mark Swinbank (Durham University). Co-author Jean-Gabriel Cuby (Laboratoire d'Astrophysique de Marseille) remarks: "Studying the era of reionisation and galaxy formation is pushing the capability of current telescopes and instruments to the limit, but this is just the type of science that will be routine when ESO's European Extremely Large Telescope - which will be the biggest optical and near infrared telescope in the world - becomes operational." Notes [1] An earlier ESO result (eso0405) reported an object at a larger distance (a redshift of 10). However, further work failed to find an object of similar brightness at this position, and more recent observations with the NASA/Hubble Space Telescope have been inconclusive. The identification of this object with a galaxy at very high redshift is no longer considered to be valid by most astronomers. [2] When the Universe cooled down after the Big Bang, about 13.7 billion years ago, electrons and protons combined to form hydrogen gas. This cool dark gas was the main constituent of the Universe during the so-called Dark Ages, when there were no luminous objects. This phase eventually ended when the first stars formed and their intense ultraviolet radiation slowly made the hydrogen fog transparent again by splitting the hydrogen atoms back into electrons and protons, a process known as reionisation. This epoch in the Universe's early history lasted from about 150 million to 800 million years after the Big Bang. Understanding how reionisation happened and how the first galaxies formed and evolved is one of the major challenges of modern cosmology. [3] These Hubble observations are described at: http://www.spacetelescope.org/news/heic1001/ [4] Astronomers have two main ways of finding and measuring the distances to the earliest galaxies. They can take very deep images through differently coloured filters and measure the brightness of many objects at different

  1. Scavenging of urban air emissions by Fog at Delhi, India

    NASA Astrophysics Data System (ADS)

    Saxena, P.; Kulshrestha, U. C.

    2015-12-01

    The present study focuses upon the understanding of fog water chemistry in Delhi city. Total seventy fog water samples were collected at two different sites in Delhi during December 2014 to March 2015. Selected parameters such as pH, major anions (Cl-, F-, NO3- and SO42-) and major cations (NH4+, K+, Ca2+, Mg2+, Na+) were determined in the samples. The pH of the fog water collected during the monitoring period at Site I (traffic intersection) varied from 4.68 to 5.58 indicating the acidic nature of fog water while at the site II (green cover area), it ranged from 6.11 to 6.88 having slightly lower acidity. At the Site I, the average concentration of Cl-, Na+, SO42-, NH4+ was recorded as 1.5 X 10-2, 8 X 10-3, 4 X 10-3 and 1 X 10-2 μEqu/L respectively. Such values of ionic species may be attributed to the local sources, including factories, motor vehicle emissions and civil construction etc. However, non-local sources such as moderate- and long-range transport of sea salt also had significant influence on ionic content of fog water. In general the Na+ ratio values were found to be higher side suggesting the influence of non-marine sources. Extremely high values of Cl-/ Na+ ratios indicated the contribution from combustion of organochlorine compounds. Hence, the higher ratios of inorganic ions and acidic pH revealed that fog is an effective mechanism for the scavenging of various pollutants emitted by different sources in the city.

  2. Acute exposure to acid fog. Effects on mucociliary clearance

    SciTech Connect

    Laube, B.L.; Bowes, S.M. III; Links, J.M.; Thomas, K.K.; Frank, R. )

    1993-05-01

    Submicrometric sulfuric acid (H2SO4) aerosol can affect mucociliary clearance without eliciting irritative symptoms or changes in pulmonary function. The effect of larger fog droplets containing H2SO4 on mucociliary clearance is unknown. We quantified mucociliary clearance from the trachea (n = 4) and small airways (n = 7) of young healthy male adults after an acute exposure to H2SO4 fog (MMAD = 10.3 microns; pH = 2.0; liquid water content = 481 +/- 65 mg/m3; osmolarity = 30 mOsm). Acid fog (AF) or saline fog (SF) (10.9 microns; 492 +/- 116 mg/m3; 30 mOsm) was administered for 40 min of unencumbered breathing (no mouth-piece) at rest and for 20 min of exercise sufficient to produce oronasal breathing. Fog exposures were followed by a methacholine (MCh) challenge (a measure of airway reactivity) or inhalation of technetium-99M radioaerosol (MMAD = 3.4 microns) on 2 study days each. Changes in symptoms and forced ventilatory function were also assessed. Clearance was quantified from computer-assisted analyses of gamma camera images of the lower respiratory tract in terms of %removal/min of the radiolabel from the trachea 25 min after inhalation and from the outer zone of the right lung after 1.9 to 3 h. Symptoms, forced ventilatory function, and MCh response were unaffected by either fog. Tracheal clearance was more rapid in four of four subjects after AF (0.83 +/- 1.58% removal/min) compared with that after SF (-0.54 +/- 0.85% removal/min). Outer zone clearance was more rapid in six of seven subjects after AF (0.22 +/- 0.15% removal/min) compared with that after SF (0.01 +/- 0.09% removal/min).

  3. Fog water collection measurements along the Central California Coast

    NASA Astrophysics Data System (ADS)

    Fernandez, D. M.; Hiatt, C.; Potter, C. S.

    2012-12-01

    For the past several years a number of standard fog collectors (SFC's) have been deployed at various locations in the Monterey Bay region to assess the volume and variation of Monterey area fog water deposition. SFC's contain a square meter of double thickness 50% shade Coresa mesh and are mounted with their base at a height of 2.0 meters. Each SFC is fitted with a tipping bucket rain gauge so as to accurately measure the water intercepted by each instrument. Collection of water deposition from each SFC provides a quantitative means to detect and measure the presence of ground fog and, coupled with vegetation type, to estimate the associated moisture flux to the soil. Since summer 2009, three SFC's have been deployed at locations near CSU Monterey Bay in the towns of Marina and Seaside and 3 others were deployed along an elevation gradient in the Big Sur region. The volume of water collected from each instrument is recorded at 15-minute intervals. Despite spacing of only 1-5 km between correspondent SFC's at a given location, we observe significant variations in the presence of and characteristics of coincident fog events. This presentation examines totals of fog water collected over the time period (which spans from July 2009 through 2012) as well as local gradients and diurnal and seasonal variations based upon the limited sample size. In addition, this presentation will explore the interdisciplinary connections to other regional research projects, including lizard species extinctions, assessment of the physical effects of climate change on fog, and mercury cycling.

  4. Forest Restoration in a Fog Oasis: Evidence Indicates Need for Cultural Awareness in Constructing the Reference

    PubMed Central

    Balaguer, Luís; Arroyo-García, Rosa; Jiménez, Percy; Jiménez, María Dolores; Villegas, Luís; Cordero, Irene; Rubio de Casas, Rafael; Fernández-Delgado, Raúl; Ron, María Eugenia; Manrique, Esteban; Vargas, Pablo; Cano, Emilio; Pueyo, José J.; Aronson, James

    2011-01-01

    Background In the Peruvian Coastal Desert, an archipelago of fog oases, locally called lomas, are centers of biodiversity and of past human activity. Fog interception by a tree canopy, dominated by the legume tree tara (Caesalpinia spinosa), enables the occurrence in the Atiquipa lomas (southern Peru) of an environmental island with a diverse flora and high productivity. Although this forest provides essential services to the local population, it has suffered 90% anthropogenic reduction in area. Restoration efforts are now getting under way, including discussion as to the most appropriate reference ecosystem to use. Methodology/Principal Findings Genetic diversity of tara was studied in the Atiquipa population and over a wide geographical and ecological range. Neither exclusive plastid haplotypes to loma formations nor clear geographical structuring of the genetic diversity was found. Photosynthetic performance and growth of seedlings naturally recruited in remnant patches of loma forest were compared with those of seedlings recruited or planted in the adjacent deforested area. Despite the greater water and nitrogen availability under tree canopy, growth of forest seedlings did not differ from that of those recruited into the deforested area, and was lower than that of planted seedlings. Tara seedlings exhibited tight stomatal control of photosynthesis, and a structural photoprotection by leaflet closure. These drought-avoiding mechanisms did not optimize seedling performance under the conditions produced by forest interception of fog moisture. Conclusions/Significance Both weak geographic partitioning of genetic variation and lack of physiological specialization of seedlings to the forest water regime strongly suggest that tara was introduced to lomas by humans. Therefore, the most diverse fragment of lomas is the result of landscape management and resource use by pre-Columbian cultures. We argue that an appropriate reference ecosystem for ecological restoration

  5. Radiation fog chemical composition and its temporal trend over an eight year period

    NASA Astrophysics Data System (ADS)

    Straub, Derek J.

    2017-01-01

    Radiation fog samples have been collected at a rural site in Central Pennsylvania from 2007 through 2015 in order to document chemical composition, assess concentration changes over time, and to provide insight into emission sources that influence the region. The collection of samples over multiple years makes this one of the few long duration radiation fog studies that have been completed. During the course of the campaign, 146 samples were obtained and analyzed for pH, major inorganic ions, low molecular weight organic acids, total organic carbon (TOC) and total nitrogen (TN). Ammonium (median concentration = 209 μN), sulfate (69 μN), calcium (51 μN), and nitrate (31 μN) were the most abundant inorganic ions, although these were present at much lower concentrations than for radiation fog studies conducted in other locations. Organic acids, of which formate (20 μM) and acetate (21 μM) were the most abundant, were closer in magnitude to measurements made during previous studies. Organic acids accounted for 15% of TOC, which had a median concentration of 6.6 mgC l-1. The median concentration of TN was 3.6 mgN l-1, 18% of which was determined to be organic nitrogen. Statistically significant decreasing trends from 2007 to 2015 were noted for sulfate, ammonium, chloride, and nitrate. For the same period, an increase in pH was observed. Seasonal trends were identified for a number of species as well. The partitioning of ammonia between the gas and aqueous phases was also investigated and found to deviate significantly from equilibrium.

  6. Secondary Organic Aerosol Produced from Aqueous Reactions of Phenols in Fog Drops and Deliquesced Particles

    NASA Astrophysics Data System (ADS)

    Smith, J.; Anastasio, C.

    2014-12-01

    The formation and evolution of secondary organic aerosol (SOA) in atmospheric condensed phases (i.e., aqueous SOA) can proceed rapidly, but relatively little is known of the important aqueous SOA precursors or their reaction pathways. In our work we are studying the aqueous SOA formed from reactions of phenols (phenol, guaiacol, and syringol), benzene-diols (catechol, resorcinol, and hydroquinone), and phenolic carbonyls (e.g., vanillin and syringaldehyde). These species are potentially important aqueous SOA precursors because they are released in large quantities from biomass burning, have high Henry's Law constants (KH = 103 -109 M-1 atm-1) and are rapidly oxidized. To evaluate the importance of aqueous reactions of phenols as a source of SOA, we first quantified the kinetics and SOA mass yields for 11 phenols reacting via direct photodegradation, hydroxyl radical (•OH), and with an excited organic triplet state (3C*). In the second step, which is the focus of this work, we use these laboratory results in a simple model of fog chemistry using conditions during a previously reported heavy biomass burning event in Bakersfield, CA. Our calculations indicate that under aqueous aerosol conditions (i.e., a liquid water content of 100 μg m-3) the rate of aqueous SOA production (RSOA(aq)) from phenols is similar to the rate in the gas phase. In contrast, under fog/cloud conditions the aqueous RSOA from phenols is 10 times higher than the rate in the gas phase. In both of these cases aqueous RSOA is dominated by the oxidation of phenols by 3C*, followed by direct photodegradation of phenolic carbonyls, and then •OH oxidation. Our results suggest that aqueous oxidation of phenols is a significant source of SOA during fog events and also during times when deliquesced aerosols are present.

  7. Advecting Procedural Textures for 2D Flow Animation

    NASA Technical Reports Server (NTRS)

    Kao, David; Pang, Alex; Moran, Pat (Technical Monitor)

    2001-01-01

    This paper proposes the use of specially generated 3D procedural textures for visualizing steady state 2D flow fields. We use the flow field to advect and animate the texture over time. However, using standard texture advection techniques and arbitrary textures will introduce some undesirable effects such as: (a) expanding texture from a critical source point, (b) streaking pattern from the boundary of the flowfield, (c) crowding of advected textures near an attracting spiral or sink, and (d) absent or lack of textures in some regions of the flow. This paper proposes a number of strategies to solve these problems. We demonstrate how the technique works using both synthetic data and computational fluid dynamics data.

  8. Concentration polarization, surface currents, and bulk advection in a microchannel

    NASA Astrophysics Data System (ADS)

    Nielsen, Christoffer P.; Bruus, Henrik

    2014-10-01

    We present a comprehensive analysis of salt transport and overlimiting currents in a microchannel during concentration polarization. We have carried out full numerical simulations of the coupled Poisson-Nernst-Planck-Stokes problem governing the transport and rationalized the behavior of the system. A remarkable outcome of the investigations is the discovery of strong couplings between bulk advection and the surface current; without a surface current, bulk advection is strongly suppressed. The numerical simulations are supplemented by analytical models valid in the long channel limit as well as in the limit of negligible surface charge. By including the effects of diffusion and advection in the diffuse part of the electric double layers, we extend a recently published analytical model of overlimiting current due to surface conduction.

  9. Catheter for Cleaning Surgical Optics During Surgical Procedures: A Possible Solution for Residue Buildup and Fogging in Video Surgery.

    PubMed

    de Abreu, Igor Renato Louro Bruno; Abrão, Fernando Conrado; Silva, Alessandra Rodrigues; Corrêa, Larissa Teresa Cirera; Younes, Riad Nain

    2015-05-01

    Currently, there is a tendency to perform surgical procedures via laparoscopic or thoracoscopic access. However, even with the impressive technological advancement in surgical materials, such as improvement in quality of monitors, light sources, and optical fibers, surgeons have to face simple problems that can greatly hinder surgery by video. One is the formation of "fog" or residue buildup on the lens, causing decreased visibility. Intracavitary techniques for cleaning surgical optics and preventing fog formation have been described; however, some of these techniques employ the use of expensive and complex devices designed solely for this purpose. Moreover, these techniques allow the cleaning of surgical optics when they becomes dirty, which does not prevent the accumulation of residue in the optics. To solve this problem we have designed a device that allows cleaning the optics with no surgical stops and prevents the fogging and residue accumulation. The objective of this study is to evaluate through experimental testing the effectiveness of a simple device that prevents the accumulation of residue and fogging of optics used in surgical procedures performed through thoracoscopic or laparoscopic access. Ex-vivo experiments were performed simulating the conditions of residue presence in surgical optics during a video surgery. The experiment consists in immersing the optics and catheter set connected to the IV line with crystalloid solution in three types of materials: blood, blood plus fat solution, and 200 mL of distilled water and 1 vial of methylene blue. The optics coupled to the device were immersed in 200 mL of each type of residue, repeating each immersion 10 times for each distinct residue for both thirty and zero degrees optics, totaling 420 experiments. A success rate of 98.1% was observed after the experiments, in these cases the device was able to clean and prevent the residue accumulation in the optics.

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

    NASA Astrophysics Data System (ADS)

    Chang, Shih-Chieh; Lai, I.-Ling; Wu, Jiunn-Tzong

    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 H 2O 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.

  11. The Climatology, Frequency, and Distribution of Cold Season Fog Events in Northern Utah

    NASA Astrophysics Data System (ADS)

    Hodges, Derek; Pu, Zhaoxia

    2016-09-01

    The distribution and frequency of fog events during the cold season in northern Utah is studied using surface Mesowest data from 2004 to 2014. Fog is identified using the reported weather conditions, relative humidity, and visibility. The length and time of each fog occurrence is calculated. Statistics are performed on daily, monthly, and seasonal timescales. To ensure representativeness of the data and to account for the relatively small sample size, "near-fog" conditions are included in some statistics. Results show that there is significant variability among the valleys in northern Utah in terms of both quantity and timing of fog events. Fog occurs more frequently in locations close to lakes such as the Great Salt Lake or Utah Lake than in locations farther away. It is also noted that small, enclosed valleys have higher amounts of fog than broader, open valleys. Throughout the region, there is a distinct peak in fog in late January for most stations. A strong peak in fog occurrences near dawn is also found for all cold season months. In addition, the influence of local, mesoscale conditions on the fog distribution is evident in many stations. It is found that the existence of fog at one location is a very poor predictor of fog at nearby locations on a daily timescale, which implies serious forecasting difficulties over complex terrain. However, it is also found that on an annual timescale the amount of fog at one location can be used to estimate the amount of fog at another location. The controlling factors that contribute to the variability of fog events over northern Utah (a mountainous region) are discussed.

  12. Optimal Stretching in Advection-Reaction-Diffusion Systems

    NASA Astrophysics Data System (ADS)

    Nevins, Thomas D.; Kelley, Douglas H.

    2016-10-01

    We investigate growth of the excitable Belousov-Zhabotinsky reaction in chaotic, time-varying flows. In slow flows, reacted regions tend to lie near vortex edges, whereas fast flows restrict reacted regions to vortex cores. We show that reacted regions travel toward vortex centers faster as flow speed increases, but nonreactive scalars do not. For either slow or fast flows, reaction is promoted by the same optimal range of the local advective stretching, but stronger stretching causes reaction blowout and can hinder reaction from spreading. We hypothesize that optimal stretching and blowout occur in many advection-diffusion-reaction systems, perhaps creating ecological niches for phytoplankton in the ocean.

  13. Optimal Stretching in Advection-Reaction-Diffusion Systems.

    PubMed

    Nevins, Thomas D; Kelley, Douglas H

    2016-10-14

    We investigate growth of the excitable Belousov-Zhabotinsky reaction in chaotic, time-varying flows. In slow flows, reacted regions tend to lie near vortex edges, whereas fast flows restrict reacted regions to vortex cores. We show that reacted regions travel toward vortex centers faster as flow speed increases, but nonreactive scalars do not. For either slow or fast flows, reaction is promoted by the same optimal range of the local advective stretching, but stronger stretching causes reaction blowout and can hinder reaction from spreading. We hypothesize that optimal stretching and blowout occur in many advection-diffusion-reaction systems, perhaps creating ecological niches for phytoplankton in the ocean.

  14. Jet Magnetically Accelerated from Advection Dominated Accretion Flow

    NASA Astrophysics Data System (ADS)

    Gong, Xiao-Long; Jiang, Zhi-Xiong

    2014-08-01

    A jet model for the jet power arising from a steady, optically thin, advection dominated accretion flow (ADAF) around a Kerr black hole (BH) is proposed. We investigate the typical numerical solutions of ADAF, and calculate the jet power from an ADAF using a general relativistic version of electronic circuit theory. It is shown that the jet power concentrates in the inner region of the accretion flow, and the higher the degree to which the flow advection-dominated is, the lower the jet power from the ADAF is.

  15. Fast multigrid solution of the advection problem with closed characteristics

    SciTech Connect

    Yavneh, I.; Venner, C.H.; Brandt, A.

    1996-12-31

    The numerical solution of the advection-diffusion problem in the inviscid limit with closed characteristics is studied as a prelude to an efficient high Reynolds-number flow solver. It is demonstrated by a heuristic analysis and numerical calculations that using upstream discretization with downstream relaxation-ordering and appropriate residual weighting in a simple multigrid V cycle produces an efficient solution process. We also derive upstream finite-difference approximations to the advection operator, whose truncation terms approximate {open_quotes}physical{close_quotes} (Laplacian) viscosity, thus avoiding spurious solutions to the homogeneous problem when the artificial diffusivity dominates the physical viscosity.

  16. Clay with Desiccation Cracks is an Advection Dominated Environment

    NASA Astrophysics Data System (ADS)

    Baram, S.; Kurtzman, D.; Sher, Y.; Ronen, Z.; Dahan, O.

    2012-04-01

    , indicating deep soil evaporation. Daily fluctuation of the air temperature in the desiccation cracks supported thermally induced air convection within the cracks void and could explain the deep soil salinization process. Combination of all the abovementioned observations demonstrated that the formation of desiccation cracks network in dispersive clay sediments generates a bulk advection dominated environment for both air and water flow, and that the reference to clay sediments as "hydrologically safe" should to be reconsidered.

  17. [Multiple scattering of visible and infrared light by sea fog over wind driving rough sea surface].

    PubMed

    Sun, Xian-Ming; Wang, Hai-Hua; Lei, Cheng-Xin; Shen, Jin

    2013-08-01

    The present paper is concerned with computing the multiple scattering characteristics of a sea fog-sea surface couple system within this context. The single scattering characteristics of sea fog were studied by Mie theory, and the multiple scattering of sunlight by single sea fog layer was studied by radiative transfer theory. The reflection function of a statistically rough ocean surface was obtained using the standard Kirchhoff formulation, with shadowing effects taken into account. The reflection properties of the combined sea fog and ocean surface were obtained employing the adding method, and the results indicated that the reflected light intensity of sea fog increased with the sea background.

  18. The theoretical analysis of the Fog removal in the LNG Ambient Vaporizer

    NASA Astrophysics Data System (ADS)

    Lee, T.; Lee, D.; Jeong, H.; Chung, H.

    2015-09-01

    The fog removal process is one of the important process in LNG Ambient Vaporizer. In this study we carried out theoretical study of the fog removal process in LNG Ambient Vaporizer. The LNG Ambient Vaporizer in Incheon area was used in our study. The fog temperature and the required energy produced from air fan to remove fog in LNG Ambient Vaporizer were calculated using average temperature of Incheon area in 2012 by Psychometruc Chart method. As a result we can be remove fog in LNG Ambient Vaporizer using Enthalpy[kW] energy in summer season and Enthalpy[kW] in winter season respectively.

  19. The Fiberoptle Guided Missile (FOG-M)

    NASA Astrophysics Data System (ADS)

    Jacobs, Paul L.

    1989-02-01

    The Fiberoptic Guided Missile (FOG-M) was developed in the U.S. Army's Research, Development, and Engineering Center (RDEC) as a demonstration system for killing armor in an infantry application. The RDEC design uses a television sensor in the nose of the missile for in-flight target acquisition, bringing the video signal down a fiberoptic link that pays out behind the missile as it flies, to a gunner securely hidden in a defiladed launch vehicle. The gunner is able to select the target on a video screen and lock on an autotracker or alternately manually track the target to impact. The system design would use a common warhead for either armor or helicopter targets. The system is currently mounted on the High Mobility, Multipurpose Wheeled Vehicle (HMMWV), containing the gunner's station, launcher, and flight missiles. The gunner's station includes the capability for detailed mission planning, digital map display based on the Defense Mapping Agency's digital map databases, and display of the air battle situation for the gunner. Automatic targeting, control of multiple missiles in the air simultaneously, navigation using a digital correlator, and autotracking of moving targets in cluttered backgrounds with gunner selectable offset tracking capability are also available. The system has a capability to train the gunner using a perspective view scene generator that mimics the video scene he would be presented during missile flight. The scene generator uses the same hardware that displays the digital map, while a simulation of the missile runs in one of the system's computer processors to accurately move the seeker presentation around the scene. All of the other hardware used in embedded training is the same as the actual firing hardware. The system concept has been chosen by the Army as the non-line-of-sight (NLOS) component of the Forward Area Air Defense System (FAADS). The initial design is being upgraded for the MIL SPEC environment to allow early operational

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

    NASA Astrophysics Data System (ADS)

    Colomb, M.; Hirech, K.; André, P.; Boreux, J. J.; Lacôte, P.; Dufour, J.

    2008-03-01

    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.

  1. Non-human primate FOG develops with advanced parkinsonism induced by MPTP Treatment.

    PubMed

    Revuelta, Gonzalo J; Uthayathas, Subramaniam; Wahlquist, Amy E; Factor, Stewart A; Papa, Stella M

    2012-10-01

    Freezing of gait (FOG) is a debilitating feature of Parkinson's disease (PD) and other forms of parkinsonism. The anatomical or pathophysiological correlates are poorly understood largely due to the lack of a well-established animal model. Here we studied whether FOG is reproduced in the non-human primate (NHP) model of PD. 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkeys (Genus Macaca, n=29) were examined for the development of FOG, and the leg movements were recorded with accelerometry. The relationships between developing FOG and the animals' characteristics, the MPTP treatments, and the modeled outcomes were determined. In parkinsonian monkeys FOG developed frequently (48%) manifesting similar characteristics to those seen in PD patients. In addition, FOG episodes in the monkey were accompanied by leg trembling with the typical duration (2-10s) and frequency (~7 Hz). The development of NHP FOG was significantly associated with the severity of parkinsonism, as shown by high motor disability scores (≥ 20) and levodopa-induced dyskinesia scores (p=0.01 and p=0.04, respectively). Differences in demographics and MPTP treatments (doses, treatment duration, etc.) had no influence on NHP FOG occurrence, with the exception of gender that showed FOG predominance in males (p=0.03). The unique features of FOG in PD can be replicated in severely parkinsonian macaques, and this represents the first description of a FOG animal model.

  2. Hierarchical Surface Architecture of Plants as an Inspiration for Biomimetic Fog Collectors.

    PubMed

    Azad, M A K; Barthlott, W; Koch, K

    2015-12-08

    Fog collectors can enable us to alleviate the water crisis in certain arid regions of the world. A continuous fog-collection cycle consisting of a persistent capture of fog droplets and their fast transport to the target is a prerequisite for developing an efficient fog collector. In regard to this topic, a biological superior design has been found in the hierarchical surface architecture of barley (Hordeum vulgare) awns. We demonstrate here the highly wettable (advancing contact angle 16° ± 2.7 and receding contact angle 9° ± 2.6) barbed (barb = conical structure) awn as a model to develop optimized fog collectors with a high fog-capturing capability, an effective water transport, and above all an efficient fog collection. We compare the fog-collection efficiency of the model sample with other plant samples naturally grown in foggy habitats that are supposed to be very efficient fog collectors. The model sample, consisting of dry hydrophilized awns (DH awns), is found to be about twice as efficient (fog-collection rate 563.7 ± 23.2 μg/cm(2) over 10 min) as any other samples investigated under controlled experimental conditions. Finally, a design based on the hierarchical surface architecture of the model sample is proposed for the development of optimized biomimetic fog collectors.

  3. Transcriptional cofactors of the FOG family interact with GATA proteins by means of multiple zinc fingers.

    PubMed Central

    Fox, A H; Liew, C; Holmes, M; Kowalski, K; Mackay, J; Crossley, M

    1999-01-01

    Friend of GATA-1 (FOG-1) is a zinc finger protein that has been shown to interact physically with the erythroid DNA-binding protein GATA-1 and modulate its transcriptional activity. Recently, two new members of the FOG family have been identified: a mammalian protein, FOG-2, that also associates with GATA-1 and other mammalian GATA factors; and U-shaped, a Drosophila protein that interacts with the Drosophila GATA protein Pannier. FOG proteins contain multiple zinc fingers and it has been shown previously that the sixth finger of FOG-1 interacts specifically with the N-finger but not the C-finger of GATA-1. Here we show that fingers 1, 5 and 9 of FOG-1 also interact with the N-finger of GATA-1 and that FOG-2 and U-shaped also contain multiple GATA-interacting fingers. We define the key contact residues and show that these residues are highly conserved in GATA-interacting fingers. We examine the effect of selectively mutating the four interacting fingers of FOG-1 and show that each contributes to FOG-1's ability to modulate GATA-1 activity. Finally, we show that FOG-1 can repress GATA-1-mediated activation and present evidence that this ability involves the recently described CtBP co-repressor proteins that recognize all known FOG proteins. PMID:10329627

  4. Hydrophobic/Hydrophilic Cooperative Janus System for Enhancement of Fog Collection.

    PubMed

    Cao, Moyuan; Xiao, Jiasheng; Yu, Cunming; Li, Kan; Jiang, Lei

    2015-09-09

    Harvesting micro-droplets from fog is a promising method for solving global freshwater crisis. Different types of fog collectors have been extensively reported during the last decade. The improvement of fog collection can be attributed to the immediate transportation of harvested water, the effective regeneration of the fog gathering surface, etc. Through learning from the nature's strategy for water preservation, the hydrophobic/hydrophilic cooperative Janus system that achieved reinforced fog collection ability is reported here. Directional delivery of the surface water, decreased re-evaporation rate of the harvested water, and thinner boundary layer of the collecting surface contribute to the enhancement of collection efficiency. Further designed cylinder Janus collector can facilely achieve a continuous process of efficient collection, directional transportation, and spontaneous preservation of fog water. This Janus fog harvesting system should improve the understanding of micro-droplet collection system and offer ideas to solve water resource crisis.

  5. Research and fabrication of integrated optical chip in FOG

    NASA Astrophysics Data System (ADS)

    En, De; Xu, Ke-xin; Chen, Cai-he; Cui, Yu-ming; Wang, Jin-wu; Zhao, Ya-bing; Si, Qin

    2009-05-01

    Fiber optic gyroscope is a completely static, pure optical gyroscope, with a high resolution and other advantages. In order to make the Fiber optic gyroscope be smaller in size, more reliable and sensitive, this paper presents a new type of interference integrated optical chip, which is X-cut and Y-propagation LiNbO3 substrate with the dimensions of 38mm×6mm× 2mm. We research and design Double-Y branching guide, phase modulator and polarizers of Integrated Optical Chip in FOG. Double-Y branching waveguide, phase modulator and polarizers were integrated in a chip, on which sensing element, resource (SLD), electrophotonic detector (PIN) and signal demodulation circuit are hybrid-Integrated together, then we get an acceleration FOG of high resolution. We test the chip with input light and find that diffraction image of output light from the double-Y branching waveguide is well symmetric, which indicates that the double-Y branching waveguide is 3dB beam-splitting, to overcome deficiencies of fiber coupler of splicing type and dual-melting conical. Exciting signal is coherent with the output signal of the FOG, and the performances of the FOG meets design requirement.

  6. Design of prototype charged particle fog dispersal unit

    NASA Technical Reports Server (NTRS)

    Collins, F. G.; Frost, W.; Kessel, P.

    1981-01-01

    The unit was designed to be easily modified so that certain features that influence the output current and particle size distribution could be examined. An experimental program was designed to measure the performance of the unit. The program described includes measurements in a fog chamber and in the field. Features of the nozzle and estimated nozzle characteristics are presented.

  7. 2. Fog signal house and light tower, view west southwest, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. Fog signal house and light tower, view west southwest, southeast and northeast sides of signal house, east and north sides of tower - Libby Island Light Station, At southern tip of Libby Island at entrance to Machias Bay, Machiasport, Washington County, ME

  8. 1. Light tower and fog signal house, view south southeast, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. Light tower and fog signal house, view south southeast, east and north sides of tower, northeast and northwest sides of signal house - Libby Island Light Station, At southern tip of Libby Island at entrance to Machias Bay, Machiasport, Washington County, ME

  9. Ecosystemic Complexity Theory of Conflict: Understanding the Fog of Conflict

    ERIC Educational Resources Information Center

    Brack, Greg; Lassiter, Pamela S.; Hill, Michele B.; Moore, Sarah A.

    2011-01-01

    Counselors often engage in conflict mediation in professional practice. A model for understanding the complex and subtle nature of conflict resolution is presented. The ecosystemic complexity theory of conflict is offered to assist practitioners in navigating the fog of conflict. Theoretical assumptions are discussed with implications for clinical…

  10. Effects of acid fog and dew on materials. Final report

    SciTech Connect

    Mansfeld, F.; Henry, R.; Vijayakumar, R.

    1989-10-01

    Field exposure tests have been carried out in order to separate the effects of acidic fog on materials damage from those caused by rain, dew and natural weathering. The test sites were McKittrick and Visalia in the Central Valley and West Casitas Pass in Ventura County. The field tests have been supported by laboratory tests in which materials damage has been determined during exposure to carefully controlled fog water chemistry. Analysis of the field exposure results for galvanized steel and the paint samples shows that the corrosivity of the atmosphere at the three test sites have been very low. The result is confirmed by the ACRM data which show very low corrosion activity. Since corrosion rates were so low approaching those for natural weathering, it was not possible to determine the effects of acidic fog. Based on the aerometric data and the observed corrosion behavior, it is doubtful that acidic fog conditions prevailed for significant times during the exposure period of 1/87 - 3/88 at Visalia and McKittrick. The results of the laboratory tests show that exposure to HNO3 at low pH and to high pollutant concentration increased the corrosion rate of galvanized steel to over 10 micro m/year. Exposure to HNO3 caused serious corrosion damage to anodized aluminum and the paint.

  11. DISCOVERY OF FOG AT THE SOUTH POLE OF TITAN

    SciTech Connect

    Brown, M. E.; Smith, A. L.; Chen, C.; Adamkovics, M.

    2009-11-20

    While Saturn's moon Titan appears to support an active methane hydrological cycle, no direct evidence for surface-atmosphere exchange has yet appeared. The indirect evidence, while compelling, could be misleading. It is possible, for example, that the identified lake features could be filled with ethane, an involatile long-term residue of atmospheric photolysis; the apparent stream and channel features could be ancient remnants of a previous climate; and the tropospheric methane clouds, while frequent, could cause no rain to reach the surface. We report here the detection of fog at the south pole of Titan during late summer using observations from the VIMS instrument on board the Cassini spacecraft. While terrestrial fog can form from a variety of causes, most of these processes are inoperable on Titan. Fog on Titan can only be caused by evaporation of nearly pure liquid methane; the detection of fog provides the first direct link between surface and atmospheric methane. Based on the detections presented here, liquid methane appears widespread at the south pole of Titan in late southern summer, and the hydrological cycle on Titan is currently active.

  12. Readability and Audience Response: Unfogging the Fog Indexes.

    ERIC Educational Resources Information Center

    Kent, Thomas L.

    Writers and writing teachers should be wary of depending on readability indexes as indicators of the difficulty of written messages. The Gunning Fog Index and the Damerst Clear Index, two readability formulas, were used to determine the readability of "A Statement of Editorial Policy" and two abstracts appearing in an issue of…

  13. Study on the FOG's signal based on wavelet

    NASA Astrophysics Data System (ADS)

    Tang, Ji-qiang; Fang, Jian-cheng; Zhang, Yan-shun

    2006-11-01

    In order to study on the fiber optical gyro (abbreviated as FOG) signal based on wavelet, this paper researches the FOG signal drift model and the properties of wavelet analyzed noise, introduces the wavelet filtering method, wavelet base selection, soft and hard threshold value de-noising algorithm and compulsive filtering based on The Haar wavelet. These threshold value filtering results of both of the soft and of the hard threshold value for the same wavelet base of db4 with the same Donoho threshold values and these results of compulsive filtering based on The Haar wavelet and db4 wavelet are presented also in this paper and then these main conclusions based on foregoing analysis are reached: Larger the resolving scale is, the filtering effect is more perfect. The soft threshold value filtering effect is better than that of the hard threshold value filtering at the cost of calculation when the threshold value is same. The zero shift of the compulsive filtering is least when both the wavelet and the resolving scale are same for these filtering methods. For the compulsive filtering with same wavelets, the filtering effect of Harr is better than that of db4 and the calculation of the former is fewer. Finally the author point out that applying the compulsive filtering with the Harr wavelet base and suitable resolving scale to the signal processing of FOG be helpful for the FOG's design and manufacturing.

  14. Real-time WAMI streaming target tracking in fog

    NASA Astrophysics Data System (ADS)

    Chen, Yu; Blasch, Erik; Chen, Ning; Deng, Anna; Ling, Haibin; Chen, Genshe

    2016-05-01

    Real-time information fusion based on WAMI (Wide-Area Motion Imagery), FMV (Full Motion Video), and Text data is highly desired for many mission critical emergency or security applications. Cloud Computing has been considered promising to achieve big data integration from multi-modal sources. In many mission critical tasks, however, powerful Cloud technology cannot satisfy the tight latency tolerance as the servers are allocated far from the sensing platform, actually there is no guaranteed connection in the emergency situations. Therefore, data processing, information fusion, and decision making are required to be executed on-site (i.e., near the data collection). Fog Computing, a recently proposed extension and complement for Cloud Computing, enables computing on-site without outsourcing jobs to a remote Cloud. In this work, we have investigated the feasibility of processing streaming WAMI in the Fog for real-time, online, uninterrupted target tracking. Using a single target tracking algorithm, we studied the performance of a Fog Computing prototype. The experimental results are very encouraging that validated the effectiveness of our Fog approach to achieve real-time frame rates.

  15. Invasions in heterogeneous habitats in the presence of advection.

    PubMed

    Vergni, Davide; Iannaccone, Sandro; Berti, Stefano; Cencini, Massimo

    2012-05-21

    We investigate invasions from a biological reservoir to an initially empty, heterogeneous habitat in the presence of advection. The habitat consists of a periodic alternation of favorable and unfavorable patches. In the latter the population dies at fixed rate. In the former it grows either with the logistic or with an Allee effect type dynamics, where the population has to overcome a threshold to grow. We study the conditions for successful invasions and the speed of the invasion process, which is numerically and analytically investigated in several limits. Generically advection enhances the downstream invasion speed but decreases the population size of the invading species, and can even inhibit the invasion process. Remarkably, however, the rate of population increase, which quantifies the invasion efficiency, is maximized by an optimal advection velocity. In models with Allee effect, differently from the logistic case, above a critical unfavorable patch size the population localizes in a favorable patch, being unable to invade the habitat. However, we show that advection, when intense enough, may activate the invasion process.

  16. Theory of advection-driven long range biotic transport

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We propose a simple mechanistic model to examine the effects of advective flow on the spread of fungal diseases spread by wind-blown spores. The model is defined by a set of two coupled non-linear partial differential equations for spore densities. One equation describes the long-distance advectiv...

  17. Black Hole Advective Accretion Disks with Optical Depth Transition

    SciTech Connect

    Artemove, Y.V.; Bisnovatyi-Kogan, G.S.; Igumenshchev, I.V.; Novikov, I.D.

    2006-02-01

    We have constructed numerically global solutions of advective accretion disks around black holes that describe a continuous transition between the effectively optically thick outer and optically thin inner disk regions. We have concentrated on models of accretion flows with large mass accretion rates, and we have employed a bridging formula for radiative losses at high and low effective optical depths.

  18. Observations of near-surface fog at the Phoenix Mars landing site

    NASA Astrophysics Data System (ADS)

    Moores, John E.; Komguem, Léonce; Whiteway, James A.; Lemmon, Mark T.; Dickinson, Cameron; Daerden, Frank

    2011-02-01

    The Surface Stereo Imager (SSI) on the Phoenix Mars Lander was able to complement the operations of the LIDAR on four occasions during the mission by observing the laser beam while the LIDAR laser was transmitting. These SSI observations permitted measurement of the scatter from atmospheric aerosols below 200 m where the LIDAR emitter and receiver do not overlap fully. The observed laser scattering was used to estimate the ice-water content (IWC) of near surface fog. Values of IWC up to 1.7 ± 1.0 mg m-3 were observed. Compared to air aloft, fog formation was inhibited near the surface which had accumulated at least 30 ± 24 mg m-2 (0.030 pr-μm) on sol 113. Microphysical modeling shows that when precipitation is included, up to 0.48 pr-μm of water may be present on the surface at the time of measurement. Integrated over the entire night, this represents up to 2.5 pr-μm of water taken up diurnally by the surface, or 6% of the total water column.

  19. Elimination of Laparoscopic Lens Fogging Using Directional Flow of CO2

    PubMed Central

    Redan, Jay A.

    2014-01-01

    Background and Objectives: Surgeons constantly struggle with the formation of condensation on the lens of a laparoscope, which prolongs procedures and reduces visibility of the abdominal cavity. The goal of this project was to build a device that would direct a flow of carbon dioxide (CO2) into an open chamber surrounding the lens of a laparoscope, acting to keep moisture away from the lens and eliminate condensation. Methods: The device isolates the lens of the laparoscope from the humid environment of the intraperitoneal cavity by creating a microenvironment of dry CO2. This was accomplished by building a communicating sleeve that created an open chamber around the distal 2 to 3 cm of the scope. Into this cavity, dry cool CO2 was pumped in from an insufflator so that the path of the gas would surround the lens of the scope and escape through a single outlet location through which the scope views the intraperitoneal cavity. This chamber is proposed to isolate the lens with a high percentage of dry CO2 and low humidity. The device was tested in 7 different adverse conditions that were meant to challenge the ability of the device to maintain the viewing field with no perceptible obstruction. Results: In all of the conditions tested, 25 trials total, the device successfully prevented and/or eliminated laparoscopic lens fogging. Conclusions: The device designed for this project points to the potential of a simple and effective mechanical method for eliminating laparoscopic lens fogging. PMID:24680144

  20. Advective velocity and energy dissipation rate in an oscillatory flow.

    PubMed

    Haider, Ziaul; Hondzo, Miki; Porte-Agel, Fernando

    2005-07-01

    Characterizing the transport processes at the sediment-water interface along sloping boundaries in lakes and reservoirs is of fundamental interest in lake and reservoir water quality management. The turbulent bottom boundary layer (TBBL) along a slope, induced by the breaking of internal waves in a linearly stratified fluid, was investigated through laboratory measurements. Fast response micro-scale conductivity and temperature probes in conjunction with laser-Doppler velocimetry were used to measure the time series of salinity, temperature, and velocity along a sloping boundary. Turbulent energy spectra were computed from the velocity data using a time-dependent advective velocity and Taylor's hypothesis. The energy spectra were used to estimate the energy dissipation rate at different positions in the TBBL. The advective velocity in this near-zero mean shear flow is based on an integral time scale (T(int)). The integral time scale is related to the average frequency of the spectral energy density of the flow velocity. The energy dissipation rate estimated from the variable advective velocity with an averaging time window equal to the integral time scale (T=T(int)) was 43% higher than the energy dissipation rate estimated from a constant advective velocity. The estimated dissipation rates with T=T(int) were comparable to values obtained by curve-fitting a theoretical Batchelor spectrum for the temperature gradient spectra. This study proposes the integral time scale to be used for the oscillatory flows as (a) a time-averaging window to estimate the advective velocity and associated energy dissipation level, and (b) a normalizing parameter in the energy spectrum.

  1. Fog-Influenced Submicron Aerosol Number Size Distributions

    NASA Astrophysics Data System (ADS)

    Zikova, N.; Zdimal, V.

    2013-12-01

    The aim of this work is to evaluate the influence of fog on aerosol particle number size distributions (PNSD) in submicron range. Thus, five-year continuous time series of the SMPS (Scanning Mobility Particle Sizer) data giving information on PNSD in five minute time step were compared with detailed meteorological records from the professional meteorological station Kosetice in the Czech Republic. The comparison included total number concentration and PNSD in size ranges between 10 and 800 nm. The meteorological records consist from the exact times of starts and ends of individual meteorological phenomena (with one minute precision). The records longer than 90 minutes were considered, and corresponding SMPS spectra were evaluated. Evaluation of total number distributions showed considerably lower concentration during fog periods compared to the period when no meteorological phenomenon was recorded. It was even lower than average concentration during presence of hydrometeors (not only fog, but rain, drizzle, snow etc. as well). Typical PNSD computed from all the data recorded in the five years is in Figure 1. Not only median and 1st and 3rd quartiles are depicted, but also 5th and 95th percentiles are plotted, to see the variability of the concentrations in individual size bins. The most prevailing feature is the accumulation mode, which seems to be least influenced by the fog presence. On the contrary, the smallest aerosol particles (diameter under 40 nm) are effectively removed, as well as the largest particles (diameter over 500 nm). Acknowledgements: This work was supported by the projects GAUK 62213 and SVV-2013-267308. Figure 1. 5th, 25th, 50th, 75th and 95th percentile of aerosol particle number size distributions recorded during fog events.

  2. Effusion of hydrophobic organic compounds (HOCs) from fog droplets

    SciTech Connect

    Lee, W.M.; Tsay, C.

    1998-12-31

    In this study, the effects of surface-active substances, pH and salt on the effusion of HOCs from droplets were investigated. An HOCs-effusion reactor was established for experiments. N-octane was used for the HOCs and Sodium Dodecyl Sulfate (SDS) was selected as the surface-active substance. A correction factor to mass exchange constant, defined as the deviation of exchange constant of n-octane in fog phase from that in planar aqueous phase was used to quantify the effects of surface-active substance, pH, and salt concentration on the effusion rate of HOCs from fog droplets by a modified double-layer diffusion model. The results showed that surface-active substances, SDS cab decrease the effusion rate of n-octane from fog droplets by about 40%--62% and the values of were in the range of 0.382 to 0.609. The salt, sodium chloride, at the concentration of 1.00 {times} 10{sup {minus}3} [M] can further decrease the mass transfer rate of n-octane from fog droplets because the values changed from 0.590 to 0.368, so that the effusion rate was further decrease by salt. When pH values were between 5.60 and 2.00, values varied from 0.609 to 0.367 at SDS concentration of 1.00 x 10{sup 3}[M]. This indicated that the effusion rate of HOCs from fog droplets decreased with decreasing pH value.

  3. Fat, oil and grease deposits in sewers: characterisation of deposits and formation mechanisms.

    PubMed

    Williams, J B; Clarkson, C; Mant, C; Drinkwater, A; May, E

    2012-12-01

    Fat, oil and grease deposits (FOG) in sewers are a major problem and can cause sewer overflows, resulting in environmental damage and health risks. Often simplistically portrayed as cooling of fats, recent research has suggested that saponification may be involved in FOG formation. However there are still questions about the mechanisms effecting transformations in sewers and the role and source of metal cations involved in saponification. This study characterises FOG deposits from pumping stations, sewers and sewage works from different water hardness zones across the UK. The sites all had previous problems with FOG and most catchments contained catering and food preparation establishments. The FOG deposits were highly variable with moisture content ranging from 15 to 95% and oil content from 0 to 548 mg/g. Generally the pumping stations had lower moisture content and higher fat content, followed by the sewers then the sewage works. The water in contact with the FOG had high levels of oil (mean of about 800 mg/L) and this may indicate poor kitchen FOG management practices. FOG fatty acid profiles showed a transformation from unsaturated to saturated forms compared to typical cooking oils. This seems to relate to ageing in the sewer network or the mechanism of formation, as samples from pumping stations had higher proportions of C18:1 compared to C16. This may be due to microbial transformations by bacteria such as Clostridium sp. in a similar process to adipocere formation. There was an association between water hardness and increased Ca levels in FOG along with harder deposits and higher melting points. A link between FOG properties and water hardness has not been previously reported for field samples. This may also be due to microbial processes, such as biocalcification. By developing the understanding of these mechanisms it may be possible to more effectively control FOG deposits, especially when combined with promotion of behavioural change.

  4. The effects of sequential exposure to acidic fog and ozone on pulmonary function in exercising subjects

    SciTech Connect

    Aris, R.; Christian, D.; Sheppard, D.; Balmes, J.R. )

    1991-01-01

    In Southern California coastal regions, morning fog is often acidified by the presence of nitric acid (HNO{sub 3}). Peak exposure to ozone (O{sub 3}) usually occurs in the afternoon and evening, after the fog has dissipated. To determine whether fog containing HNO{sub 3} might enhance pulmonary responses to O{sub 3}, we studied a group of healthy, athletic subjects selected for lung function sensitivity to O{sub 3}. On 3 separate days, the subjects exercised for 2 h in atmospheres containing HNO{sub 3} fog (0.5 mg/ml), H{sub 2}O fog, or clean, filtered air. After a 1-h break, they exercised for an additional 3 h in an atmosphere containing 0.20 ppm O{sub 3}. Surprisingly, the mean O{sub 3}-induced decrements in FEV1 and FVC were smaller after exercise in each fog-containing atmosphere than they were after exercise in clean, filtered air. The mean (+/- SEM) O{sub 3}-induced decrements in FEV1 were 26.4 +/- 5.3% after air, 17.1 +/- 3.7% after H{sub 2}O fog, and 18.0 +/- 4.3% after HNO{sub 3} fog, and in FVC they were 19.9 +/- 4.7% after air, 13.6 +/- 2.8% after H{sub 2}O fog, and 13.6 +/- 4.2% after HNO{sub 3} fog.

  5. Relative humidity patterns and fog water precipitation in the Atacama Desert and biological implications

    NASA Astrophysics Data System (ADS)

    CáCeres, Luis; Gómez-Silva, Benito; Garró, Ximena; RodríGuez, Violeta; Monardes, Vinka; McKay, Christopher P.

    2007-12-01

    Fog is the most important source of water for native plants and biological soil crusts in the Atacama Desert. Since fog depends upon available moisture, an understanding of climatic patterns is essential to interpret its present-day occurrence and distribution. In this work, temperature and humidity of ambient air and collected fog water in selected sites were studied across a transect from the coast to inland of the Atacama Desert, by using automated outdoor sensors for temperature and relative humidity, and also fog collectors equipped with automated rain gauges to measure collected fog water flow rates. Field measurements were organized to determine fog and collected fog water patterns at three selected sites, namely, Coloso, Inacesa and Yungay in addition to the relative humidity and temperature variation with altitude at Coloso Mountain located within Coloso site. The results show a decreasing trend in the collected fog water flow rates from the coast toward inland locations. Daily thermal oscillations at each site are closely related to fog water collection. At Coloso Mountain, an adiabatic cooling-like effect of the wind ascending its slope was observed preferentially during nighttime. At daytime, occasional distortions observed in the temperature profiles are probably produced by a thermal driven-air convection process along the Coloso Mountain slope heated by solar radiation. The reduction in available water from fog from the coast to the inland site is consistent with the reduction in colonization rate for hypolithic cyanobacteria along this same transect.

  6. Physical characterization, magnetic measurements, REE geochemistry and biomonitoring of dust load accumulated during a protracted winter fog period and their implications.

    PubMed

    Chakarvorty, Munmun; Pati, Jayanta Kumar; Patil, Shiva Kumar; Shukla, Swati; Niyogi, Ambalika; Saraf, Arun Kumar

    2014-05-01

    The winter fog in India is a recurrent phenomenon for more than a decade now affecting the entire Himalayan and sub-Himalayan regions covering an area of nearly 500,000 km(2). Every winter (December-January), the air and surface transports in cities of northern India (Amritsar, New Delhi, Agra, Gwalior, Kanpur, Lucknow, and Allahabad) are severely disrupted with visibility reduced to <50 m at times. Since dust particles are known to act as nuclei for the fog formation, this study is aimed to carry out physicochemical characterization of the dust particulates accumulated during a protracted fog period from one of the severely fog affected cities of north India (Allahabad; 25°27'33.40″N-81°52'45.47″E). The dust-loaded tree leaves belonging to Ficus bengalensis and Ficus religiosa from 50 different locations between January 24 and 31, 2010 are sampled and characterized. The mass of dust, color, grain shape, size, phase constituents, and mineral magnetic parameters, such as magnetic susceptibility, SIRM, χ fd%, and S-ratio, show minor variation and the regional influence outweighs local anthropogenic contributions. The dust compositions show fractionated rare earth element pattern with a pronounced negative Eu anomaly similar to upper continental crust and further suggesting their derivation from sources located in parts of north and central India.

  7. Application of a Particle Method to the Advection-Diffusion-Reaction Equation

    NASA Astrophysics Data System (ADS)

    Paster, A.; Bolster, D.; Benson, D. A.

    2012-12-01

    A reaction between two chemical species can only happen if molecules collide and react. Thus, the mixing of a system can become a limiting factor in the onset of reaction. Solving for reaction rate in a well-mixed system is typically a straightforward task. However, when incomplete mixing kicks in, obtaining a solution becomes more challenging. Since reaction can only happen in regions where both reactants co-exist, the incomplete mixing may slow down the reaction rate, when compared to a well-mixed system. The effect of incomplete mixing upon reaction is a highly important aspect of various processes in natural and engineered systems, ranging from mineral precipitation in geological formations to groundwater remediation in aquifers. We study a relatively simple system with a bi-molecular irreversible kinetic reaction A+B → Ø where the underlying transport of reactants is governed by an advection-diffusion equation, and the initial concentrations are given in terms of an average and a perturbation. Such a system does not have an analytical solution to date, even for the zero advection case. We model the system by a Monte Carlo particle tracking method, where particles represent some reactant mass. In this method, diffusion is modeled by a random walk of the particles, and reaction is modeled by annihilation of particles. The probability of the annihilation is proportional to the reaction rate constant and the probability density associated with particle co-location. We study the numerical method in depth, characterizing typical numerical errors and time step restrictions. In particular, we show that the numerical method converges to the advection-diffusion-reaction equation at the limit Δt →0. We also rigorously derive the relationship between the initial number of particles in the system and the initial concentrations perturbations represented by that number. We then use the particle simulations of zero-advection system to demonstrate the well

  8. Methylmercury and other chemical constituents in Pacific coastal fog water from seven sites in Central/Northern California (FogNet) during the summer of 2014

    NASA Astrophysics Data System (ADS)

    Weiss-Penzias, P. S.; Heim, W. A.; Fernandez, D.; Coale, K. H.; Oliphant, A. J.; Dann, D.; Porter, M.; Hoskins, D.; Dodge, C.

    2014-12-01

    This project investigates the mercury content in summertime Pacific coastal fog in California and whether fog could be an important vector for ocean emissions of mercury to be deposited via fog drip to upland coastal ecosystems. Efforts began in early 2014 with the building of 7 active-strand fog collectors based on the Colorado State University Caltech CASCC design. The new UCSC CASCC includes doors sealing the collector which open under microcomputer control based on environmental sensing (relative humidity). Seven sites spanning from Trinidad in the north to Marina in the south have collected samples June-August 2014 under a project called FogNet. Fog conditions were favorable for collecting large water volumes (> 250 mL) at many sites. Fog samplers were cleaned with soap and deionized water daily and field blanks taken immediately following cleaning. Fog water samples were collected overnight, split into an aliquot for anion and DOC/DIC analysis and the remaining sample was acidified. Monomethyl mercury (MMHg) concentrations in samples and field blanks for 3 sites in FogNet are shown in the accompanying figure. The range of MMHg concentrations from 10 fog water samples > 100 mL in volume was 0.9-9.3 ng/L (4.5-46.4 pM). Elevated MMHg concentrations (> 5 ng/L, 25 pM) were observed at 2 sites: UC Santa Cruz and Bodega Bay. The field blanks produced MMHg concentrations of 0.08-0.4 ng/L (0.4-2.0 pM), which was on average < 10% of the sample concentration and suggests the artifact due to sampling was small. The observed MMHg concentrations in fog water observed is this study are 1-2 orders of magnitude greater than MMHg concentrations seen previously in rain water samples from the California coast suggesting an additional source of MMHg to fog. Shipboard measurements of dimethyl mercury (DMHg) in coastal California seawater during the time period of FogNet operations (summer 2014) reveal surface waters that were supersaturated in DMHg which represents a potential

  9. Role of horizontal density advection in seasonal deepening of the mixed layer in the subtropical Southeast Pacific

    NASA Astrophysics Data System (ADS)

    Liu, Qinyu; Lu, Yiqun

    2016-04-01

    The mechanisms behind the seasonal deepening of the mixed layer (ML) in the subtropical Southeast Pacific were investigated using the monthly Argo data from 2004 to 2012. The region with a deep ML (more than 175 m) was found in the region of (22°-30°S, 105°-90°W), reaching its maximum depth (~200 m) near (27°-28°S, 100°W) in September. The relative importance of horizontal density advection in determining the maximum ML location is discussed qualitatively. Downward Ekman pumping is key to determining the eastern boundary of the deep ML region. In addition, zonal density advection by the subtropical countercurrent (STCC) in the subtropical Southwest Pacific determines its western boundary, by carrying lighter water to strengthen the stratification and form a "shallow tongue" of ML depth to block the westward extension of the deep ML in the STCC region. The temperature advection by the STCC is the main source for large heat loss from the subtropical Southwest Pacific. Finally, the combined effect of net surface heat flux and meridional density advection by the subtropical gyre determines the northern and southern boundaries of the deep ML region: the ocean heat loss at the surface gradually increases from 22?S to 35?S, while the meridional density advection by the subtropical gyre strengthens the stratification south of the maximum ML depth and weakens the stratification to the north. The freshwater flux contribution to deepening the ML during austral winter is limited. The results are useful for understanding the role of ocean dynamics in the ML formation in the subtropical Southeast Pacific.

  10. Permeability generation and resetting of tracers during metamorphic fluid flow: implications for advection-dispersion models

    NASA Astrophysics Data System (ADS)

    Cartwright, Ian

    Advection-dispersion fluid flow models implicitly assume that the infiltrating fluid flows through an already fluid-saturated medium. However, whether rocks contain a fluid depends on their reaction history, and whether any initial fluid escapes. The behaviour of different rocks may be illustrated using hypothetical marble compositions. Marbles with diverse chemistries (e.g. calcite + dolomite + quartz) are relatively reactive, and will generally produce a fluid during heating. By contrast, marbles with more restricted chemistries (e.g. calcite + quartz or calcite-only) may not. If the rock is not fluid bearing when fluid infiltration commences, mineralogical reactions may produce a reaction-enhanced permeability in calcite + dolomite + quartz or calcite + quartz, but not in calcite-only marbles. The permeability production controls the pattern of mineralogical, isotopic, and geochemical resetting during fluid flow. Tracers retarded behind the mineralogical fronts will probably be reset as predicted by the advection-dispersion models; however, tracers that are expected to be reset ahead of the mineralogical fronts cannot progress beyond the permeability generating reaction. In the case of very unreactive lithologies (e.g. pure calcite marbles, cherts, and quartzites), the first reaction to affect the rocks may be a metasomatic one ahead of which there is little pervasive resetting of any tracer. Centimetre-scale layering may lead to the formation of self-perpetuating fluid channels in rocks that are not fluid saturated due to the juxtaposition of reactants. Such layered rocks may show patterns of mineralogical resetting that are not predicted by advection-dispersion models. Patterns of mineralogical and isotopic resetting in marbles from a number of terrains, for example: Chillagoe, Marulan South, Reynolds Range (Australia); Adirondack Mountains, Old Woman Mountains, Notch Peak (USA); and Stephen Cross Quarry (Canada) vary as predicted by these models.

  11. Phase Segregation of Passive Advective Particles in an Active Medium

    NASA Astrophysics Data System (ADS)

    Das, Amit; Polley, Anirban; Rao, Madan

    2016-02-01

    Localized contractile configurations or asters spontaneously appear and disappear as emergent structures in the collective stochastic dynamics of active polar actomyosin filaments. Passive particles which (un)bind to the active filaments get advected into the asters, forming transient clusters. We study the phase segregation of such passive advective scalars in a medium of dynamic asters, as a function of the aster density and the ratio of the rates of aster remodeling to particle diffusion. The dynamics of coarsening shows a violation of Porod behavior; the growing domains have diffuse interfaces and low interfacial tension. The phase-segregated steady state shows strong macroscopic fluctuations characterized by multiscaling and intermittency, signifying rapid reorganization of macroscopic structures. We expect these unique nonequilibrium features to manifest in the actin-dependent molecular clustering at the cell surface.

  12. Chaotic Advection in a Bounded 3-Dimensional Potential Flow

    NASA Astrophysics Data System (ADS)

    Metcalfe, Guy; Smith, Lachlan; Lester, Daniel

    2012-11-01

    3-dimensional potential, or Darcy flows, are central to understanding and designing laminar transport in porous media; however, chaotic advection in 3-dimensional, volume-preserving flows is still not well understood. We show results of advecting passive scalars in a transient 3-dimensional potential flow that consists of a steady dipole flow and periodic reorientation. Even for the most symmetric reorientation protocol, neither of the two invarients of the motion are conserved; however, one invarient is closely shadowed by a surface of revolution constructed from particle paths of the steady flow, creating in practice an adiabatic surface. A consequence is that chaotic regions cover 3-dimensional space, though tubular regular regions are still transport barriers. This appears to be a new mechanism generating 3-dimensional chaotic orbits. These results contast with the experimental and theoretical results for chaotic scalar transport in 2-dimensional Darcy flows. Wiggins, J. Fluid Mech. 654 (2010).

  13. Advective-diffusive contaminant migration in unsaturated sand and gravel

    SciTech Connect

    Rowe, R.K.; Badv, K.

    1996-12-01

    A method is presented for estimating the diffusion coefficients for chloride and sodium in unsaturated coarse sand and fine gravel based on parameters obtained from saturated diffusion tests conducted for similar material. The method is tested by comparing the observed and predicted diffusion profiles through unsaturated soil. The method is shown to work well for predicting the advective-diffusive migration of chloride and sodium through a two-layer soil system consisting of a compacted clayey silt underlain by an unsaturated fine gravel. Over the range of conditions examined, it is concluded that existing solute transport theory along with the proposed procedure for estimating the unsaturated diffusion coefficients can adequately predict chloride and sodium diffusion through both unsaturated coarse sand and fine gravel as well as predict advective-diffusive transport through a compacted clayey layer and underlying unsaturated fine gravel.

  14. Fog-basking behaviour and water collection efficiency in Namib Desert Darkling beetles

    PubMed Central

    2010-01-01

    Background In the Namib Desert fog represents an alternative water source. This is utilised by Darkling beetles (Tenebrionidae) that employ different strategies for obtaining the fog water. Some dig trenches in the sand, while others use their own bodies as fog collectors assuming a characteristic fog-basking stance. Two beetle species from the genus Onymacris have been observed to fog-bask on the ridges of the sand dunes. These beetles all have smooth elytra surfaces, while another species with elytra covered in bumps is reported to have specialised adaptations facilitating water capture by fog-basking. To resolve if these other beetles also fog-bask, and if an elytra covered in bumps is a more efficient fog water collector than a smooth one, we examined four Namib Desert beetles; the smooth Onymacris unguicularis and O. laeviceps and the bumpy Stenocara gracilipes and Physasterna cribripes. Here we describe the beetles' fog-basking behaviour, the details of their elytra structures, and determine how efficient their dorsal surface areas are at harvesting water from fog. Results The beetles differ greatly in size. The largest P. cribripes has a dorsal surface area that is 1.39, 1.56, and 2.52 times larger than O. unguicularis, O. laeviceps, and S. gracilipes, respectively. In accordance with earlier reports, we found that the second largest O. unguicularis is the only one of the four beetles that assumes the head standing fog-basking behaviour, and that fog is necessary to trigger this behaviour. No differences were seen in the absolute amounts of fog water collected on the dorsal surface areas of the different beetles. However, data corrected according to the sizes of the beetles revealed differences. The better fog water harvesters were S. gracilipes and O. unguicularis while the large P. cribripes was the poorest. Examination of the elytra microstructures showed clear structural differences, but the elytra of all beetles were found to be completely hydrophobic

  15. Spectral Theory of Advective Diffusion in the Ocean

    DTIC Science & Technology

    2013-09-19

    to study this enhancement of sea ice thermal conductivity and better understand temperature data collected during a 2007 Antarctic expedition. 15...conductivity and better understand temperature data collected during a 2007 Antarctic expedition. Activities and Findings: 1. Advection-enhanced...critically on the properties of this Hilbert space. More specifically, it is only on a special subset of this space that the random operator is Hermitian

  16. Lattice Boltzmann method for the fractional advection-diffusion equation.

    PubMed

    Zhou, J G; Haygarth, P M; Withers, P J A; Macleod, C J A; Falloon, P D; Beven, K J; Ockenden, M C; Forber, K J; Hollaway, M J; Evans, R; Collins, A L; Hiscock, K M; Wearing, C; Kahana, R; Villamizar Velez, M L

    2016-04-01

    Mass transport, such as movement of phosphorus in soils and solutes in rivers, is a natural phenomenon and its study plays an important role in science and engineering. It is found that there are numerous practical diffusion phenomena that do not obey the classical advection-diffusion equation (ADE). Such diffusion is called abnormal or superdiffusion, and it is well described using a fractional advection-diffusion equation (FADE). The FADE finds a wide range of applications in various areas with great potential for studying complex mass transport in real hydrological systems. However, solution to the FADE is difficult, and the existing numerical methods are complicated and inefficient. In this study, a fresh lattice Boltzmann method is developed for solving the fractional advection-diffusion equation (LabFADE). The FADE is transformed into an equation similar to an advection-diffusion equation and solved using the lattice Boltzmann method. The LabFADE has all the advantages of the conventional lattice Boltzmann method and avoids a complex solution procedure, unlike other existing numerical methods. The method has been validated through simulations of several benchmark tests: a point-source diffusion, a boundary-value problem of steady diffusion, and an initial-boundary-value problem of unsteady diffusion with the coexistence of source and sink terms. In addition, by including the effects of the skewness β, the fractional order α, and the single relaxation time τ, the accuracy and convergence of the method have been assessed. The numerical predictions are compared with the analytical solutions, and they indicate that the method is second-order accurate. The method presented will allow the FADE to be more widely applied to complex mass transport problems in science and engineering.

  17. The LEM exponential integrator for advection-diffusion-reaction equations

    NASA Astrophysics Data System (ADS)

    Caliari, Marco; Vianello, Marco; Bergamaschi, Luca

    2007-12-01

    We implement a second-order exponential integrator for semidiscretized advection-diffusion-reaction equations, obtained by coupling exponential-like Euler and Midpoint integrators, and computing the relevant matrix exponentials by polynomial interpolation at Leja points. Numerical tests on 2D models discretized in space by finite differences or finite elements, show that the Leja-Euler-Midpoint (LEM) exponential integrator can be up to 5 times faster than a classical second-order implicit solver.

  18. Lattice Boltzmann method for the fractional advection-diffusion equation

    NASA Astrophysics Data System (ADS)

    Zhou, J. G.; Haygarth, P. M.; Withers, P. J. A.; Macleod, C. J. A.; Falloon, P. D.; Beven, K. J.; Ockenden, M. C.; Forber, K. J.; Hollaway, M. J.; Evans, R.; Collins, A. L.; Hiscock, K. M.; Wearing, C.; Kahana, R.; Villamizar Velez, M. L.

    2016-04-01

    Mass transport, such as movement of phosphorus in soils and solutes in rivers, is a natural phenomenon and its study plays an important role in science and engineering. It is found that there are numerous practical diffusion phenomena that do not obey the classical advection-diffusion equation (ADE). Such diffusion is called abnormal or superdiffusion, and it is well described using a fractional advection-diffusion equation (FADE). The FADE finds a wide range of applications in various areas with great potential for studying complex mass transport in real hydrological systems. However, solution to the FADE is difficult, and the existing numerical methods are complicated and inefficient. In this study, a fresh lattice Boltzmann method is developed for solving the fractional advection-diffusion equation (LabFADE). The FADE is transformed into an equation similar to an advection-diffusion equation and solved using the lattice Boltzmann method. The LabFADE has all the advantages of the conventional lattice Boltzmann method and avoids a complex solution procedure, unlike other existing numerical methods. The method has been validated through simulations of several benchmark tests: a point-source diffusion, a boundary-value problem of steady diffusion, and an initial-boundary-value problem of unsteady diffusion with the coexistence of source and sink terms. In addition, by including the effects of the skewness β , the fractional order α , and the single relaxation time τ , the accuracy and convergence of the method have been assessed. The numerical predictions are compared with the analytical solutions, and they indicate that the method is second-order accurate. The method presented will allow the FADE to be more widely applied to complex mass transport problems in science and engineering.

  19. Stability of explicit advection schemes. The balance point location rule

    NASA Astrophysics Data System (ADS)

    Leonard, B. P.

    2002-02-01

    This paper introduces the balance point location rule, providing specific necessary and sufficient conditions for constructing unconditionally stable explicit advection schemes, in both semi-Lagrangian and flux-form Eulerian formulations. The rule determines how the spatial stencil is placed on the computational grid. It requires the balance point (the center of the stencil in index space) to be located in the same patch as the departure point for semi-Lagrangian schemes or the same cell as the sweep point for Eulerian schemes. Centering the stencil in this way guarantees stability, regardless of the size of the time step. In contrast, the original Courant-Friedrichs-Lewy (CFL) condition requiring the stencil merely to include the departure (sweep) point, although necessary, is not sufficient for guaranteeing stability. The CFL condition is of limited practical value, whereas the balance point location rule always gives precise and easily implemented prescriptions for constructing stable algorithms. The rule is also helpful in correcting a number of misconceptions that have arisen concerning explicit advection schemes. In particular, explicit Eulerian schemes are widely believed to be inefficient because of stability constraints on the time step, dictated by a narrow interpretation of the CFL condition requiring the Courant number to be less than or equal to one. However, such constraints apply only to a particular class of advection schemes resulting for centering the stencil on the arrival point, when in fact the sole function of the stencil is to estimate the departure (sweep) point value - the arrival point has no relevance in determining the placement of the stencil. Unconditionally stable explicit Eulerian advection schemes are efficient and accurate, comparable in operation count to semi-Lagrangian schemes of the same order, but because of their flux-based formulation, they have the added advantage of being inherently conservative. Copyright

  20. Numerical Analysis of Thermo Hydraulic Conditions in Car Fog Lamp

    NASA Astrophysics Data System (ADS)

    Ramšak, M.; Žunič, Z.; Škerget, L.; Jurejevčič, T.

    2009-08-01

    In the article a coupled heat transfer in the solid and fluid inside of a car fog lamp is presented using CFD software CFX [1]. All three basic principles of heat transfer are dealt with: conduction, convection and radiation. Two different approaches to radiation modeling are compared. Laminar and turbulent flow modeling are compared since computed Rayleight number indicates transitional flow regime. Results are in good agreement with the measurements.

  1. Fog, Rain and Aerosol Attenuation in the Atmosphere.

    DTIC Science & Technology

    1987-12-31

    Genon, 1987; Turton and Brown, 1987) have included increasingly complicated treatments of turbulent vertical exchange processes , cloud microphysics...AS AN OFFICIAL DEPARTMENT OF THE ARMY POSITION, POLICY, OR DECISION, UNLESS SO DESIGNATED BY OTHER DOCUMENTATION. ., ’S 5’ 7 -I. r-,~. - " ’ U ~ I...information gathered in a small field project in 1985, which was designed to address new topics related to the fog problem. Included in this data set

  2. Modeling Fog Oil Obscurant Smoke Penetration into Simulated Tortoise Burrows

    DTIC Science & Technology

    2006-11-01

    requested by a petition in January 2006 (Save Our Big Scrub, Inc. and Wild South 2006 ). At least 18 military bases are known to have gopher tortoises...Wilson et al . 1997). Among the training activities that occur in or near the gopher tortoise habitat is troop preparedness training and the field...dispersion characteristics, and safety (Eberhard et al . 1989). SGF-2 fog oil (FO) is the obscurant used most frequently for military training

  3. Laser Imaging Video Camera Sees Through Fire, Fog, Smoke

    NASA Technical Reports Server (NTRS)

    2015-01-01

    Under a series of SBIR contracts with Langley Research Center, inventor Richard Billmers refined a prototype for a laser imaging camera capable of seeing through fire, fog, smoke, and other obscurants. Now, Canton, Ohio-based Laser Imaging through Obscurants (LITO) Technologies Inc. is demonstrating the technology as a perimeter security system at Glenn Research Center and planning its future use in aviation, shipping, emergency response, and other fields.

  4. [Microphysics of atmospheric aerosols during winter haze/fog events in Nanjing].

    PubMed

    Yang, Jun; Niu, Zhong-qing; Shi, Chun-e; Liu, Duan-yang; Li, Zi-hua

    2010-07-01

    Intensive field observations of fog/haze events, including simultaneous measurements of aerosol particle and fog droplet size distributions, were conducted in Nanjing in November, 2007. Four weather conditions (fog, mist, wet haze and haze) were distinguished based on visibility and liquid water content firstly. Then, the microphysical characteristics of coarse and fine particles in each condition were investigated. The results showed the dominant sequence of the four weather conditions was haze<-->mist-->wet haze-->fog-->, wet haze-->mist<-->haze. The lasting time of pre-fog wet haze was longer than that of post-fog wet haze. The number, surface area and volume concentration of coarse particles with diameter larger than 2.0 micron in fog were much higher than those in the other three conditions, and the smallest concentrations were observed in haze. The size distributions of surface area and volume concentration exhibited multi-peak in fog droplets, while it showed single peak for coarse particles in haze, mist and wet haze. For the fine particles with diameter larger than 0.010 microm, the spectral shapes of surface area concentration are similar in fog (mist) and wet haze (haze) condition. The dominant size ranges of fine particle number concentration were in 0.04-0.13 microm and 0.02-0.14 microm for fog and wet haze, separately. The same dominant size ranges located in 0.02-0.06 microm for both mist and haze. During the transition processes from haze, mist and wet haze to fog, the concentration of smaller particles (less than 0.060-0.090 microm) reduced and vice versa for the corresponding larger particles. Temporal variation of aerosol number concentration correlated well with the root mean diameters negatively during the observation period. The number concentration of aerosol was the lowest and the mean diameter was the largest in fog periods.

  5. Fixation and chemical analysis of single fog and rain droplets

    NASA Astrophysics Data System (ADS)

    Kasahara, M.; Akashi, S.; Ma, C.-J.; Tohno, S.

    Last decade, the importance of global environmental problems has been recognized worldwide. Acid rain is one of the most important global environmental problems as well as the global warming. The grasp of physical and chemical properties of fog and rain droplets is essential to make clear the physical and chemical processes of acid rain and also their effects on forests, materials and ecosystems. We examined the physical and chemical properties of single fog and raindrops by applying fixation technique. The sampling method and treatment procedure to fix the liquid droplets as a solid particle were investigated. Small liquid particles like fog droplet could be easily fixed within few minutes by exposure to cyanoacrylate vapor. The large liquid particles like raindrops were also fixed successively, but some of them were not perfect. Freezing method was applied to fix the large raindrops. Frozen liquid particles existed stably by exposure to cyanoacrylate vapor after freezing. The particle size measurement and the elemental analysis of the fixed particle were performed in individual base using microscope, and SEX-EDX, particle-induced X-ray emission (PIXE) and micro-PIXE analyses, respectively. The concentration in raindrops was dependent upon the droplet size and the elapsed time from the beginning of rainfall.

  6. Dew, fog, drizzle and rain water in Baku (Azerbaijan)

    NASA Astrophysics Data System (ADS)

    Meunier, D.; Beysens, D.

    2016-09-01

    Dwindling supplies of fresh water and climate changes have drawn attention to the need to find alternative sources of water globally. This study examines the potential of the semi-arid region of Baku (Azerbaijan) to exploit in particular dew, but also fog, drizzle and rain water. The Absheron Peninsular suffers from scarceness of water and non-hazardous water sources. Measurements were taken in this region on a 30° inclined plane passive condenser over a year (1/4/2010-31/3/2011) to determine the contribution and validity of using these alternative sources of water. The results show a significant relative contribution from these sources during this period (rain: 84 mm; dew: 15 mm; fog: 6 mm; drizzle: 13 mm). The fact that rain was measured within 23 km from the main station leads to uncertainties in its relative contribution. However, at least for the year under study, there are fair indications that collecting dew, fog and drizzle in addition to rain can significantly increase the collected atmospheric water with value estimated on order 40% ± 20%.

  7. Out of the fog: Catalyzing integrative capacity in interdisciplinary research.

    PubMed

    Piso, Zachary; O'Rourke, Michael; Weathers, Kathleen C

    2016-04-01

    Social studies of interdisciplinary science investigate how scientific collaborations approach complex challenges that require multiple disciplinary perspectives. In order for collaborators to meet these complex challenges, interdisciplinary collaborations must develop and maintain integrative capacity, understood as the ability to anticipate and weigh tradeoffs in the employment of different disciplinary approaches. Here we provide an account of how one group of interdisciplinary fog scientists intentionally catalyzed integrative capacity. Through conversation, collaborators negotiated their commitments regarding the ontology of fog systems and the methodologies appropriate to studying fog systems, thereby enhancing capabilities which we take to constitute integrative capacity. On the ontological front, collaborators negotiated their commitments by setting boundaries to and within the system, layering different subsystems, focusing on key intersections of these subsystems, and agreeing on goals that would direct further investigation. On the methodological front, collaborators sequenced various methods, anchored methods at different scales, validated one method with another, standardized the outputs of related methods, and coordinated methods to fit a common model. By observing the process and form of collaborator conversations, this case study demonstrates that social studies of science can bring into critical focus how interdisciplinary collaborators work toward an integrated conceptualization of study systems.

  8. Gluten-induced cognitive impairment ("brain fog") in coeliac disease.

    PubMed

    Yelland, Gregory W

    2017-03-01

    Much is known about the serious neurological effects of gluten ingestion in coeliac disease patients, such as sporadic ataxia and peripheral neuropathy, although the causal links to gluten are still under debate. However, such disorders are observed in only a small percentage of coeliac patients. Much less is known about the transient cognitive impairments to memory, attention, executive function, and the speed of cognitive processing reported by the majority of patients with coeliac disease. These mild degradations of cognitive functions, referred to as "brain fog," are yet to be formally recognized as a medical or psychological condition. However, subtle tests of cognitive function are measurable in untreated patients with coeliac disease and improve over the first 12 months' therapy with a gluten-free diet. Such deficits also occur in patients with Crohn's disease, particularly in association with systemic inflammatory activity. Thus, cognitive impairments associated with brain fog are psychologically and neurologically real and improve with adherence to a gluten-free diet. There is not yet sufficient evidence to provide a definitive account of the mechanism by which gluten ingestion causes the impairments to cognitive function associated with brain fog, but current evidence suggests that it is more likely that the causal factor is not directly related to exposure to gluten.

  9. Dense fog on the highway: Visual range monitoring in cars?

    NASA Technical Reports Server (NTRS)

    Hahn, W.; Krichbaumer, W.; Streicher, J.; Werner, CH.

    1992-01-01

    This paper reports on the development of a new sensor. Laser range-finders are currently installed in cars and trucks to measure the distance to a proceeding car (LEICA). A modification of such a sensor to measure visibility was made. The problems that had to be solved were: (1) choice of wavelength with relation to the human eye for visibility measurements; (2) dependency of the wavelength on atmospheric turbidity; (3) laser eye-safety; and (4) influence of multiple scattering at visibilities smaller than 200 m. The wavelength used for lidar sensors in the near infrared presents no real problems because the object to be sensed is fog appearing white which means that scattering from fog is wavelength independent. There are however differences in backscatter-to-extinction ratio for different fog and weather situations. The two solutions to these problems are polarization and multiple scattering. As known from airport operations of a laser ceilometer, one can use this multiple scattering contribution to determine the visibility.

  10. Web Interface for Modeling Fog Oil Dispersion During Training

    NASA Astrophysics Data System (ADS)

    Lozar, Robert C.

    2002-08-01

    Predicting the dispersion of military camouflage training materials-Smokes and Obscurants (SO)-is a rapidly improving science. The Defense Threat Reduction Agency (DTRA) developed the Hazard Prediction and Assessment Capability (HPAC), a software package that allows the modeling of the dispersion of several potentially detrimental materials. ERDC/CERL characterized the most commonly used SO material, fog oil in HPAC terminology, to predict the SO dispersion characteristics in various training scenarios that might have an effect on Threatened and Endangered Species (TES) at DoD installations. To make the configuration more user friendly, the researchers implemented an initial web-interface version of HPAC with a modifiable fog-oil component that can be applied at any installation in the world. By this method, an installation SO trainer can plan the location and time of fog oil training activities and is able to predict the degree to which various areas will be effected, particularly important in ensuring the appropriate management of TES on a DoD installation.

  11. Investigating the Seasonal and Diurnal Evolution of Fog and its Effect on the Hydrometeorological Regime in the Southern Appalachian Mountains Using a Mobile Observing Platform

    NASA Astrophysics Data System (ADS)

    Wilson, A. M.; Barros, A.

    2015-12-01

    Accurate, high resolution observations of fog and low clouds in regions of complex terrain are largely unavailable, due to a lack of existing in situ observations and obstacles to satellite observations such as ground clutter. For the past year, a mobile observing platform including a ground-based passive cavity aerosol spectrometer probe (PCASP-X2), an optical disdrometer (PARSIVEL-2), a tipping bucket rain gauge, and a Vaisala weather station, collocated with a Micro Rain Radar, has been recording observations in valley locations in the inner mountain region of the Southern Appalachian Mountains (SAM). In 2014, the SAM hosted a Global Precipitation Mission field campaign (the Integrated Precipitation and Hydrology Experiment), and during this experiment the platform was also collocated at various times with a microwave radiometer, W- and X- band radars, a Pluvio weighing rain gauge, a 2D video disdrometer, among other instruments. These observations will be discussed in the context of previous findings based on observations and model results (stochastic column model and the Advanced Research Weather and Forecasting Model (WRF)). Specifically, in previous work, seeder-feeder processes have been found to govern the enhancement of light rainfall in the SAM through increased coalescence efficiency in stratiform rainfall due to the interactions with low level clouds and topography modulated fog. This presentation will focus on measurements made by the platform and collocated instruments, as well as observations made by fog collectors on ridges, with the aim of developing a process-based understanding of the characteristics of low cloud and fog through describing the diurnal cycle of microphysical and dynamical processes and properties in the region. The overarching goal is to employ observations of the formation and evolution of the "feeder" clouds and fog to further understand the magnitude and function of their contribution to the local hydrometeorological regime.

  12. Advective and Conductive Heat Flow Budget Across the Wagner Basin, Northern Gulf of California

    NASA Astrophysics Data System (ADS)

    Neumann, F.; Negrete-Aranda, R.; Contreras, J.; Müller, C.; Hutnak, M.; Gonzalez-Fernandez, A.; Harris, R. N.; Sclater, J. G.

    2015-12-01

    In May 2015, we conducted a cruise across the northern Gulf of California, an area of continental rift basin formation and rapid deposition of sediments. The cruise was undertaken aboard the R/V Alpha Helix; our goal was to study variation in superficial conductive heat flow, lateral changes in the shallow thermal conductivity structure, and advective transport of heat across the Wagner basin. We used a Fielax heat flow probe with 22 thermistors that can penetrate up to 6 m into the sediment cover. The resulting data set includes 53 new heat flow measurements collected along three profiles. The longest profile (42 km) contains 30 measurements spaced 1-2 km apart. The western part of the Wagner basin (hanging wall block) exhibit low to normal conductive heat flow whereas the eastern part of the basin (foot wall block) heat flow is high to very high (up to 2500 mWm-2). Two other short profiles (12 km long each) focused on resolving an extremely high heat flow anomaly up to 15 Wm-2 located near the intersection between the Wagner bounding fault system and the Cerro Prieto fault. We hypothesize that the contrasting heat flow values observed across the Wagner basin are due to horizontal water circulation through sand layers and fault pathways of high permeability. Circulation appears to be from west (recharge zone) to east (discharge zone). Additionally, our results reveal strong vertical advection of heat due to dehydration reactions and compaction of fine grained sediments.

  13. Striped pattern selection by advective reaction-diffusion systems: Resilience of banded vegetation on slopes

    NASA Astrophysics Data System (ADS)

    Siero, E.; Doelman, A.; Eppinga, M. B.; Rademacher, J. D. M.; Rietkerk, M.; Siteur, K.

    2015-03-01

    For water-limited arid ecosystems, where water distribution and infiltration play a vital role, various models have been set up to explain vegetation patterning. On sloped terrains, vegetation aligned in bands has been observed ubiquitously. In this paper, we consider the appearance, stability, and bifurcations of 2D striped or banded patterns in an arid ecosystem model. We numerically show that the resilience of the vegetation bands is larger on steeper slopes by computing the stability regions (Busse balloons) of striped patterns with respect to 1D and transverse 2D perturbations. This is corroborated by numerical simulations with a slowly decreasing water input parameter. Here, long wavelength striped patterns are unstable against transverse perturbations, which we also rigorously prove on flat ground through an Evans function approach. In addition, we prove a "Squire theorem" for a class of two-component reaction-advection-diffusion systems that includes our model, showing that the onset of pattern formation in 2D is due to 1D instabilities in the direction of advection, which naturally leads to striped patterns.

  14. Numerical simulation of diurnally varying thermal environment in a street canyon under haze-fog conditions

    NASA Astrophysics Data System (ADS)

    Tan, Zijing; Dong, Jingliang; Xiao, Yimin; Tu, Jiyuan

    2015-10-01

    The impact of haze-fog on surface temperature, flow pattern, pollutant dispersion and pedestrian thermal comfort are investigated using computational fluid dynamics (CFD) approach based on a three-dimensional street canyon model under different haze-fog conditions. In this study, light extinction coefficient (Kex) is adopted to represent haze-fog pollution level. Numerical simulations are performed for different Kex values at four representative time events (1000 LST, 1300 LST, 1600 LST and 2000 LST). The numerical results suggest that the surface temperature is strongly affected by the haze-fog condition. Surface heating induced by the solar radiation is enhanced by haze-fog, as higher surface temperature is observed under thicker haze-fog condition. Moreover, the temperature difference between sunlit and shadow surfaces is reduced, while that for the two shadow surfaces is slightly increased. Therefore, the surface temperature among street canyon facets becomes more evenly distributed under heavy haze-fog conditions. In addition, flow patterns are considerably altered by different haze-fog conditions, especially for the afternoon (1600 LST) case, in which thermal-driven flow has opposite direction as that of the wind-driven flow direction. Consequently, pollutants such as vehicular emissions will accumulate at pedestrian level, and pedestrian thermal comfort may lower under thicker haze-fog condition.

  15. Preliminary Research on Radiance Fog Detection based on time series MTSAT data

    NASA Astrophysics Data System (ADS)

    Wen, X.; Li, Z.; Zhang, S.; Shen, S.; Hu, D.; Xiao, X.

    2015-04-01

    Fog is a kind of disastrous weather phenomenon. In this paper, the geostationary satellite MTSAT imagery is selected as the main data source to radiance fog detection. According to the unique feature of radiance fog from its generation to dissipation, especially considering the difference between clouds and fog during their lifecycle, the characteristics in frequency domain was constructed to discriminate fog from clouds, The time series MTSAT images were register with a modified Gauss Newton optimization method firstly, then, the Savitzky-Golay smoothing filter was applied to the time series remote sensing imageries to process the noises in the original signal, after that the non-orthogonal Haar wavelets was applied to convert the signal from time domain into frequency domain. The coefficient of high frequency component, including the properties: "max", "min", "the location of the min", "the interval length between the max and min", "the coefficient of linear fit for the high frequency", these properties are selected as the characteristic parameters to distinguish fog from clouds. The experiment shows that using the algorithm proposed in this paper, the radiance fog could be monitored effectively, and it is found that although it is difficult to calculate the thickness of the fog directly, while the duration of fog could be obtained by using the frequency feature.

  16. Daytime sea fog retrieval based on GOCI data: a case study over the Yellow Sea.

    PubMed

    Yuan, Yibo; Qiu, Zhongfeng; Sun, Deyong; Wang, Shengqiang; Yue, Xiaoyuan

    2016-01-25

    In this paper, a new daytime sea fog detection algorithm has been developed by using Geostationary Ocean Color Imager (GOCI) data. Based on spectral analysis, differences in spectral characteristics were found over different underlying surfaces, which include land, sea, middle/high level clouds, stratus clouds and sea fog. Statistical analysis showed that the Rrc (412 nm) (Rayleigh Corrected Reflectance) of sea fog pixels is approximately 0.1-0.6. Similarly, various band combinations could be used to separate different surfaces. Therefore, three indices (SLDI, MCDI and BSI) were set to discern land/sea, middle/high level clouds and fog/stratus clouds, respectively, from which it was generally easy to extract fog pixels. The remote sensing algorithm was verified using coastal sounding data, which demonstrated that the algorithm had the ability to detect sea fog. The algorithm was then used to monitor an 8-hour sea fog event and the results were consistent with observational data from buoys data deployed near the Sheyang coast (121°E, 34°N). The goal of this study was to establish a daytime sea fog detection algorithm based on GOCI data, which shows promise for detecting fog separately from stratus.

  17. 1995 Integrated Monitoring Study: Fog measurements in the Northern San Joaquin Valley - preliminary results

    SciTech Connect

    Collett, J. Jr.; Bator, A.; Sherman, D.E.

    1996-12-31

    Vertical gradients in fog chemistry and physics were measured from a 430 m television broadcast tower in the northern San Joaquin Valley near Walnut Grove, California. Fog was collected on the ground and at two elevations on the tower using Caltech Active Strand Cloudwater Collectors Version 2 (CASCC2). Work was conducted as part of the 1995 Integrated Monitoring Study (IMS95). Results will be used to evaluate the need to make measurements aloft in future regional studies of fog processing of atmospheric particles and for testing whether vertically resolved fog models provide realistic simulations of fog physics and chemistry above the ground. Two fog/low cloud events were sampled during the tower study. Preliminary results show concentrations of major species in the fogwater typically decreasing with altitude, while liquid water contents increase. Fogwater loadings of major species, the total amount of a species in the aqueous phase per unit air volume, were observed to increase with altitude. Major species concentrations were typically quite stable at a given elevation, while significant decreases were observed over time in liquid water content. Fogwater concentrations of soluble hydroperoxides were highest near the surface and increased with time after sunrise and were observed to coexist in the high pH fog with S(IV). Time lapse video footage of the top of the fog/cloud layer revealed a very dynamic interface, suggesting entrainment of material from the clear air into the fog/cloud may be significant. 12 refs., 7 figs.

  18. Processing of atmospheric polycyclic aromatic hydrocarbons by fog in an urban environment.

    PubMed

    Ehrenhauser, Franz S; Khadapkar, Kalindi; Wang, Youliang; Hutchings, James W; Delhomme, Olivier; Kommalapati, Raghava R; Herckes, Pierre; Wornat, Mary J; Valsaraj, Kalliat T

    2012-10-26

    Polycyclic aromatic hydrocarbons (PAH) are ubiquitous pollutants in the atmosphere, predominantly known for their toxicity. Although there has been substantial work on the atmospheric degradation of PAH, little is known about how the presence of atmospheric droplets (e.g., a fog cloud) affects the fate of PAH. In order to assess the processing of PAH and their corresponding oxidation products during a fog event, two field-sampling campaigns in Fresno, CA and Davis, CA were conducted. The simultaneous evaluation of concentrations of the PAH and oxygenated polycyclic aromatic compounds (OPAC) in the gas phase, particulate matter and fog water droplets before, during and after fog allows for the characterization of transformative and transport processes in a fog cloud. By tracking the ratio of OPAC to PAH in the individual atmospheric phases, two major polycyclic aromatic compounds-processing pathways can be identified: (i) the dissolution of OPAC from particulate matter and (ii) the uptake and oxidation of PAH in the fog water droplets. Wet deposition steadily decreases the pollutant concentration in the fog cloud droplets during a fog event; however, uptake and concentration via evaporative water loss upon the dissipation of a fog cloud cause an increase in the atmospheric pollutant concentration.

  19. Investigating factors leading to fogging of glass vials in lyophilized drug products.

    PubMed

    Abdul-Fattah, Ahmad M; Oeschger, Richard; Roehl, Holger; Bauer Dauphin, Isabelle; Worgull, Martin; Kallmeyer, Georg; Mahler, Hanns-Christian

    2013-10-01

    Vial "Fogging" is a phenomenon observed after lyophilization due to drug product creeping upwards along the inner vial surface. After the freeze-drying process, a haze of dried powder is visible inside the drug product vial, making it barely acceptable for commercial distribution from a cosmetic point of view. Development studies were performed to identify the root cause for fogging during manufacturing of a lyophilized monoclonal antibody drug product. The results of the studies indicate that drug product creeping occurs during the filling process, leading to vial fogging after lyophilization. Glass quality/inner surface, glass conversion/vial processing (vial "history") and formulation excipients, e.g., surfactants (three different surfactants were tested), all affect glass fogging to a certain degree. Results showed that the main factor to control fogging is primarily the inner vial surface hydrophilicity/hydrophobicity. While Duran vials were not capable of reliably improving the level of fogging, hydrophobic containers provided reliable means to improve the cosmetic appearance due to reduction in fogging. Varying vial depyrogenation treatment conditions did not lead to satisfying results in removal of the fogging effect. Processing conditions of the vial after filling with drug product had a strong impact on reducing but not eliminating fogging.

  20. Canopy-atmosphere interactions under foggy condition—Size-resolved fog droplet fluxes and their implications

    NASA Astrophysics Data System (ADS)

    El-Madany, T. S.; Walk, J. B.; Deventer, M. J.; Degefie, D. T.; Chang, S.-C.; Juang, J.-Y.; Griessbaum, F.; Klemm, O.

    2016-03-01

    Microphysical processes of fog and their spatial and temporal pattern are a challenge to study under natural conditions. This work focuses on the development of bidirectional fluxes of fog droplets above a forest canopy in northeastern Taiwan. Bidirectional fluxes occurred regularly, start from the smallest droplet class (<2.66 µm diameter), and subsequently extend to larger droplets up to 7.41 µm diameter. The development of the bidirectional fluxes with positive (upward) fluxes of smaller droplets and downward fluxes of larger fluxes is associated with a temperature gradient and with the activation of fog droplets according to the Köhler theory. Small fog droplets develop close to the canopy as result of evapotranspiration and subsequent condensation. The rapid growth of small fog droplets and the accelerated growth of activated droplets, a process which is more likely to occur at higher levels of the fog layer, lead to a sink of small droplets and a source of larger droplets within the fog. This is in accordance with the observation that positive droplet number fluxes of small fog droplets outnumber the negative fluxes from the larger fog droplets. For liquid water, the net flux is negative.

  1. Pathogen and chemical transport in the karst limestone of the Biscayne aquifer: 2. Chemical retention from diffusion and slow advection

    USGS Publications Warehouse

    Shapiro, A.M.; Renken, R.A.; Harvey, R.W.; Zygnerski, M.R.; Metge, D.W.

    2008-01-01

    A tracer experiment, using a nonreactive tracer, was conducted as part of an investigation of the potential for chemical and pathogen migration to public supply wells that draw groundwater from the highly transmissive karst limestone of the Biscayne aquifer in southeastern Florida. The tracer was injected into the formation over approximately 1 h, and its recovery was monitored at a pumping well approximately 100 m from the injection well. The first detection of the tracer occurred after approximately 5 h, and the peak concentration occurred at about 8 h after the injection. The tracer was still detected in the production well more than 6 days after injection, and only 42% of the tracer mass was recovered. It is hypothesized that a combination of chemical diffusion and slow advection resulted in significant retention of the tracer in the formation, despite the high transmissivity of the karst limestone. The tail of the breakthrough curve exhibited a straight-line behavior with a slope of -2 on a log-log plot of concentration versus time. The -2 slope is hypothesized to be a function of slow advection, where the velocities of flow paths are hypothesized to range over several orders of magnitude. The flow paths having the slowest velocities result in a response similar to chemical diffusion. Chemical diffusion, due to chemical gradients, is still ongoing during the declining limb of the breakthrough curve, but this process is dwarfed by the magnitude of the mass flux by slow advection.

  2. Investigations of Scalar Transfer Coefficients in Fog During the Coupled Boundary Layers and Air-Sea Transfer Experiment: A Case Study

    DTIC Science & Technology

    2004-09-01

    mentioned, the disadvantage is that the important processes in fog formation take place below one meter (Wang 2004; Binhua 1985; Turton and Brown...formula under these conditions by examining the physical processes that are unique to these boundary layers. Particular attention will be paid to the...to moderate wind conditions. The experiment was designed to measure fluxes and their associated profiles so that every term within the turbulent

  3. Experimental FSO network availability estimation using interactive fog condition monitoring

    NASA Astrophysics Data System (ADS)

    Turán, Ján.; Ovseník, Łuboš

    2016-12-01

    Free Space Optics (FSO) is a license free Line of Sight (LOS) telecommunication technology which offers full duplex connectivity. FSO uses infrared beams of light to provide optical broadband connection and it can be installed literally in a few hours. Data rates go through from several hundreds of Mb/s to several Gb/s and range is from several 100 m up to several km. FSO link advantages: Easy connection establishment, License free communication, No excavation are needed, Highly secure and safe, Allows through window connectivity and single customer service and Compliments fiber by accelerating the first and last mile. FSO link disadvantages: Transmission media is air, Weather and climate dependence, Attenuation due to rain, snow and fog, Scattering of laser beam, Absorption of laser beam, Building motion and Air pollution. In this paper FSO availability evaluation is based on long term measured data from Fog sensor developed and installed at TUKE experimental FSO network in TUKE campus, Košice, Slovakia. Our FSO experimental network has three links with different physical distances between each FSO heads. Weather conditions have a tremendous impact on FSO operation in terms of FSO availability. FSO link availability is the percentage of time over a year that the FSO link will be operational. It is necessary to evaluate the climate and weather at the actual geographical location where FSO link is going to be mounted. It is important to determine the impact of a light scattering, absorption, turbulence and receiving optical power at the particular FSO link. Visibility has one of the most critical influences on the quality of an FSO optical transmission channel. FSO link availability is usually estimated using visibility information collected from nearby airport weather stations. Raw data from fog sensor (Fog Density, Relative Humidity, Temperature measured at each ms) are collected and processed by FSO Simulator software package developed at our Department. Based

  4. A method for simple and accurate estimation of fog deposition in a mountain forest using a meteorological model

    NASA Astrophysics Data System (ADS)

    Katata, Genki; Kajino, Mizuo; Hiraki, Takatoshi; Aikawa, Masahide; Kobayashi, Tomiki; Nagai, Haruyasu

    2011-10-01

    To apply a meteorological model to investigate fog occurrence, acidification and deposition in mountain forests, the meteorological model WRF was modified to calculate fog deposition accurately by the simple linear function of fog deposition onto vegetation derived from numerical experiments using the detailed multilayer atmosphere-vegetation-soil model (SOLVEG). The modified version of WRF that includes fog deposition (fog-WRF) was tested in a mountain forest on Mt. Rokko in Japan. fog-WRF provided a distinctly better prediction of liquid water content of fog (LWC) than the original version of WRF. It also successfully simulated throughfall observations due to fog deposition inside the forest during the summer season that excluded the effect of forest edges. Using the linear relationship between fog deposition and altitude given by the fog-WRF calculations and the data from throughfall observations at a given altitude, the vertical distribution of fog deposition can be roughly estimated in mountain forests. A meteorological model that includes fog deposition will be useful in mapping fog deposition in mountain cloud forests.

  5. Fog-2, a Germ-Line-Specific Sex Determination Gene Required for Hermaphrodite Spermatogenesis in Caenorhabditis Elegans

    PubMed Central

    Schedl, T.; Kimble, J.

    1988-01-01

    This paper describes the isolation and characterization of 16 mutations in the germ-line sex determination gene fog-2 (fog for feminization of the germ line). In the nematode Caenorhabditis elegans there are normally two sexes, self-fertilizing hermaphrodites (XX) and males (XO). Wild-type XX animals are hermaphrodite in the germ line (spermatogenesis followed by oogenesis), and female in the soma. fog-2 loss-of-function mutations transform XX animals into females while XO animals are unaffected. Thus, wild-type fog-2 is necessary for spermatogenesis in hermaphrodites but not males. The fem genes and fog-1 are each essential for specification of spermatogenesis in both XX and XO animals. fog-2 acts as a positive regulator of the fem genes and fog-1. The tra-2 and tra-3 genes act as negative regulators of the fem genes and fog-1 to allow oogenesis. Two models are discussed for how fog-2 might positively regulate the fem genes and fog-1 to permit spermatogenesis; fog-2 may act as a negative regulator of tra-2 and tra-3, or fog-2 may act positively on the fem genes and fog-1 rendering them insensitive to the negative action of tra-2 and tra-3. PMID:3396865

  6. Can fog contribute to the nutrition of Chamaecyparis obtusa var. formosana? Uptake of a fog solute tracer into foliage and transport to roots.

    PubMed

    Lai, I-Ling; Schroeder, Walter H; Wu, Jiunn-Tzong; Kuo-Huang, Ling-Long; Mohl, Carola; Chou, Chang-Hung

    2007-07-01

    Yellow cypress (Chamaecyparis obtusa (Siebold & Zucc.) Endl. var. formosana (Hayata) Rehder) is the predominant tree species of Taiwan's nutrient-poor, mountain fog forests. Little is known about the potential contribution of solute uptake from fog to the overall nutrition of these trees. Shoots of yellow cypress seedlings were misted with artificial fog containing the tracer rubidium (Rb) in laboratory and field experiments to determine if there is solute uptake from the fog. After misting shoots for six weeks, substantial amounts of tracer were detected in unexposed roots by inductively coupled plasma mass spectroscopy bulk analysis. Possible routes of entry were examined by element imaging with energy dispersive X-ray analysis. Direct uptake of the tracer into leaves across the cuticle and epidermis was small, excluding this as the major uptake path. Accumulations of Rb were found on leaf surfaces along the edges of the leaves. The almost daily changes in fog coverage and air humidity may enhance the accumulation of fog solutes at leaf edges. Accumulation of Rb was also found in narrow clefts between opposite leaves and between the outermost and underlying alternating stacked leaves. The clefts provide a direct passage from the leaf surface to the space beneath the imbricate leaves and the underlying alternate leaves, possibly facilitating solute uptake from fog, which in turn may contribute to the nutrition of yellow cypress.

  7. Processing of Ambient Aerosols During Fog Events: Role of Acidity

    NASA Astrophysics Data System (ADS)

    Chakraborty, A.; Gupta, T.; Tripathi, S. N.; Bhattu, D.

    2013-12-01

    Fog is a major processing and removal agent of ambient aerosols. Enhanced secondary organic aerosol (SOA) production has been reported during fog events indicating major role of aqueous processing. Present study was carried out in a heavily polluted city of Kanpur situated in Indo-Gangetic plain of India,from 02- 18 Nov, 2012 and then from 22 Dec, 2012 to 10 January, 2013. 12 fog events were identified from 22 Dec to 10 January based on low visibility (< 300 m) with high liquid water content (~ 0.04 g/m3) and termed as foggy period while remaining as non-foggy period. Foggy period typically showed very high RH (~95%), low temperatures (~2-6°C) compared to non-foggy period. An array of instruments were deployed during this campaign for real time measurement of aerosol physico-chemical properties - High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS), Scanning Mobility Particle Sizer (SMPS), Cloud Combination Probe (CCP), Cloud Condensation Nuclei counter (CCN), fog water collector and Vaisala RH & T sensor. Average aerosol loading during foggy period was 104×44 μg/m3, much higher than 73×49 μg/m3of non-foggy period, but during actual fog events the loading reduced to 85×23 μg/m3 indicating overall aerosol removal by fog. Overall aerosol composition during both the period was dominated by organics which constitutes about 60-70% of the total AMS mass followed by nitrate, but during foggy period sulfate was found to be increased many fold.HR analysis of AMS data revealed noticeable differences in the diurnal average values of O:C ratio between foggy and non -foggy period. Although diurnal O:C ratio was highest around noontime for both period but during fog events, night to early morning O:C ratio was 0.51×0.04, higher than that of non-foggy period 0.44×0.07, clearly indicating enhanced oxidation. AMS data also showed that mode size of all the species specially of organics and sulphate had shifted to a higher diameter during foggy period, an

  8. Analyzing critical propagation in a reaction-diffusion-advection model using unstable slow waves.

    PubMed

    Kneer, Frederike; Obermayer, Klaus; Dahlem, Markus A

    2015-02-01

    The effect of advection on the propagation and in particular on the critical minimal speed of traveling waves in a reaction-diffusion model is studied. Previous theoretical studies estimated this effect on the velocity of stable fast waves and predicted the existence of a critical advection strength below which propagating waves are not supported anymore. In this paper, an analytical expression for the advection-velocity relation of the unstable slow wave is derived. In addition, the critical advection strength is calculated taking into account the unstable slow wave solution. We also analyze a two-variable reaction-diffusion-advection model numerically in a wide parameter range. Due to the new control parameter (advection) we can find stable wave propagation in the otherwise non-excitable parameter regime, if the advection strength exceeds a critical value. Comparing theoretical predictions to numerical results, we find that they are in good agreement. Theory provides an explanation for the observed behaviour.

  9. Cloud and fog interactions with coastal forests in the California Channel Islands

    NASA Astrophysics Data System (ADS)

    Still, C. J.; Baguskas, S. A.; Williams, P.; Fischer, D. T.; Carbone, M. S.; Rastogi, B.

    2015-12-01

    Coastal forests in California are frequently covered by clouds or immersed in fog in the rain-free summer. Scientists have long surmised that fog might provide critical water inputs to these forests. However, until recently, there has been little ecophysiological research to support how or why plants should prefer foggy regions; similarly, there is very little work quantifying water delivered to ecosystems by fog drip except for a few notable sites along the California coast. However, without spatial datasets of summer cloudcover and fog inundation, combined with detailed process studies, questions regarding the roles of cloud shading and fog drip in dictating plant distributions and ecosystem physiology cannot be addressed effectively. The overall objective of this project is to better understand how cloudcover and fog influence forest metabolism, growth, and distribution. Across a range of sites in California's Channel Islands National Park we measured a wide variety of ecosystem processes and properties. We then related these to cloudcover and fog immersion maps created using satellite datasets and airport and radiosonde observations. We compiled a spatially continuous dataset of summertime cloudcover frequency of the Southern California bight using satellite imagery from the NOAA geostationary GOES-11 Imager. We also created map of summertime cloudcover frequency of this area using MODIS imagery. To assess the ability of our mapping approach to predict spatial and temporal fog inundation patterns, we compared our monthly average daytime fog maps for GOES pixels corresponding to stations where fog inputs were measured with fog collectors in a Bishop pine forest. We also compared our cloudcover maps to measurements of irradiance measurements. Our results demonstrate that cloudcover and fog strongly modulate radiation, water, and carbon budgets, as well as forest distributions, in this semi-arid environment. Measurements of summertime fog drip, pine sapflow and

  10. An automated fog monitoring system for the Indo-Gangetic Plains based on satellite measurements

    NASA Astrophysics Data System (ADS)

    Patil, Dinesh; Chourey, Reema; Rizvi, Sarwar; Singh, Manoj; Gautam, Ritesh

    2016-05-01

    Fog is a meteorological phenomenon that causes reduction in regional visibility and affects air quality, thus leading to various societal and economic implications, especially disrupting air and rail transportation. The persistent and widespread winter fog impacts the entire the Indo-Gangetic Plains (IGP), as frequently observed in satellite imagery. The IGP is a densely populated region in south Asia, inhabiting about 1/6th of the world's population, with a strong upward pollution trend. In this study, we have used multi-spectral radiances and aerosol/cloud retrievals from Terra/Aqua MODIS data for developing an automated web-based fog monitoring system over the IGP. Using our previous and existing methodologies, and ongoing algorithm development for the detection of fog and retrieval of associated microphysical properties (e.g. fog droplet effective radius), we characterize the widespread fog detection during both daytime and nighttime. Specifically, for the night time fog detection, the algorithm employs a satellite-based bi-spectral brightness temperature difference technique between two spectral channels: MODIS band-22 (3.9μm) and band-31 (10.75μm). Further, we are extending our algorithm development to geostationary satellites, for providing continuous monitoring of the spatial-temporal variation of fog. We anticipate that the ongoing and future development of a fog monitoring system would be of assistance to air, rail and vehicular transportation management, as well as for dissemination of fog information to government agencies and general public. The outputs of fog detection algorithm and related aerosol/cloud parameters are operationally disseminated via http://fogsouthasia.com/.

  11. Visualizing Vector Fields Using Line Integral Convolution and Dye Advection

    NASA Technical Reports Server (NTRS)

    Shen, Han-Wei; Johnson, Christopher R.; Ma, Kwan-Liu

    1996-01-01

    We present local and global techniques to visualize three-dimensional vector field data. Using the Line Integral Convolution (LIC) method to image the global vector field, our new algorithm allows the user to introduce colored 'dye' into the vector field to highlight local flow features. A fast algorithm is proposed that quickly recomputes the dyed LIC images. In addition, we introduce volume rendering methods that can map the LIC texture on any contour surface and/or translucent region defined by additional scalar quantities, and can follow the advection of colored dye throughout the volume.

  12. Update on Advection-Diffusion Purge Flow Model

    NASA Technical Reports Server (NTRS)

    Brieda, Lubos

    2015-01-01

    Gaseous purge is commonly used in sensitive spacecraft optical or electronic instruments to prevent infiltration of contaminants and/or water vapor. Typically, purge is sized using simplistic zero-dimensional models that do not take into account instrument geometry, surface effects, and the dependence of diffusive flux on the concentration gradient. For this reason, an axisymmetric computational fluid dynamics (CFD) simulation was recently developed to model contaminant infiltration and removal by purge. The solver uses a combined Navier-Stokes and Advection-Diffusion approach. In this talk, we report on updates in the model, namely inclusion of a particulate transport model.

  13. Subsurface barrier design alternatives for confinement and controlled advection flow

    SciTech Connect

    Phillips, S.J.; Stewart, W.E.; Alexander, R.G.; Cantrell, K.J.; McLaughlin, T.J.

    1994-02-01

    Various technologies and designs are being considered to serve as subsurface barriers to confine or control contaminant migration from underground waste storage or disposal structures containing radioactive and hazardous wastes. Alternatives including direct-coupled flood and controlled advection designs are described as preconceptual examples. Prototype geotechnical equipment for testing and demonstration of these alternative designs tested at the Hanford Geotechnical Development and Test Facility and the Hanford Small-Tube Lysimeter Facility include mobile high-pressure injectors and pumps, mobile transport and pumping units, vibratory and impact pile drivers, and mobile batching systems. Preliminary laboratory testing of barrier materials and additive sequestering agents have been completed and are described.

  14. Is Chaotic Advection Inherent to Porous Media Flow?

    NASA Astrophysics Data System (ADS)

    Lester, Daniel; Metcalfe, Guy; Trefry, Mike

    2013-11-01

    All porous media, including granular and packed media, fractured and open networks, are typified by the inherent topological complexity of the pore-space. This topological complexity admits a large number density of stagnation points under steady Stokes flow, which in turn generates a 3D fluid mechanical analouge of the Bakers map, termed the Baker's flow. We demonstrate that via this mechanism, chaotic advection at the pore-scale is inherent to almost all porous media under reasonable conditions, and such dynamics have significant implications for a range of fluid-borne processes including transport and mixing, chemical reactions and biological activity.

  15. Vortex emission accompanies the advection of optical localized structures.

    PubMed

    Haudin, F; Rojas, R G; Bortolozzo, U; Clerc, M G; Residori, S

    2011-02-11

    We show that the advection of optical localized structures is accompanied by the emission of vortices, with phase singularities appearing in the wake of the drifting structure. Localized structures are obtained in a light-valve experiment and made to drift by a mirror tilt in the feedback loop. Pairs of oppositely charged vortices are detected for small drifts, whereas for large drifts a vortex array develops. Observations are supported by numerical simulations and linear stability analysis of the system equations and are expected to be generic for a large class of translated optical patterns.

  16. A convexity preserving scheme for conservative advection transport

    NASA Astrophysics Data System (ADS)

    Xiao, Feng; Peng, Xindong

    2004-08-01

    A simple and practical scheme for advection transport equation is presented. The scheme, namely piecewise rational method (PRM), is a variant of the existing piecewise parabolic method (PPM) of Colella and Woodward (1984). Instead of the parabolic function, a rational function is used for the reconstruction. Making use of the convexity preserving nature of the rational function enables us to obtain oscillation-less numerical solutions, but avoids the adjustments of the cell-interface values to enforce the monotonicity in PPM. The PRM is very simple and computationally efficient. Our numerical results show that PRM is competitive to the PPM in many aspects, such as numerical accuracy and shape-preserving property.

  17. Self-advection of density perturbations on a sloping continental shelf

    SciTech Connect

    Ping-Tung Shaw; Csanady, G.T.

    1983-05-01

    Bottom water movement on the continental shelf is modeled by the nonlinear interaction between longshore bottom geostrophic flow and the density field. Bottom geostrophic velocity, subject to linear steady momentum equations with linear bottom friction, can be generated by along-isobath density variations over a sloping bottom. At the same time, the density field is slowly advected by the velocity field. Away from boundary layers, the interplay is governed by Burgers' equation, which shows the formation and self-propulsion of strong density gradients along an isobath. The direction of propagation of a dense water blob is to have shallow water on the right- (left-) hand side facing downstream in the Northern (Southern) Hemisphere. The propagation of a light water blob is opposite to that of a dense water blob.

  18. Thermo-chemical convection in planetary mantles: advection methods and magma ocean overturn simulations

    NASA Astrophysics Data System (ADS)

    Plesa, A.-C.; Tosi, N.; Hüttig, C.

    2012-04-01

    Thermal and chemical convection in planetary mantles are the most dominant dynamical processes influencing the thermal and geological evolution of a planet. After the planetary formation, convection in the interior is one of the most prominent processes being responsible for the heat transport efficiency, the interior structure, the magnetic field generation and the geological structures at the surface of a planet such as volcanoes, rifts and others. The slow creep of the silicate materials that make up the mantle of terrestrial planets (i.e. Mercury, Venus, the Earth and Mars) is driven by a combination of thermal and compositional buoyancy. On the one hand, the primordial heat accumulated after accretion and core formation and the heat released by the decay of radiogenic isotopes are transported from the interior to the surface by thermal convection. This process involves the transfer of heat both via diffusion, which occurs mainly across thermal boundary layers, and advection due to fluid motion in the bulk of the mantle. On the other hand, density anomalies of non-thermal origin associated with chemical (i.e. compositional) heterogeneities provide an additional source of buoyancy that actively contributes to the transport of energy and mass. In the present work we discuss the modeling of active compositional fields in the framework of solid-state mantle convection using the 3D spherical/2D cylindrical code Gaia [1, 2]. Numerical methods for the advection of active compositional fields fall in two main categories [3, 4]. They are based either on a fixed computational grid (Eulerian methods) or on evolving grids or moving particles (Lagrangian methods). We compare an Eulerian method based on double-diffusive convection against a Lagrangian, particle-based method. Though straightforward, the first method generally suffers from non-negligible numerical diffusion and demands then the use of grids with a high resolution. Moreover, its accuracy can substantially

  19. Rapid aqueous phase SO2 oxidation in winter fog in the Indo-Gangetic Plain

    NASA Astrophysics Data System (ADS)

    Sachan, Himanshu; Sarkar, Chinmoy; Sinha, Baerbel

    2013-04-01

    Sulphate and sulphur dioxide play an important role in environmental chemistry and climate. The majority of anthropogenic sulphur is released directly as SO2, and a significant fraction of biogenic and natural sulphur emissions are also either directly released as SO2 or oxidised to SO2 in the atmosphere (e.g. H2S, OCS, DMS). Around 50% of global atmospheric sulphur dioxide is then oxidised to sulphate, while the rest is lost through dry and wet deposition. The pathway by which SO2 is oxidised to sulphate is critical in determining the climate forcing and environmental effects of sulphate. Gas-phase oxidation of SO2 by OH radicals or criegee intermediates produces H2SO4 (g), which plays an important role in controlling new particle formation in the troposphere and also modifies the surface properties of hydrophobic particles such as soot and mineral dust. Heterogeneous oxidation of SO2 is considered to occur primarily in cloud droplets, although oxidation on sea salt aerosols and mineral dust surfaces are considered to be regionally important. Heterogeneous oxidation leads to the formation of fewer and larger particles with shorter atmospheric lifetime. The major oxidation pathways which are considered to contribute to sulphate formation in the aqueous phase are oxidation by H2O2 and oxidation by O3 and the lifetime of SO2 with respect to all known loss processes combined is considered to be 1-2 days. Here we report measurements of SO2 measurements from IISER Mohali - Ambient Air Quality Station (30.67°N, 76.73°E), a station located at a suburban site in the Indo Gangetic Basin (IGB) during wintertime (10th Dec. 2011 to 29th Feb. 2012). We use a strong point source of SO2 with known SO2/CO emission ratio (brick kiln) located 6.5 km east of our measurement site to estimate the loss rate of SO2 in wintertime fog in the IGB. We consider the transport from the source to the receptor site to be Lagrangian and use the measured CO concentration at the receptors site to

  20. 76 FR 44906 - Foremost 4809-ES Insect-O-Fog; Amended Cancellation Order

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-27

    ... 4809-ES Insect-O-Fog; Amended Cancellation Order AGENCY: Environmental Protection Agency (EPA). ACTION...), of an amended cancellation order for the pesticide product Foremost 4809-ES Insect-O-Fog, a pesticide product containing Piperonyl Butoxide and Pyrethrins. The registrant of Foremost 4809-ES...

  1. Can we estimate the fog-top height from atmospheric turbulent measurements at surface?

    NASA Astrophysics Data System (ADS)

    Román-Cascón, Carlos; Yagüe, Carlos; Steeneveld, Gert-Jan; Sastre, Mariano; Arrillaga, Jon A.; Maqueda, Gregorio

    2016-04-01

    The knowledge of the fog-top height (fog thickness) can be very meaningful for aircraft maneuvers, data assimilation/validation of Numerical Weather Prediction models or nowcasting of fog dissipation. However, its value is usually difficult to determine and it is sometimes approximated with satellite data, ground remote-sensing instruments or atmospheric soundings. These instruments are expensive and their data not always available. In this work, we show how the fog-top height shows a linear correlation with atmospheric turbulent variables measured close to the surface. This relation is statistically calculated from observational data of several radiation-fog events at two research sites: The Research Centre for the Lower Atmosphere (CIBA) in Spain and the Cabauw Experimental Site for Atmospheric Research (CESAR) in The Netherlands. Thus, surface friction velocity and buoyancy heat flux are presented as potential indicators of fog thickness. These methods are also evaluated over a long-lasting radiation-fog event at CESAR. The proposed methods could be operationally implemented for providing a continuous estimation of fog-top height through the deployment of a sonic anemometer close to the surface.

  2. Chemical Composition of Sea Fog Water Along the South China Sea

    NASA Astrophysics Data System (ADS)

    Yue, Yanyu; Niu, Shengjie; Zhao, Lijuan; Zhang, Yu; Xu, Feng

    2012-12-01

    The chemical and microphysical properties of sea fog were measured during a field experiment on Donghai Island, Zhanjiang of China from March 15 to April 18, 2010. The average pH and electrical conductivity (EC) value of the six sea fog cases during the experiment was 5.2 and 1,884 μS/cm. The observed total ion concentration of sea fog was four orders of magnitude higher than those in the North Pacific and other sea areas of China. The dominant anion and cation in all sea fog water samples were Cl- and Na+, respectively. From backward trajectory analysis and ion loading computation, it can be concluded that the ions in the samples were transported either from pollutants in distant industrial cities or from local ion deposition processes. The concentration of Ca2+ in the sea fog water samples in Case 2 suggested that a dust storm in the Inner Mongolia, a northern region of China several thousand kilometers away, could reach the South China Sea. The data also showed that the sea fog droplet spectrum over the South China Sea is unimodal. Through relationship analysis, it is illustrated that the evolution of microphysics (such as droplet concentration, diameter, and liquid water content) during fog process could affect the chemical properties of sea fog.

  3. 49 CFR 393.24 - Requirements for head lamps, auxiliary driving lamps and front fog lamps.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... of the required headlamps. Auxiliary driving lamps shall meet SAE Standard J581 Auxiliary Upper Beam Lamps, July 2004, and front fog lamps shall meet SAE Standard J583 Front Fog Lamp, August 2004. (See... specifications in FMVSS No. 108 (49 CFR 571.108), SAE J581, and SAE J583, respectively. [70 FR 48046, Aug....

  4. 49 CFR 393.24 - Requirements for head lamps, auxiliary driving lamps and front fog lamps.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... of the required headlamps. Auxiliary driving lamps shall meet SAE Standard J581 Auxiliary Upper Beam Lamps, July 2004, and front fog lamps shall meet SAE Standard J583 Front Fog Lamp, August 2004. (See... specifications in FMVSS No. 108 (49 CFR 571.108), SAE J581, and SAE J583, respectively....

  5. 1995 Integrated Monitoring Study: Fog measurements in the Southern San Joaquin Valley - preliminary results

    SciTech Connect

    Collett, J. Jr.; Bator, A.; Sherman, D.E.

    1996-12-31

    Fogs were sampled at three ground-based stations in the southern portion of California`s San Joaquin Valley as part of the winter component of the 1995 Integrated Monitoring Study (IMS95). The three sampling sites included two urban locations (Bakersfield and Fresno) and one rural location (near the Kern Wildlife Refuge). Both bulk and drop size-fractionated samples were collected at each site. Several fog events were sampled, with three periods of extensive fog coverage that included all three sampling sites. Results of preliminary data analysis are presented. Fog collected at the sites was generally quite basic. Most bulk fog samples had pH values above 6 reflecting strong inputs from ammonia. Occasional strong sulfur plumes at Bakersfield, however, tended to lower the fog pH. Aside from these periods, nitrate was generally present at much higher concentrations in the fog than sulfate. Decreases in fogwater loadings of major species over the course of one extended fog episode at Fresno suggest significant deposition was occurring to the surface, consistent with observations of substantial droplet fluxes to exposed surfaces during that period. 16 refs., 7 figs., 1 tab.

  6. Characterization of mineral particles in winter fog of Beijing analyzed by TEM and SEM.

    PubMed

    Li, Weijun; Shao, Longyi

    2010-02-01

    Aerosol samples were collected during winter fog and nonfog episodes in Beijing. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were applied to study morphologies, sizes, and compositions of aerosol particles. TEM observation indicates that most mineral particles collected in fog episode are scavenged in fog droplets. Number-size distributions of mineral particles collected in fog and nonfog episodes show two main peaks at the ranges of 0.1-0.3 and 1-2.5 microm, respectively. Based on their major compositions, mineral particles mainly include Si-rich, Ca-rich, and S-rich. Average S/Ca ratio of mineral particles collected in fog episode is 6.11, being eight times higher than that in nonfog episodes. Development mechanism of individual mineral particles in fog droplets is proposed. It is suggested that mineral particles with abundant alkaline components (e.g., "Ca-rich" particles) occurred in air should alleviate acidic degree of fog and contribute to complexity of fog droplets in Beijing.

  7. Acute exposure to realistic acid fog: Effects on respiratory function and airway responsiveness in asthmatics

    SciTech Connect

    Leduc, D.; De Vuyst, P.; Yernault, J.C.

    1995-11-01

    The biological effects of acid fog composed primarily of ammonium ions and sulfate are described. Subjects with asthma were exposed for one hour to sulfuric acid aerosol. Significant changes were not observed. Other asthma subjects were exposed to acid fog containing sulfate and ammonium ions. Again, pulmonary and bronchial function were not modified after inhalation.

  8. Asymmetric ratchet effect for directional transport of fog drops on static and dynamic butterfly wings.

    PubMed

    Liu, Chengcheng; Ju, Jie; Zheng, Yongmei; Jiang, Lei

    2014-02-25

    Inspired by novel creatures, researchers have developed varieties of fog drop transport systems and made significant contributions to the fields of heat transferring, water collecting, antifogging, and so on. Up to now, most of the efforts in directional fog drop transport have been focused on static surfaces. Considering it is not practical to keep surfaces still all the time in reality, conducting investigations on surfaces that can transport fog drops in both static and dynamic states has become more and more important. Here we report the wings of Morpho deidamia butterflies can directionally transport fog drops in both static and dynamic states. This directional drop transport ability results from the micro/nano ratchet-like structure of butterfly wings: the surface of butterfly wings is composed of overlapped scales, and the scales are covered with porous asymmetric ridges. Influenced by this special structure, fog drops on static wings are transported directionally as a result of the fog drops' asymmetric growth and coalescence. Fog drops on vibrating wings are propelled directionally due to the fog drops' asymmetric dewetting from the wings.

  9. Horizontal advection, diffusion and plankton spectra at the sea surface.

    NASA Astrophysics Data System (ADS)

    Bracco, A.; Clayton, S.; Pasquero, C.

    2009-04-01

    Plankton patchiness is ubiquitous in the oceans, and various physical and biological processes have been proposed as its generating mechanisms. However, a coherent statement on the problem is missing, due to both a small number of suitable observations and to an incomplete understanding of the properties of reactive tracers in turbulent media. Abraham (1998) suggested that horizontal advection may be the dominant process behind the observed distributions of phytoplankton and zooplankton, acting to mix tracers with longer reaction times (Rt) down to smaller scales. Conversely, Mahadevan and Campbell (2002) attributed the relative distributions of sea surface temperature and phytoplankton to small scale upwelling, where tracers with longer Rt are able to homogenize more than those with shorter reaction times. Neither of the above mechanisms can explain simultaneously the (relative) spectral slopes of temperature, phytoplankton and zooplankton. Here, with a simple advection model and a large suite of numerical experiments, we concentrate on some of the physical processes influencing the relative distributions of tracers at the ocean surface, and we investigate: 1) the impact of the spatial scale of tracer supply; 2) the role played by coherent eddies on the distribution of tracers with different Rt; 3) the role of diffusion (so far neglected). We show that diffusion determines the distribution of temperature, regardless of the nature of the forcing. We also find that coherent structures together with differential diffusion of tracers with different Rt impact the tracer distributions. This may help in understanding the highly variable nature of observed plankton spectra.

  10. Advection-Based Sparse Data Management for Visualizing Unsteady Flow.

    PubMed

    Guo, Hanqi; Zhang, Jiang; Liu, Richen; Liu, Lu; Yuan, Xiaoru; Huang, Jian; Meng, Xiangfei; Pan, Jingshan

    2014-12-01

    When computing integral curves and integral surfaces for large-scale unsteady flow fields, a major bottleneck is the widening gap between data access demands and the available bandwidth (both I/O and in-memory). In this work, we explore a novel advection-based scheme to manage flow field data for both efficiency and scalability. The key is to first partition flow field into blocklets (e.g. cells or very fine-grained blocks of cells), and then (pre)fetch and manage blocklets on-demand using a parallel key-value store. The benefits are (1) greatly increasing the scale of local-range analysis (e.g. source-destination queries, streak surface generation) that can fit within any given limit of hardware resources; (2) improving memory and I/O bandwidth-efficiencies as well as the scalability of naive task-parallel particle advection. We demonstrate our method using a prototype system that works on workstation and also in supercomputing environments. Results show significantly reduced I/O overhead compared to accessing raw flow data, and also high scalability on a supercomputer for a variety of applications.

  11. Local and nonlocal advection of a passive scalar

    NASA Astrophysics Data System (ADS)

    Scott, R. K.

    2006-11-01

    Passive and active scalar mixing is examined in a simple one-parameter family of two-dimensional flows based on quasi-geostrophic dynamics, in which the active scalar, the quasi-geostrophic potential vorticity, is confined to a single horizontal surface (so-called surface quasi-geostrophic dynamics) and in which a passive scalar field is also advected by the (horizontal, two-dimensional) velocity field at a finite distance from the surface. At large distances from the surface the flow is determined by the largest horizontal scales, the flow is spectrally nonlocal, and a chaotic advection-type regime dominates. At small distances, z, scaling arguments suggest a transition wavenumber kc˜1/2z, where the slope of the passive scalar spectrum changes from k-5/3, determined by local dynamics, to k-1, determined by nonlocal dynamics, analogous to the transition to a k-1 slope in the Batchelor regime in three-dimensional turbulence. Direct numerical simulations reproduce the qualitative aspects of this transition. Other characteristics of the simulated scalar fields, such as the relative dominance of coherent or filamentary structures, are also shown to depend strongly on the degree of locality.

  12. THE ADVECTION OF SUPERGRANULES BY THE SUN'S AXISYMMETRIC FLOWS

    SciTech Connect

    Hathaway, David H.; Williams, Peter E.; Rosa, Kevin Dela; Cuntz, Manfred E-mail: peter.williams@nasa.go

    2010-12-10

    We show that the motions of supergranules are consistent with a model in which they are simply advected by the axisymmetric flows in the Sun's surface shear layer. We produce a 10 day series of simulated Doppler images at a 15 minute cadence that reproduces most spatial and temporal characteristics seen in the SOHO/MDI Doppler data. Our simulated data have a spectrum of cellular flows with just two components-a granule component that peaks at spherical wavenumbers of about 4000 and a supergranule component that peaks at wavenumbers of about 110. We include the advection of these cellular components by the axisymmetric flows-differential rotation and meridional flow-whose variations with latitude and depth (wavenumber) are consistent with observations. We mimic the evolution of the cellular pattern by introducing random variations to the phases of the spectral components at rates that reproduce the levels of cross-correlation as functions of time and latitude. Our simulated data do not include any wave-like characteristics for the supergranules yet can reproduce the rotation characteristics previously attributed to wave-like behavior. We find rotation rates which appear faster than the actual rotation rates and attribute this to projection effects. We find that the measured meridional flow does accurately represent the actual flow and that the observations indicate poleward flow to 65{sup 0}-70{sup 0} latitude with equatorward countercells in the polar regions.

  13. Space-fractional advection-diffusion and reflective boundary condition.

    PubMed

    Krepysheva, Natalia; Di Pietro, Liliana; Néel, Marie-Christine

    2006-02-01

    Anomalous diffusive transport arises in a large diversity of disordered media. Stochastic formulations in terms of continuous time random walks (CTRWs) with transition probability densities showing space- and/or time-diverging moments were developed to account for anomalous behaviors. A broad class of CTRWs was shown to correspond, on the macroscopic scale, to advection-diffusion equations involving derivatives of noninteger order. In particular, CTRWs with Lévy distribution of jumps and finite mean waiting time lead to a space-fractional equation that accounts for superdiffusion and involves a nonlocal integral-differential operator. Within this framework, we analyze the evolution of particles performing symmetric Lévy flights with respect to a fluid moving at uniform speed . The particles are restricted to a semi-infinite domain limited by a reflective barrier. We show that the introduction of the boundary condition induces a modification in the kernel of the nonlocal operator. Thus, the macroscopic space-fractional advection-diffusion equation obtained is different from that in an infinite medium.

  14. Effects of demographic stochasticity on population persistence in advective media.

    PubMed

    Kolpas, Allison; Nisbet, Roger M

    2010-07-01

    Many populations live and disperse in advective media. A fundamental question, known as the "drift paradox" in stream ecology, is how a closed population can survive when it is constantly being transported downstream by the flow. Recent population-level models have focused on the role of diffusive movement in balancing the effects of advection, predicting critical conditions for persistence. Here, we formulate an individual-based stochastic analog of the model described in (Lutscher et al., SIAM Rev. 47(4):749-772, 2005) to quantify the effects of demographic stochasticity on persistence. Population dynamics are modeled as a logistic growth process and dispersal as a position-jump process on a finite domain divided into patches. When there is no correlation in the interpatch movement of residents, stochasticity simply smooths the persistence-extinction boundary. However, when individuals disperse in "packets" from one patch to another and the flow field is memoryless on the timescale of packet transport, the probability of persistence is greatly enhanced. The latter transport mechanism may be characteristic of larval dispersal in the coastal ocean or wind-dispersed seed pods.

  15. Transient responses to spatial perturbations in advective systems.

    PubMed

    Anderson, Kurt E; Nisbet, Roger M; McCauley, Edward

    2008-07-01

    We study the transient dynamics, following a spatially-extended perturbation of models describing populations residing in advective media such as streams and rivers. Our analyses emphasize metrics that are independent of initial perturbations-resilience, reactivity, and the amplification envelope-and relate them to component spatial wavelengths of the perturbation using spatial Fourier transforms of the state variables. This approach offers a powerful way of understanding the influence of spatial scale on the initial dynamics of a population following a spatially variable environmental perturbation, an important property in determining the ecological implications of transient dynamics in advective systems. We find that asymptotically stable systems may exhibit transient amplification of perturbations (i.e., have positive reactivity) for some spatial wavelengths and not others. Furthermore, the degree and duration of amplification varies strongly with spatial wavelength. For two single-population models, there is a relationship between transient dynamics and the response length that characterizes the steady state response to spatial perturbations: a long response length implies that peak amplification of perturbations is small and occurs fast. This relationship holds less generally in a specialist consumer-resource model, likely due to the model's tendency for flow-induced instabilities at an alternative characteristic spatial scale.

  16. A cryogenic circulating advective multi-pass absorption cell

    NASA Astrophysics Data System (ADS)

    Stockett, M. H.; Lawler, J. E.

    2012-03-01

    A novel absorption cell has been developed to enable a spectroscopic survey of a broad range of polycyclic aromatic hydrocarbons (PAH) under astrophysically relevant conditions and utilizing a synchrotron radiation continuum to test the still controversial hypothesis that these molecules or their ions could be carriers of the diffuse interstellar bands. The cryogenic circulating advective multi-pass absorption cell resembles a wind tunnel; molecules evaporated from a crucible or injected using a custom gas feedthrough are entrained in a laminar flow of cryogenically cooled buffer gas and advected into the path of the synchrotron beam. This system includes a multi-pass optical White cell enabling absorption path lengths of hundreds of meters and a detection sensitivity to molecular densities on the order of 107 cm-3. A capacitively coupled radio frequency dielectric barrier discharge provides ionized and metastable buffer gas atoms for ionizing the candidate molecules via charge exchange and the Penning effect. Stronger than expected clustering of PAH molecules has slowed efforts to record gas phase PAH spectra at cryogenic temperatures, though such clusters may play a role in other interstellar phenomena.

  17. A cryogenic circulating advective multi-pass absorption cell.

    PubMed

    Stockett, M H; Lawler, J E

    2012-03-01

    A novel absorption cell has been developed to enable a spectroscopic survey of a broad range of polycyclic aromatic hydrocarbons (PAH) under astrophysically relevant conditions and utilizing a synchrotron radiation continuum to test the still controversial hypothesis that these molecules or their ions could be carriers of the diffuse interstellar bands. The cryogenic circulating advective multi-pass absorption cell resembles a wind tunnel; molecules evaporated from a crucible or injected using a custom gas feedthrough are entrained in a laminar flow of cryogenically cooled buffer gas and advected into the path of the synchrotron beam. This system includes a multi-pass optical White cell enabling absorption path lengths of hundreds of meters and a detection sensitivity to molecular densities on the order of 10(7) cm(-3). A capacitively coupled radio frequency dielectric barrier discharge provides ionized and metastable buffer gas atoms for ionizing the candidate molecules via charge exchange and the Penning effect. Stronger than expected clustering of PAH molecules has slowed efforts to record gas phase PAH spectra at cryogenic temperatures, though such clusters may play a role in other interstellar phenomena.

  18. Observation of Magnetic Reconnection Driven by Granular Scale Advection

    NASA Astrophysics Data System (ADS)

    Zeng, Zhichen; Cao, W.; Ji, H.

    2013-07-01

    We report the first evidence of magnetic reconnection driven by advection in a rapidly developing large granule, using high spatial resolution observations of a small surge event (base size 4‧‧ by 4‧‧) with the 1.6 meter aperture New Solar Telescope (NST) at Big Bear Solar Observatory. The observations were carried out in narrow-band (0.5 Å) Helium I 10830 Å and broad-band (10 Å) TiO 7057 Å. Since He I 10830 Å triplet has very high excitation level and is optically thin, its filtergrams enable us to investigate the surge from the photosphere through the chromosphere into the lower corona. Simultaneous space data from Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) were used in the analysis. It is shown that the surge is spatio-temporally associated with magnetic flux emergence in the rapidly developing large granule. During the development of the granule, its advecting flow ( 2 km/ s) squeezed the magnetic flux into an intergranular lane area, where a magnetic flux concentration was formed and the neighboring flux with opposite magnetic polarity was cancelled. During the cancellation, the surge was produced as absorption in He I 10830 Å filtergrams while simultaneous EUV brightening occurred at its base. The observations clearly indicate evidence of finest-scale reconnection process driven by the granule’s motion.

  19. Observation of Magnetic Reconnection Driven by Granular Scale Advection

    NASA Astrophysics Data System (ADS)

    Zeng, Zhicheng; Cao, Wenda; Ji, Haisheng

    2013-06-01

    We report the first evidence of magnetic reconnection driven by advection in a rapidly developing large granule using high spatial resolution observations of a small surge event (base size ~ 4'' × 4'') with the 1.6 m aperture New Solar Telescope at the Big Bear Solar Observatory. The observations were carried out in narrowband (0.5 Å) He I 10830 Å and broadband (10 Å) TiO 7057 Å. Since He I 10830 Å triplet has a very high excitation level and is optically thin, its filtergrams enable us to investigate the surge from the photosphere through the chromosphere into the lower corona. Simultaneous space data from the Atmospheric Imaging Assembly and Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory were used in the analysis. It is shown that the surge is spatio-temporally associated with magnetic flux emergence in the rapidly developing large granule. During the development of the granule, its advecting flow (~2 km s-1) squeezed the magnetic flux into an intergranular lane area, where a magnetic flux concentration was formed and the neighboring flux with opposite magnetic polarity was canceled. During the cancellation, the surge was produced as absorption in He I 10830 Å filtergrams while simultaneous EUV brightening occurred at its base. The observations clearly indicate evidence of a finest-scale reconnection process driven by the granule's motion.

  20. Positivity-preserving numerical schemes for multidimensional advection

    NASA Technical Reports Server (NTRS)

    Leonard, B. P.; Macvean, M. K.; Lock, A. P.

    1993-01-01

    This report describes the construction of an explicit, single time-step, conservative, finite-volume method for multidimensional advective flow, based on a uniformly third-order polynomial interpolation algorithm (UTOPIA). Particular attention is paid to the problem of flow-to-grid angle-dependent, anisotropic distortion typical of one-dimensional schemes used component-wise. The third-order multidimensional scheme automatically includes certain cross-difference terms that guarantee good isotropy (and stability). However, above first-order, polynomial-based advection schemes do not preserve positivity (the multidimensional analogue of monotonicity). For this reason, a multidimensional generalization of the first author's universal flux-limiter is sought. This is a very challenging problem. A simple flux-limiter can be found; but this introduces strong anisotropic distortion. A more sophisticated technique, limiting part of the flux and then restoring the isotropy-maintaining cross-terms afterwards, gives more satisfactory results. Test cases are confined to two dimensions; three-dimensional extensions are briefly discussed.

  1. A cryogenic circulating advective multi-pass absorption cell

    SciTech Connect

    Stockett, M. H.; Lawler, J. E.

    2012-03-15

    A novel absorption cell has been developed to enable a spectroscopic survey of a broad range of polycyclic aromatic hydrocarbons (PAH) under astrophysically relevant conditions and utilizing a synchrotron radiation continuum to test the still controversial hypothesis that these molecules or their ions could be carriers of the diffuse interstellar bands. The cryogenic circulating advective multi-pass absorption cell resembles a wind tunnel; molecules evaporated from a crucible or injected using a custom gas feedthrough are entrained in a laminar flow of cryogenically cooled buffer gas and advected into the path of the synchrotron beam. This system includes a multi-pass optical White cell enabling absorption path lengths of hundreds of meters and a detection sensitivity to molecular densities on the order of 10{sup 7} cm{sup -3}. A capacitively coupled radio frequency dielectric barrier discharge provides ionized and metastable buffer gas atoms for ionizing the candidate molecules via charge exchange and the Penning effect. Stronger than expected clustering of PAH molecules has slowed efforts to record gas phase PAH spectra at cryogenic temperatures, though such clusters may play a role in other interstellar phenomena.

  2. Chaotic advection in 2D anisotropic porous media

    NASA Astrophysics Data System (ADS)

    Varghese, Stephen; Speetjens, Michel; Trieling, Ruben; Toschi, Federico

    2015-11-01

    Traditional methods for heat recovery from underground geothermal reservoirs employ a static system of injector-producer wells. Recent studies in literature have shown that using a well-devised pumping scheme, through actuation of multiple injector-producer wells, can dramatically enhance production rates due to the increased scalar / heat transport by means of chaotic advection. However the effect of reservoir anisotropy on kinematic mixing and heat transport is unknown and has to be incorporated and studied for practical deployment in the field. As a first step, we numerically investigate the effect of anisotropy (both magnitude and direction) on (chaotic) advection of passive tracers in a time-periodic Darcy flow within a 2D circular domain driven by periodically reoriented diametrically opposite source-sink pairs. Preliminary results indicate that anisotropy has a significant impact on the location, shape and size of coherent structures in the Poincare sections. This implies that the optimal operating parameters (well spacing, time period of well actuation) may vary strongly and must be carefully chosen so as to enhance subsurface transport. This work is part of the research program of the Foundation for Fundamental Research on Matter (FOM), which is part of Netherlands Organisation for Scientific Research (NWO). This research program is co-financed by Shell Global Solutions International B.V.

  3. Fog and Cloud Induced Aerosol Modification Observed by AERONET

    NASA Technical Reports Server (NTRS)

    Eck, T. F.; Holben, B. N.; Reid, J. S.; Giles, D. M.; Rivas, M. A.; Singh, R. P.; Tripathi, S. N.; Bruegge, C. J.; Platnick, S. E.; Arnold, G. T.; Krotkov, N. A.; Carn, S. A.; Sinyuk, A.; Dubovik, O.; Arola, A.; Schafer, J. S.; Artaxo, P.; Smirnov, A.; Chen, H.; Goloub, P.

    2011-01-01

    Large fine mode (sub-micron radius) dominated aerosols in size distributions retrieved from AERONET have been observed after fog or low-altitude cloud dissipation events. These column-integrated size distributions have been obtained at several sites in many regions of the world, typically after evaporation of low altitude cloud such as stratocumulus or fog. Retrievals with cloud processed aerosol are sometimes bimodal in the accumulation mode with the larger size mode often approx.0.4 - 0.5 microns radius (volume distribution); the smaller mode typically approx.0.12 to aprrox.0.20 microns may be interstitial aerosol that were not modified by incorporation in droplets and/or aerosol that are less hygroscopic in nature. Bimodal accumulation mode size distributions have often been observed from in situ measurements of aerosols that have interacted with clouds, and AERONET size distribution retrievals made after dissipation of cloud or fog are in good agreement with particle sizes measured by in situ techniques for cloud-processed aerosols. Aerosols of this type and large size range (in lower concentrations) may also be formed by cloud processing in partly cloudy conditions and may contribute to the shoulder of larger size particles in the accumulation mode retrievals, especially in regions where sulfate and other soluble aerosol are a significant component of the total aerosol composition. Observed trends of increasing aerosol optical depth (AOD) as fine mode radius increased suggests higher AOD in the near cloud environment and therefore greater aerosol direct radiative forcing than typically obtained from remote sensing, due to bias towards sampling at low cloud fraction.

  4. FOG-2 mediated recruitment of the NuRD complex regulates cardiomyocyte proliferation during heart development.

    PubMed

    Garnatz, Audrey S; Gao, Zhiguang; Broman, Michael; Martens, Spencer; Earley, Judy U; Svensson, Eric C

    2014-11-01

    FOG-2 is a multi-zinc finger protein that binds the transcriptional activator GATA4 and modulates GATA4-mediated regulation of target genes during heart development. Our previous work has demonstrated that the Nucleosome Remodeling and Deacetylase (NuRD) complex physically interacts with FOG-2 and is necessary for FOG-2 mediated repression of GATA4 activity in vitro. However, the relevance of this interaction for FOG-2 function in vivo has remained unclear. In this report, we demonstrate the importance of FOG-2/NuRD interaction through the generation and characterization of mice homozygous for a mutation in FOG-2 that disrupts NuRD binding (FOG-2(R3K5A)). These mice exhibit a perinatal lethality and have multiple cardiac malformations, including ventricular and atrial septal defects and a thin ventricular myocardium. To investigate the etiology of the thin myocardium, we measured the rate of cardiomyocyte proliferation in wild-type and FOG-2(R3K5A) developing hearts. We found cardiomyocyte proliferation was reduced by 31±8% in FOG-2(R3K5A) mice. Gene expression analysis indicated that the cell cycle inhibitor Cdkn1a (p21(cip1)) is up-regulated 2.0±0.2-fold in FOG-2(R3K5A) hearts. In addition, we demonstrate that FOG-2 can directly repress the activity of the Cdkn1a gene promoter, suggesting a model by which FOG-2/NuRD promotes ventricular wall thickening by repression of this cell cycle inhibitor. Consistent with this notion, the genetic ablation of Cdkn1a in FOG-2(R3K5A) mice leads to an improvement in left ventricular function and a partial rescue of left ventricular wall thickness. Taken together, our results define a novel mechanism in which FOG-2/NuRD interaction is required for cardiomyocyte proliferation by directly down-regulating the cell cycle inhibitor Cdkn1a during heart development.

  5. A multi-structural and multi-functional integrated fog collection system in cactus

    PubMed Central

    Ju, Jie; Bai, Hao; Zheng, Yongmei; Zhao, Tianyi; Fang, Ruochen; Jiang, Lei

    2012-01-01

    Multiple biological structures have demonstrated fog collection abilities, such as beetle backs with bumps and spider silks with periodic spindle-knots and joints. Many Cactaceae species live in arid environments and are extremely drought-tolerant. Here we report that one of the survival systems of the cactus Opuntia microdasys lies in its efficient fog collection system. This unique system is composed of well-distributed clusters of conical spines and trichomes on the cactus stem; each spine contains three integrated parts that have different roles in the fog collection process according to their surface structural features. The gradient of the Laplace pressure, the gradient of the surface-free energy and multi-function integration endow the cactus with an efficient fog collection system. Investigations of the structure–function relationship in this system may help us to design novel materials and devices to collect water from fog with high efficiencies. PMID:23212376

  6. Effects of acid fog on airway function in people with asthma. Final report

    SciTech Connect

    Sheppard, D.; Balmes, J.R.; Christian, D.

    1988-11-30

    The study was built on earlier work examining the effects of acidic fog on human subjects with asthma. Mouthpiece exposure studies on asthmatic subjects showed that both nitric and sulfuric acids potentiate the bronchoconstrictor effects of fog water, and that these acids appear to be similar in this respect. The work resulted in the exposure chamber at the University of California, San Francisco being extensively modified, based on improvements recommended in an earlier investigation, thus allowing human subjects to be exposed to rigorously controlled and monitored test fogs. The study used the chamber to first examine the effects of fog without acid, and then the effects of fog with acid, on exercising subjects with asthma.

  7. A multi-structural and multi-functional integrated fog collection system in cactus.

    PubMed

    Ju, Jie; Bai, Hao; Zheng, Yongmei; Zhao, Tianyi; Fang, Ruochen; Jiang, Lei

    2012-01-01

    Multiple biological structures have demonstrated fog collection abilities, such as beetle backs with bumps and spider silks with periodic spindle-knots and joints. Many Cactaceae species live in arid environments and are extremely drought-tolerant. Here we report that one of the survival systems of the cactus Opuntia microdasys lies in its efficient fog collection system. This unique system is composed of well-distributed clusters of conical spines and trichomes on the cactus stem; each spine contains three integrated parts that have different roles in the fog collection process according to their surface structural features. The gradient of the Laplace pressure, the gradient of the surface-free energy and multi-function integration endow the cactus with an efficient fog collection system. Investigations of the structure-function relationship in this system may help us to design novel materials and devices to collect water from fog with high efficiencies.

  8. Field evaluation of fog dispersal tests at Elmira, NY: Final report

    SciTech Connect

    Rogers, C.W.; Wattle, B.J.; Mack, E.J.

    1987-06-01

    Calspan Corp., under contract to Energy Innovations, Inc., assisted in tests of the EGD Fog Precipiation System at Elmira/Corning Regional Airport in New York during the summer/fall fog season of 1986 by conducting an independent, objective evaluation of the EGD System during these tests. Specifically, Calspan's role was to: Establish and maintain a network of ground-based visibility monitors and supporting meteorological instrumentation for measuring fog characteristics during EGD System tests at Elmira; provide weather forecasts of the potential for fog at Elmira during the summer-fall fog season; analyze visibility and surface wind velocity measurements to determine the efficacy of the EGD system in producing visibility improvement during dispersal tests; and provide a final independent summary report documenting experiment protocol and the results of Calspan's analyses. 2 refs., 12 figs., 6 tabs.

  9. Fog Water Systems in South Africa: An Update.

    NASA Astrophysics Data System (ADS)

    van Heerden, J.; Olivier, J.; van Schalkwyk, L.

    2010-07-01

    This paper reports on fog water harvesting in South Africa. Ten semi-operational fog water catchment systems were erected at rural schools in South Africa between 1999 and 2007. These systems copied the basic design features of the systems at El Tofo, Chili, modified for South African conditions. Major problems were experienced due to poor maintenance and vandalism. Another serious problem was the abrasion of the 40% shade cloth netting against the supporting cables. Gale force winds also led to the complete failure and collapse of the systems. It thus became obvious that the simple flat screen structure is not suitable for South African conditions. Co-operation with Mesh Concepts cc and Cloud Water Concepts cc resulted in the development of a new design for fog/cloud water collection. This design comprises three 40 m2 panels joined together to form the sides of an equilateral triangle. Four such triangles are linked together to form a 9 panel system. The six 6 m poles supporting the 9 panels are 11 m apart and all structure and net support cables are anchored, in line, with the sides of the panels. The system is 5.5 m high and the 9 panel system exposes 360m2 to the cloud/fog. The system is stable and wind forces are transferred to the anchors via nylon pulleys housed in brackets bolted to the poles. The mesh material is a poly yarn co-knitted with stainless steel that provides strength and stability to the mesh. An added advantage is that several 9 panel systems can be linked and expanded to cover the available space. There are currently three such systems in place - at Brook’s Nek (1650 m MSL) in the mountains of the Eastern Cape (684 m2) and at Lamberts Bay and Doring Bay (both 360 m2) on the West Coast. An experimental 3-panel system has been established on the Zondachsberg (1142m MSL), 35 km north of Plettenberg Bay. Preliminary data from this site indicate that orographic cloud forms against the mountain side soon after the wind turns to the south. Average

  10. Implementation of a Single-Column Model for Fog and Low Cloud Forecasting at Central-Spanish Airports

    NASA Astrophysics Data System (ADS)

    Terradellas, Enric; Cano, Darío

    2007-06-01

    Operations at Central-Spanish airports are often, especially in winter, affected by visibility reduction. The Instituto Nacional de Meteorología (INM), the Spanish Weather Service, has developed a single-column model (SCM) in order to improve short-term forecasts of fog, visibility and low-clouds. The SCM, called H1D, is a one-dimensional version of the HIRLAM limited-area model. It is operationally run for three airports in the region: Madrid-Barajas, Almagro and Albacete-Los Llanos. Since SCMs cannot deal with horizontal heterogeneity, the terms that depend on the horizontal structure of the atmosphere are estimated from the outputs of the three-dimensional (3-D) model and introduced into the SCM as external forcings. The systematic analysis of the meteorological situations has evidenced the existence of a close relationship between fog formation and the presence of drainage winds in the region. Since the 3-D model docs not have the necessary resolution to correctly simulate the main features of the drainage flow caused by the complex topography in the proximity of Madrid-Barajas, it cannot provide the SCM with the correct forcings. This problem has been partially overcome through the introduction of a module that, under certain conditions, substitutes the values computed from the 3-D model outputs by others that are based on a conceptual model of the phenomenon and have been empirically derived from climatological knowledge. This module improves the H1D verification scores for the basic meteorological variables—wind, temperature and humidity—and reduces the false alarm rate in fog forecast.

  11. Determining the Hydrological Importance of Coastal Fog in Northern California Using Stable Isotopes of Water

    NASA Astrophysics Data System (ADS)

    Scholl, M. A.; Torregrosa, A.; Coplen, T. B.

    2014-12-01

    Fog and cloud water can be an important part of the water cycle in mountainous coastal areas. In coastal California's Mediterranean climate, fog is the predominant precipitation source during the summer months. Here we report initial results of a study utilizing stable hydrogen and oxygen isotopes of water to investigate the role of fog in the hydrology of two ecosystems in Sonoma County, CA. The two study sites were the Bodega Marine Laboratory (BML) at 13 m elevation at the coast, and the Pepperwood Preserve at 375 m elevation in the North Coast Range, 44 km inland to the northeast. During a 1-week period in July 2014, fog samples were collected at 30-minute intervals using small active-strand cloudwater collectors (mini-CASCCs) and automated precipitation samplers. Four overnight fog events were collected at the Pepperwood site, while at the BML site, the liquid water content of the fog was very low, and only one cumulative sample was obtained. Groundwater samples from five wells and seven springs, and surface water samples from two streams were collected in and around the Pepperwood Preserve and on Bodega Head near BML. Droplet size distribution of the fog at BML was monitored, and at both sites, air temperature was measured at 10-minute intervals to assess variation in the δ 18O and δ 2H values of fog related to temperature. Relative humidity, wind speed, and wind direction were obtained from weather stations at each site. Previous work in this area (Coplen et al., in prep) documented the isotopic signatures of winter precipitation from frontal systems and landfalling Pacific storms. These results will be combined with the isotopic signature of summer fog water to determine whether fog contributes to shallow groundwater recharge or streamflow at the two sites.

  12. Fog-induced variations in aerosol optical and physical properties over the Indo-Gangetic Basin and impact to aerosol radiative forcing

    NASA Astrophysics Data System (ADS)

    Das, S. K.; Jayaraman, A.; Misra, A.

    2008-06-01

    A detailed study on the changes in aerosol physical and optical properties during fog events were made in December 2004 at Hissar (29.13° N, 75.70° E), a city located in the Indo-Gangetic basin. The visible aerosol optical depth was relatively low (0.3) during the initial days, which, however, increased (0.86) as the month progressed. The increasing aerosol amount, the decreasing surface temperature and a higher relative humidity condition were found favoring the formation of fog. The fog event is also found to alter the aerosol size distribution. An increase in the number concentration of the nucleation mode (radius<0.1 μm) particles, along with a decrease in the mode radius showed the formation of freshly nucleated aerosols. In the case of accumulation mode (0.1 μmfog event which prolongs longer into the daytime has a stronger effect on the diurnally averaged aerosol radiative forcing than those events which are confined only to the early morning hours.

  13. Thermally driven advection for radioxenon transport from an underground nuclear explosion

    NASA Astrophysics Data System (ADS)

    Sun, Yunwei; Carrigan, Charles R.

    2016-05-01

    Barometric pumping is a ubiquitous process resulting in migration of gases in the subsurface that has been studied as the primary mechanism for noble gas transport from an underground nuclear explosion (UNE). However, at early times following a UNE, advection driven by explosion residual heat is relevant to noble gas transport. A rigorous measure is needed for demonstrating how, when, and where advection is important. In this paper three physical processes of uncertain magnitude (oscillatory advection, matrix diffusion, and thermally driven advection) are parameterized by using boundary conditions, system properties, and source term strength. Sobol' sensitivity analysis is conducted to evaluate the importance of all physical processes influencing the xenon signals. This study indicates that thermally driven advection plays a more important role in producing xenon signals than oscillatory advection and matrix diffusion at early times following a UNE, and xenon isotopic ratios are observed to have both time and spatial dependence.

  14. Regional deposition of inhaled fog droplets: preliminary observations

    SciTech Connect

    Bowes, S.M. III; Laube, B.L.; Links, J.M.; Frank, R.

    1989-02-01

    The regional deposition of a monodisperse 10-micron mass median aerodynamic diameter fog was studied in four healthy adult male nonsmokers. The fog was radiolabeled with technetium-99m sulfur colloid to enable detection by an Anger camera of deposited activity in the following regions of the respiratory tract: oropharynx, larynx, trachea, and intrapulmonary airways. Intrapulmonary deposition was further analyzed by computer with inner, intermediate, and outer zones, and within apical, intermediate and basal zones of the right lung. The radiolabeled aerosol was inhaled by mouth through a face-mask with the nasal airway occluded. Respiratory frequency, tidal volume, and jaw position were controlled and were commensurate with the oral component of oronasal breathing during moderate exercise. Deposition in the larynx, trachea, and intrapulmonary airways was a function of the scrubbing efficiency of the oropharynx, which differed substantially among subjects, and ranged from 72 to 99%. The density of the aerosol deposit in the larynx probably exceeded that of any of the subdivisions of the tracheobronchial tree and lung. Within the lung, deposition favored the inner zone (assumed to contain the larger airways) over the outer zone (assumed to be dominated by smaller airways and alveoli). Intrapulmonary aerosol distribution in an elderly subject with borderline evidence of airway obstruction differed from that observed in younger subjects. The possible consequences of altered lung elastic recoil, as may occur with aging, for regional dosimetry is discussed.

  15. Research Spotlight: Lost in a fog on Mars

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2011-04-01

    A pair of cameras mounted on the back of the Phoenix Mars Lander were used to capture how laser light, emitted by the lander's light detection and ranging (lidar) system, was scattered by water ice in the red planet's thin atmosphere. Moores et al. used the unique technique during four nights in 2008 to give the first detailed profile of the ice water content in the Martian near-surface atmosphere. The authors found that the icy fog is thickest around 50 meters above the surface, with a maximum concentration of 1.7 milligrams per cubic meter. They also found that the fog is not uniform but tends to decrease in thickness toward the surface. As the Martian night wears on, the surface of the planet cools below the frost point and water vapor in the atmosphere gets deposited on the ground. As the atmosphere is mixed by turbulence, more water is brought to lower altitudes, adding to the growing frost layer. Ice crystals also form in the air and precipitate to the ground from successively higher altitudes. The researchers estimate that by the time the Sun starts to rise in the morning, 2.5 micrometers of snow and frost have coated the surface of Mars in the northerly region around the Phoenix Lander. (Geophysical Research Letters, doi:10.1029/2010GL046315, 2011)

  16. Unification of some advection schemes in two dimensions

    NASA Technical Reports Server (NTRS)

    Sidilkover, D.; Roe, P. L.

    1995-01-01

    The relationship between two approaches towards construction of genuinely two-dimensional upwind advection schemes is established. One of these approaches is of the control volume type applicable on structured cartesian meshes. It resulted in the compact high resolution schemes capable of maintaining second order accuracy in both homogeneous and inhomogeneous cases. Another one is the fluctuation splitting approach, which is well suited for triangular (and possibly) unstructured meshes. Understanding the relationship between these two approaches allows us to formulate here a new fluctuation splitting high resolution (i.e. possible use of artificial compression, while maintaining positivity property) scheme. This scheme is shown to be linearity preserving in inhomogeneous as well as homogeneous cases.

  17. Mobile scintillometry to study heat advection over heterogeneous surfaces

    NASA Astrophysics Data System (ADS)

    Kleissl, J.

    2007-12-01

    Large Aperture Scintillometer (LAS) receivers measure the structure parameter of the refractive index from intensity fluctuations of the transmitter beam. Due to the spatial averaging over 1-4 km employed by this emerging technique the constraints for long temporal averaging (15-30 min) and associated uncertainties that have to be met by other flux measurement techniques do not apply for LASs. In this paper the constraints for temporal averaging of LASs will be examined as a function of environmental conditions and transect geometry. Moreover, analysis of data from a mobile LAS measurement across a surface gradient from rough and dry to smoother and wet will be presented. In this experiment the LAS was mounted on a pickup truck, allowing for quick redeployment of the transect after meaurement. The potential for the use of LAS to study local advection of heat in riparian or irrigated areas in the semi-arid southwest will be evaluated.

  18. Dependence of advection-diffusion-reaction on flow coherent structures

    NASA Astrophysics Data System (ADS)

    Tang, Wenbo; Luna, Christopher

    2013-10-01

    A study on an advection-diffusion-reaction system is presented. Variability of the reaction process in such a system triggered by a highly localized source is quantified. It is found, for geophysically motivated parameter regimes, that the difference in bulk concentration subject to realizations of different source locations is highly correlated with the local flow topology of the source. Such flow topologies can be highlighted by Lagrangian coherent structures. Reaction is relatively enhanced in regions of strong stretching, and relatively suppressed in regions where vortices are present. In any case, the presence of a divergence-free background flow helps speed up the reaction process, especially when the flow is time-dependent. Probability density of various quantities characterizing the reaction processes is also obtained. This reveals the inherent complexity of the reaction-diffusion process subject to nonlinear background stirring.

  19. How Hydrate Saturation Anomalies are Diffusively Constructed and Advectively Smoothed

    NASA Astrophysics Data System (ADS)

    Rempel, A. W.; Irizarry, J. T.; VanderBeek, B. P.; Handwerger, A. L.

    2015-12-01

    The physical processes that control the bulk characteristics of hydrate reservoirs are captured reasonably well by long-established model formulations that are rooted in laboratory-verified phase equilibrium parameterizations and field-based estimates of in situ conditions. More detailed assessments of hydrate distribution, especially involving the occurrence of high-saturation hydrate anomalies have been more difficult to obtain. Spatial variations in sediment properties are of central importance for modifying the phase behavior and promoting focussed fluid flow. However, quantitative predictions of hydrate anomaly development cannot be made rigorously without also addressing the changes in phase behavior and mechanical balances that accompany changes in hydrate saturation level. We demonstrate how pore-scale geometrical controls on hydrate phase stability can be parameterized for incorporation in simulations of hydrate anomaly development along dipping coarse-grained layers embedded in a more fine-grained background that is less amenable to fluid transport. Model simulations demonstrate how hydrate anomaly growth along coarse-layer boundaries is promoted by diffusive gas transport from the adjacent fine-grained matrix, while advective transport favors more distributed growth within the coarse-grained material and so effectively limits the difference between saturation peaks and background levels. Further analysis demonstrates how sediment contacts are unloaded once hydrate saturation reaches sufficient levels to form a load-bearing skeleton that can evolve to produce segregated nodules and lenses. Decomposition of such growth forms poses a significant geohazard that is expected to be particularly sensitive to perturbations induced by gas extraction. The figure illustrates the predicted evolution of hydrate saturation Sh in a coarse-grained dipping layer showing how prominent bounding hydrate anomalies (spikes) supplied by diffusive gas transport at early times

  20. FOG-1-mediated recruitment of NuRD is required for cell lineage re-enforcement during haematopoiesis.

    PubMed

    Gao, Zhiguang; Huang, Zan; Olivey, Harold E; Gurbuxani, Sandeep; Crispino, John D; Svensson, Eric C

    2010-01-20

    The transcriptional co-factor Friend of GATA1 (FOG-1) has been shown to interact with subunits of the nucleosome remodelling and histone deacetylase (NuRD) complex through a specific motif located at its N-terminus. To test the importance of FOG-1/NuRD interaction for haematopoiesis in vivo, we generated mice with a mutation that specifically disrupts FOG-1/NuRD interaction (FOG-1(R3K5A)). Homozygous FOG-1(R3K5A) mice were found to have splenomegaly, extramedullary erythropoiesis, granulocytosis and thrombocytopaenia secondary to a block in megakaryocyte maturation. FOG-1(R3K5A/R3K5A) megakaryocytes and erythroid progenitors expressed increased levels of GATA2, showing that FOG-1/NuRD interaction is required for the earlier described 'GATA Switch'. In addition, ablation of FOG-1/NuRD interaction led to inappropriate expression of mast cell and eosinophil-specific genes in the megakaryocyte and erythroid lineages. Chromatin immunoprecipitation experiments revealed that the NuRD complex was not properly recruited to a mast cell gene promoter in FOG-1(R3K5A/R3K5A) megakaryocytes, suggesting that FOG-1/NuRD interaction is required for the direct suppression of mast cell gene expression. Taken together, these results underscore the importance of the FOG-1/NuRD interaction for the re-enforcement of lineage commitment during erythropoiesis and megakaryopoiesis in vivo.

  1. Smoothed particle hydrodynamics model for Landau-Lifshitz-Navier-Stokes and advection-diffusion equations.

    PubMed

    Kordilla, Jannes; Pan, Wenxiao; Tartakovsky, Alexandre

    2014-12-14

    We propose a novel smoothed particle hydrodynamics (SPH) discretization of the fully coupled Landau-Lifshitz-Navier-Stokes (LLNS) and stochastic advection-diffusion equations. The accuracy of the SPH solution of the LLNS equations is demonstrated by comparing the scaling of velocity variance and the self-diffusion coefficient with kinetic temperature and particle mass obtained from the SPH simulations and analytical solutions. The spatial covariance of pressure and velocity fluctuations is found to be in a good agreement with theoretical models. To validate the accuracy of the SPH method for coupled LLNS and advection-diffusion equations, we simulate the interface between two miscible fluids. We study formation of the so-called "giant fluctuations" of the front between light and heavy fluids with and without gravity, where the light fluid lies on the top of the heavy fluid. We find that the power spectra of the simulated concentration field are in good agreement with the experiments and analytical solutions. In the absence of gravity, the power spectra decay as the power -4 of the wavenumber-except for small wavenumbers that diverge from this power law behavior due to the effect of finite domain size. Gravity suppresses the fluctuations, resulting in much weaker dependence of the power spectra on the wavenumber. Finally, the model is used to study the effect of thermal fluctuation on the Rayleigh-Taylor instability, an unstable dynamics of the front between a heavy fluid overlaying a light fluid. The front dynamics is shown to agree well with the analytical solutions.

  2. Smoothed particle hydrodynamics model for Landau-Lifshitz-Navier-Stokes and advection-diffusion equations

    SciTech Connect

    Kordilla, Jannes; Pan, Wenxiao Tartakovsky, Alexandre

    2014-12-14

    We propose a novel smoothed particle hydrodynamics (SPH) discretization of the fully coupled Landau-Lifshitz-Navier-Stokes (LLNS) and stochastic advection-diffusion equations. The accuracy of the SPH solution of the LLNS equations is demonstrated by comparing the scaling of velocity variance and the self-diffusion coefficient with kinetic temperature and particle mass obtained from the SPH simulations and analytical solutions. The spatial covariance of pressure and velocity fluctuations is found to be in a good agreement with theoretical models. To validate the accuracy of the SPH method for coupled LLNS and advection-diffusion equations, we simulate the interface between two miscible fluids. We study formation of the so-called “giant fluctuations” of the front between light and heavy fluids with and without gravity, where the light fluid lies on the top of the heavy fluid. We find that the power spectra of the simulated concentration field are in good agreement with the experiments and analytical solutions. In the absence of gravity, the power spectra decay as the power −4 of the wavenumber—except for small wavenumbers that diverge from this power law behavior due to the effect of finite domain size. Gravity suppresses the fluctuations, resulting in much weaker dependence of the power spectra on the wavenumber. Finally, the model is used to study the effect of thermal fluctuation on the Rayleigh-Taylor instability, an unstable dynamics of the front between a heavy fluid overlaying a light fluid. The front dynamics is shown to agree well with the analytical solutions.

  3. Smoothed particle hydrodynamics model for Landau-Lifshitz Navier-Stokes and advection-diffusion equations

    SciTech Connect

    Kordilla, Jannes; Pan, Wenxiao; Tartakovsky, Alexandre M.

    2014-12-14

    We propose a novel Smoothed Particle Hydrodynamics (SPH) discretization of the fully-coupled Landau-Lifshitz-Navier-Stokes (LLNS) and advection-diffusion equations. The accuracy of the SPH solution of the LLNS equations is demonstrated by comparing the scaling of velocity variance and self-diffusion coefficient with kinetic temperature and particle mass obtained from the SPH simulations and analytical solutions. The spatial covariance of pressure and velocity fluctuations are found to be in a good agreement with theoretical models. To validate the accuracy of the SPH method for the coupled LLNS and advection-diffusion equations, we simulate the interface between two miscible fluids. We study the formation of the so-called giant fluctuations of the front between light and heavy fluids with and without gravity, where the light fluid lays on the top of the heavy fluid. We find that the power spectra of the simulated concentration field is in good agreement with the experiments and analytical solutions. In the absence of gravity the the power spectra decays as the power -4 of the wave number except for small wave numbers which diverge from this power law behavior due to the effect of finite domain size. Gravity suppresses the fluctuations resulting in the much weaker dependence of the power spectra on the wave number. Finally the model is used to study the effect of thermal fluctuation on the Rayleigh-Taylor instability, an unstable dynamics of the front between a heavy fluid overlying a light fluid. The front dynamics is shown to agree well with the analytical solutions.

  4. Mesoscale numerical simulation study of warm fog dissipation by salt particles seeding

    NASA Astrophysics Data System (ADS)

    He, Hui; Guo, Xueliang; Liu, Xiang'e.; Gao, Qian; Jia, Xingcan

    2016-05-01

    Based on the dynamic framework of WRF and Morrison 2-moment explicit cloud scheme, a salt-seeding scheme was developed and used to simulate the dissipation of a warm fog event during 6-7 November 2009 in the Beijing and Tianjin area. The seeding effect and its physical mechanism were studied. The results indicate that when seeding fog with salt particles sized 80 µm and at a quantity of 6 g m-2 at the fog top, the seeding effect near the ground surface layer is negative in the beginning period, and then a positive seeding effect begins to appear at 18 min, with the best effect appearing at 21 min after seeding operation. The positive effect can last about 35 min. The microphysical mechanism of the warm fog dissipation is because of the evaporation due to the water vapor condensation on the salt particles and coalescence with salt particles. The process of fog water coalescence with salt particles contributed mostly to this warm fog dissipation. Furthermore, two series of sensitivity experiments were performed to study the seeding effect under different seeding amounts and salt particles sizes. The results show that seeding fog with salt particles sized of 80 µm can have the best seeding effect, and the seeding effect is negative when the salt particle size is less than 10 µm. For salt particles sized 80 µm, the best seeding effect, with corresponding visibility of 380 m, can be achieved when the seeding amount is 30 g m-2.

  5. An object-oriented based daytime over land fog detection approach using EOS/MODIS data

    NASA Astrophysics Data System (ADS)

    Wen, Xiongfei; Liu, Liangming; Li, Wei; Dong, Pei

    2009-09-01

    A new algorithm is presented for land fog detection from daytime image of Earth Observation System Moderate Resolution Imaging Spectroradiometer (EOS/MODIS) data. Due to its outstanding spatial and spectral resolutions, this image is an ideal data source for fog detection. The algorithm utilizes an object-oriented technique to separate fog from other cloud types. In this paper, MOD35 product is first introduced to exclude cloud-free areas, and high clouds are removed with MODIS 26 band, and then a parameter named Normalized Difference Fog Index (NDFI) is proposed based on Streamer radiative model and MODIS data for fog detection. Through segmenting NDFI image into regions of pixels, and computing attributes (e.g. mean value of brightness temperature) for each region to create objects, each object could be identified based on the attributes selected to determine whether belongs to fog or cloud. Algorithm's performance is evaluated against ground-based measurements over China in winter. The algorithm is proved to be effective in detecting fog accurately based on two different test cases.

  6. Development testing of large volume water sprays for warm fog dispersal

    NASA Technical Reports Server (NTRS)

    Keller, V. W.; Anderson, B. J.; Burns, R. A.; Lala, G. G.; Meyer, M. B.; Beard, K. V.

    1986-01-01

    A new brute-force method of warm fog dispersal is described. The method uses large volume recycled water sprays to create curtains of falling drops through which the fog is processed by the ambient wind and spray induced air flow. Fog droplets are removed by coalescence/rainout. The efficiency of the technique depends upon the drop size spectra in the spray, the height to which the spray can be projected, the efficiency with which fog laden air is processed through the curtain of spray, and the rate at which new fog may be formed due to temperature differences between the air and spray water. Results of a field test program, implemented to develop the data base necessary to assess the proposed method, are presented. Analytical calculations based upon the field test results indicate that this proposed method of warm fog dispersal is feasible. Even more convincingly, the technique was successfully demonstrated in the one natural fog event which occurred during the test program. Energy requirements for this technique are an order of magnitude less than those to operate a thermokinetic system. An important side benefit is the considerable emergency fire extinguishing capability it provides along the runway.

  7. Fog interception by Sequoia sempervirens (D. Don) crowns decouples physiology from soil water deficit.

    PubMed

    Simonin, Kevin A; Santiago, Louis S; Dawson, Todd E

    2009-07-01

    Although crown wetting events can increase plant water status, leaf wetting is thought to negatively affect plant carbon balance by depressing photosynthesis and growth. We investigated the influence of crown fog interception on the water and carbon relations of juvenile and mature Sequoia sempervirens trees. Field observations of mature trees indicated that fog interception increased leaf water potential above that of leaves sheltered from fog. Furthermore, observed increases in leaf water potential exceeded the maximum water potential predicted if soil water was the only available water source. Because field observations were limited to two mature trees, we conducted a greenhouse experiment to investigate how fog interception influences plant water status and photosynthesis. Pre-dawn and midday branchlet water potential, leaf gas exchange and chlorophyll fluorescence were measured on S. sempervirens saplings exposed to increasing soil water deficit, with and without overnight canopy fog interception. Sapling fog interception increased leaf water potential and photosynthesis above the control and soil water deficit treatments despite similar dark-acclimated leaf chlorophyll fluorescence. The field observations and greenhouse experiment show that fog interception represents an overlooked flux into the soil-plant-atmosphere continuum that temporarily, but significantly, decouples leaf-level water and carbon relations from soil water availability.

  8. A Secure and Privacy-Preserving Navigation Scheme Using Spatial Crowdsourcing in Fog-Based VANETs.

    PubMed

    Wang, Lingling; Liu, Guozhu; Sun, Lijun

    2017-03-24

    Fog-based VANETs (Vehicular ad hoc networks) is a new paradigm of vehicular ad hoc networks with the advantages of both vehicular cloud and fog computing. Real-time navigation schemes based on fog-based VANETs can promote the scheme performance efficiently. In this paper, we propose a secure and privacy-preserving navigation scheme by using vehicular spatial crowdsourcing based on fog-based VANETs. Fog nodes are used to generate and release the crowdsourcing tasks, and cooperatively find the optimal route according to the real-time traffic information collected by vehicles in their coverage areas. Meanwhile, the vehicle performing the crowdsourcing task can get a reasonable reward. The querying vehicle can retrieve the navigation results from each fog node successively when entering its coverage area, and follow the optimal route to the next fog node until it reaches the desired destination. Our scheme fulfills the security and privacy requirements of authentication, confidentiality and conditional privacy preservation. Some cryptographic primitives, including the Elgamal encryption algorithm, AES, randomized anonymous credentials and group signatures, are adopted to achieve this goal. Finally, we analyze the security and the efficiency of the proposed scheme.

  9. Passive Fog Water Measurements Along the Northern California Coast During the Summer of 2014

    NASA Astrophysics Data System (ADS)

    Fernandez, D.; Torregrosa, A.; Weiss-Penzias, P. S.; Eljenholm, C. M.; Coffey, E. M.; Hernandez, C.; Mairs, A. A.

    2014-12-01

    As a part of the UC Santa Cruz, Moss Landing Marine Lab, and California State University Monterey Bay multi-year effort to track the cycling of methyl mercury compounds through fog deposition, researchers have deployed 1.00 m2 standard passive fog collectors based on the Schemenauer design at 13 locations throughout Northern California during the summer of 2014. These devices consist of a 1.00 m2 mesh that collects tiny fog water droplets that coalesce, fall into a trough and whose volume is recorded by a tipping bucket rain gauge at 15-minute intervals. These data provide an estimate of the fog density and a quantitative measurement of the amount of liquid water available from each fog event. Several of these sites were deployed in conjunction with active strand collectors based on Colorado State University's Caltech Active Strand Cloudwater Collector (CASCC) design which are used to collect clean water samples for the detection of mercury. This presentation will highlight the spatial and temporal variability observed within the data sets during this first summer (2014) of active collection. Of particular and significant note is the variability of the fog in relationship to distance from the coast as well as the latitudinal variability. We note that the observations coupled with accompanying meteorological measurements can potentially help to provide estimates of the potential flux of moisture available from fog events to ecosystem processes during the otherwise dry season along the California coast.

  10. Increase California-Oregon Coastal Summer Sea Level Fog from 1950 to 2007

    NASA Astrophysics Data System (ADS)

    Dorman, C. E.

    2015-12-01

    An analysis is presented of the marine fog distribution based upon the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) ship observations taken during 1950-2007. Deep fog occurrence is reported in routine weather reports that are encoded in an ICOADS ship observation. Occurrence is estimated by the number of deep fog observations divided by the total present weather observations in a one-degree area centered on latitude and longitude grid point intersections. The mean fog occurrence for the summer (June-July-August) 1950-2007 was computed for each one degree point. There is a long term, deep fog occurrence maximum on the California-Oregon coast with its highest value of 16.6 % at 38° N 123° W. This fog maximum is coincident with coldest June-July-August sea surface temperatures (SST) along the coast. To compute annual averages of the maximum, a block average was based on the 19 over water grid points with the deep fog occurrences generally greater than 0.6 times the highest long term maximum value that extended along the California-Oregon coast from 37° N to 44° N. The June-July-August block averaged, annual value computed for each of the 58 summers for the period 1950-2007 has a distinct positive trend. A line fitted to the data has a deep fog percent occurrence increase of +7.4 % from 1950 through 2007 or a trend of +0.13 % per year. The Mann-Kendall test was applied and the trend is significant at the 0.05 level. The increase in long term coastal fog is coincident with a decrease in the California-Oregon coastal SST. The SST decrease is consistent with interior California land temperatures increasing, increasing the cross shore sea level pressure gradient, and increasing the along coast winds creating a positive feedback that causes more upwelling and lower SST.

  11. Fog Inputs and Edge Effects From Canopy to Soil in a California Redwood Forest

    NASA Astrophysics Data System (ADS)

    Ewing, H. A.; Weathers, K. C.; Elliott, A.

    2005-12-01

    As a horizontally-driven vector, fog interacts with the structure of the landscape to create spatial patterns of deposition not seen in the more even distribution of vertically-delivered rainwater inputs. In coastal CA, fog arrives during the summer growing season when trees are most physiologically active and rainfall is negligible, thus it may be an ecologically significant source of water and nutrients. We are examining the interaction of horizontal and vertical inputs with forest structure, and the influence of these inputs on plant physiology, ecosystem fluxes, and soil characteristics in coastal redwood forests, Sonoma, CA. Fog water flux to the forest floor via throughfall (TF) was approximately 5 times greater at the windward (ocean-facing) edge than at sites on the interior of the patch, while rain delivery was more even across the whole forest patch. This edge effect for TF showed an exponential decline away from the windward forest edge; all sites greater than about 75 m from the edge received comparable fog inputs. Soil moisture patterns reflected the input pattern: the surface soil horizon at the windward edge had consistently greater water content than did interior sites throughout the fog season. After a large fog event, throughfall added to edge soils roughly doubled the moisture content at the soil surface. The absence of such input in the forest interior left relative water content lower by a factor of two to three compared to the edge site. While both tension and gravity lysimeters collected water at all sites in the forest during the rainy season, only tension lysimeters near the windward forest edge collected water in the fog season. These results suggest water availability at edge and interior locations can differ markedly during the fog water season and that fog may affect rates of primary production, biogeochemical cycling, and soil development.

  12. Summer water use by California coastal prairie grasses: fog, drought, and community composition.

    PubMed

    Corbin, Jeffrey D; Thomsen, Meredith A; Dawson, Todd E; D'Antonio, Carla M

    2005-10-01

    Plants in the Mediterranean climate region of California typically experience summer drought conditions, but correlations between zones of frequent coastal fog inundation and certain species' distributions suggest that water inputs from fog may influence species composition in coastal habitats. We sampled the stable H and O isotope ratios of water in non-photosynthetic plant tissue from a variety of perennial grass species and soil in four sites in northern California in order to determine the proportion of water deriving from winter rains and fog during the summer. The relationship between H and O stable isotopes from our sample sites fell to the right of the local meteoric water line (LMWL) during the summer drought, providing evidence that evaporation of water from the soil had taken place prior to the uptake of water by vegetation. We developed a novel method to infer the isotope values of water before it was subjected to evaporation in which we used experimental data to calculate the slope of the deltaH versus deltaO line versus the LMWL. After accounting for evaporation, we then used a two-source mixing model to evaluate plant usage of fog water. The model indicated that 28-66% of the water taken up by plants via roots during the summer drought came from fog rather than residual soil water from winter rain. Fog use decreased as distance from the coast increased, and there were significant differences among species in the use of fog. Rather than consistent differences in fog use by species whose distributions are limited to the coast versus those with broader distributions, species responded individualistically to summer fog. We conclude that fogwater inputs can mitigate the summer drought in coastal California for many species, likely giving an advantage to species that can use it over species that cannot.

  13. [Fog water absorption by the leaves of epiphytes and non - epiphytes in Xishuangbanna].

    PubMed

    Zheng, Yulong; Feng, Yulong

    2006-06-01

    Xishuangbanna is located at the northern margin of tropics. Its climate is different from that of typical tropics, but the rainforest there is not very different from that of the typical tropics in Southeast Asia. The main problems in Xishuangbanna are seasonal drought and low temperature. Fog may contribute to the development of rainforest here, but related studies are few. This study is aimed to know whether the leaves of epiphytes and non - epiphytes in Xishuangbanna can directly absorb fog water and contribute to their water status recovery, and whether epiphytes are more competent than non - epiphytes in their leaf fog water absorption. The study was conducted in dry season, and four species of epiphytes and six species of non - epiphytes were investigated. The effect of fog was imitated by spraying leaves with distilled water. For epiphytes and non - epiphytes, their leaf water potential (phi), relative water content (RWC), and amount of absorbed water increased gradually with the time of spraying, but the phi of epiphytes increased more quickly than that of non - epiphytes. The leaves of epiphytes Bolbitis scandens and Rhaphidophora decursiva could absorb fog water more quickly, and increase their RWC more greatly than those of non - epiphytes, indicating that these epiphytes were more competent than non - epiphytes in their leaf fog water absorption. The fog water absorption capacity of the leaves in epiphytic orchid Coelogyne occultata and Staurochilus dawsonianus was lower than that in Amischotolype hispida and Mananthus patentflora, but higher than that in other four non - epiphytes. The phi of epiphytes at early evening when no fog was formed was significantly lower than that at early morning, suggesting that fog water was absorbed by epiphytes at night to improve their leaf water status. Non - epiphytes did not need to absorb fog water directly through leaves, and they could recover their leaf water status through absorbing soil water by root system

  14. Clean fog rapid procedure test of artificially and naturally polluted HVDC porcelain barrel insulators

    SciTech Connect

    Vlastos, A.E. )

    1992-07-01

    The first question asked in this paper refers to the variation of the peak leakage current prior to the flashover and the variation of the time prior to flashover in the test of artificially polluted insulators when using the up-and-down method. To answer this question sums up the test procedure used in the up-and-down method. For each trial represented the insulator was again polluted artificially and then dried following the procedure described in the paper. Then the insulator was transported into the fog chamber and the voltage and fog was switched on simultaneously. In these experiments a low fog injection rate was used.

  15. The influence of summertime fog and overcast clouds on the growth of a coastal Californian pine: a tree-ring study.

    PubMed

    Williams, A Park; Still, Christopher J; Fischer, Douglas T; Leavitt, Steven W

    2008-06-01

    The coast of California is home to numerous rare, endemic conifers and other plants that are limited in distribution by drought sensitivity and the summer-dry climate that prevails across most of the state. Ecologists have long assumed that some coastal plant populations survived the early Pleistocene transition to a warmer and drier environment because they benefit from frequent fog and stratus clouds that provide water and shade during the rainless summer. One such population is that of Torrey pine (Pinus torreyana ssp. Insularis) on Santa Rosa Island in Channel Islands National Park. Here we report that the tree-ring width record from this population indicates strong growth sensitivities to summer fog drip and cloud shading. We quantified the effects of summer cloud cover by comparing ring-width indices to coastal airport cloud-frequency records (1944-2004). For the first time observed, summertime cloud frequency correlated positively with ring-width indices, regardless of whether the effect of rainfall was first removed from the ring-width record. The effect of ground-level fog was strongest in July early mornings (03:00 PST, R(2) = 0.262, P < 0.0002). The effect of clouds high enough to provide shade but not fog water was also strongest in July, but climbed steadily throughout the day before becoming strongest in late afternoon (16:00-18:00 PST, R(2) = 0.148, P < 0.004). Correlations were substantially stronger in years with higher soil moisture, suggesting that growth response to summer clouds is strongly affected by pre-summer rainfall. A change in the height and/or timing of coastal cloud formation with climate change would likely affect this and other populations of California's coastal vegetation.

  16. Anti-fogging nanofibrous SiO(2) and nanostructured SiO(2)-TiO(2) films made by rapid flame deposition and in situ annealing.

    PubMed

    Tricoli, Antonio; Righettoni, Marco; Pratsinis, Sotiris E

    2009-11-03

    Transparent, pure SiO(2), TiO(2), and mixed silica-titania films were (stochastically) deposited directly onto glass substrates by flame spray pyrolysis of organometallic solutions (hexamethyldisiloxane or tetraethyl orthosilicate and/or titanium tetra isopropoxide in xylene) and stabilized by in situ flame annealing. Silicon dioxide films consisted of a network of interwoven nanofibers or nanowires several hundred nm long and 10-15 nm thick, as determined by microscopy. These nanowire or nanofibrous films were formed by chemical vapor deposition (surface growth) on bare glass substrates during scalable combustion of precursor solutions at ambient conditions, for the first time to our knowledge, as determined by thermophoretic sampling of the flame aerosol and microscopy. In contrast, titanium dioxide films consisted of nanoparticles 3-5 nm in diameter that were formed in the flame and deposited onto the glass substrate, resulting in highly porous, lace-like nanostructures. Mixed SiO(2)-TiO(2) films (40 mol % SiO(2)) had similar morphology to pure TiO(2) films. Under normal solar radiation, all such films having a minimal thickness of about 300 nm completely prevented fogging of the glass substrates. These anti-fogging properties were attributed to inhibition of water droplet formation by such super-hydrophilic coatings as determined by wetting angle measurements. Deactivated (without UV radiation) pure TiO(2) coatings lost their super-hydrophilicity and anti-fogging properties even though their wetting angle was reduced by their nanowicking. In contrast, SiO(2)-TiO(2) coatings exhibited the best anti-fogging performance at all conditions taking advantage of the high surface coverage by TiO(2) nanoparticles and the super-hydrophilic properties of SiO(2) on their surface.

  17. Fog harvesting on the verge of economic competitiveness

    NASA Astrophysics Data System (ADS)

    Tiedemann, K. J.; Lummerich, A.

    2010-07-01

    Water scarcity is the bottleneck for agriculture and development of Peru’s coast and subject to aggravation due to climate change. Until present day, Peru’s coast in general and the Lima Metropolitan Area (LMA) in particular have enjoyed to a great extend the effect of the country’s high altitude glaciers that serve as a buffer for the capital’s water demand during the highland dry season. However, climate models predict the disappearance of this buffer system below 5.500 masl by 2015, leaving one of the driest places on earth with yet another decrease in freshwater supply (Zapata 2008). The deviation of water resources from the highlands has led already to allocation conflicts. Peru is in urgent need of new concepts for water management. Fog harvesting was introduced to South America in the 1980s and has since been implemented at various locations in North and Central America, Europe, Africa, Asia and Australia. The Standard Fog Collector (SFC) as described by Schemenauer and Cereceda (1994) has proven to be a successful instrument for this purpose. Apart from a number of small scale investigations, the design of the collector has barely been changed over the past three decades (e.g. Gioda et al. 1993). Within the framework of the presented project, financed primarily by the Global Exploration Fund of the National Geographic Society and Bayer AG, new fog collectors were designed at pilot and full scale. Best results in terms of simplicity of construction and water yield were obtained by a metal frame structure called Eiffel. While covering the same amount of space as an SFC and using the same Raschel 65% shadow net, the Eiffel collector harvested up to 2.650 liters of water within a frame of 8x4m compared to up to 600 liters of water harvested by a SFC at the same location. In combination with a simplified maintenance concept, our collectors present an economically competitive alternative to water supply by truck delivery in a region that is not likely to

  18. Analytical solution for the advection-dispersion transport equation in layered media

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The advection-dispersion transport equation with first-order decay was solved analytically for multi-layered media using the classic integral transform technique (CITT). The solution procedure used an associated non-self-adjoint advection-diffusion eigenvalue problem that had the same form and coef...

  19. Numerical Prediction of Cold Season Fog Events over Complex Terrain: the Performance of the WRF Model During MATERHORN-Fog and Early Evaluation

    NASA Astrophysics Data System (ADS)

    Pu, Zhaoxia; Chachere, Catherine N.; Hoch, Sebastian W.; Pardyjak, Eric; Gultepe, Ismail

    2016-09-01

    A field campaign to study cold season fog in complex terrain was conducted as a component of the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program from 07 January to 01 February 2015 in Salt Lake City and Heber City, Utah, United States. To support the field campaign, an advanced research version of the Weather Research and Forecasting (WRF) model was used to produce real-time forecasts and model evaluation. This paper summarizes the model performance and preliminary evaluation of the model against the observations. Results indicate that accurately forecasting fog is challenging for the WRF model, which produces large errors in the near-surface variables, such as relative humidity, temperature, and wind fields in the model forecasts. Specifically, compared with observations, the WRF model overpredicted fog events with extended duration in Salt Lake City because it produced higher moisture, lower wind speeds, and colder temperatures near the surface. In contrast, the WRF model missed all fog events in Heber City, as it reproduced lower moisture, higher wind speeds, and warmer temperatures against observations at the near-surface level. The inability of the model to produce proper levels of near-surface atmospheric conditions under fog conditions reflects uncertainties in model physical parameterizations, such as the surface layer, boundary layer, and microphysical schemes.

  20. Insights into association of the NuRD complex with FOG-1 from the crystal structure of an RbAp48·FOG-1 complex.

    PubMed

    Lejon, Sara; Thong, Sock Yue; Murthy, Andal; AlQarni, Saad; Murzina, Natalia V; Blobel, Gerd A; Laue, Ernest D; Mackay, Joel P

    2011-01-14

    Chromatin-modifying complexes such as the NuRD complex are recruited to particular genomic sites by gene-specific nuclear factors. Overall, however, little is known about the molecular basis for these interactions. Here, we present the 1.9 Å resolution crystal structure of the NuRD subunit RbAp48 bound to the 15 N-terminal amino acids of the GATA-1 cofactor FOG-1. The FOG-1 peptide contacts a negatively charged binding pocket on top of the RbAp48 β-propeller that is distinct from the binding surface used by RpAp48 to contact histone H4. We further show that RbAp48 interacts with the NuRD subunit MTA-1 via a surface that is distinct from its FOG-binding pocket, providing a first glimpse into the way in which NuRD assembly facilitates interactions with cofactors. Our RbAp48·FOG-1 structure provides insight into the molecular determinants of FOG-1-dependent association with the NuRD complex and into the links between transcription regulation and nucleosome remodeling.

  1. Insights into Association of the NuRD Complex with FOG-1 from the Crystal Structure of an RbAp48·FOG-1 Complex*

    PubMed Central

    Lejon, Sara; Thong, Sock Yue; Murthy, Andal; AlQarni, Saad; Murzina, Natalia V.; Blobel, Gerd A.; Laue, Ernest D.; Mackay, Joel P.

    2011-01-01

    Chromatin-modifying complexes such as the NuRD complex are recruited to particular genomic sites by gene-specific nuclear factors. Overall, however, little is known about the molecular basis for these interactions. Here, we present the 1.9 Å resolution crystal structure of the NuRD subunit RbAp48 bound to the 15 N-terminal amino acids of the GATA-1 cofactor FOG-1. The FOG-1 peptide contacts a negatively charged binding pocket on top of the RbAp48 β-propeller that is distinct from the binding surface used by RpAp48 to contact histone H4. We further show that RbAp48 interacts with the NuRD subunit MTA-1 via a surface that is distinct from its FOG-binding pocket, providing a first glimpse into the way in which NuRD assembly facilitates interactions with cofactors. Our RbAp48·FOG-1 structure provides insight into the molecular determinants of FOG-1-dependent association with the NuRD complex and into the links between transcription regulation and nucleosome remodeling. PMID:21047798

  2. Fog-harvesting potential of lubricant-impregnated electrospun nanomats.

    PubMed

    Lalia, Boor Singh; Anand, Sushant; Varanasi, Kripa K; Hashaikeh, Raed

    2013-10-22

    Hydrophobic PVDF-HFP nanowebs were fabricated by a facile electrospinning method and proposed for harvesting fog from the atmosphere. A strong adhesive force between the surface and a water droplet has been observed, which resists the water being shed from the surface. The water droplets on the inhomogeneous nanomats showed high contact angle hysteresis. The impregnation of nanomats with lubricants (total quartz oil and Krytox 1506) decreased the contact angle hysteresis and hence improved the roll off of water droplets on the nanomat surface. It was found that water droplets of 5 μL size (diameter = 2.1 mm) and larger roll down on an oil-impregnated surface, held vertically, compared to 38 μL (diameter = 4.2 mm) on a plain nanoweb. The contact angle hysteresis decreased from ~95 to ~23° with the Krytox 1506 impregnation.

  3. Disparities in glacial advection of Southern Ocean Intermediate Water to the South Pacific Gyre

    NASA Astrophysics Data System (ADS)

    Tapia, R.; Nürnberg, D.; Ronge, T.; Tiedemann, R.

    2015-01-01

    The Intermediate Waters formed in the Southern Ocean are critical for ventilating the thermocline in the Southern Hemisphere Gyres and transporting climatic signals from high to low latitudes on glacial-interglacial time-scales. Despite the importance of the Southern Ocean Intermediate Waters (SOIWs), information on past changes in SOIWs formation is fragmentary, and its impact on the South Pacific Gyre (SPG)'s thermocline largely unknown. Here, we present a 200 kyr record of paired Mg/Ca ratios and stable oxygen isotope from surface and deep dwelling planktonic foraminifera, from the SPG. On average, the Globigerina bulloides Mg/Ca-derived sea surface temperatures show similar conditions during the LGM and Marine Isotope Stage (MIS) 6 (9.4 °C versus 9.8 °C). In contrast, the subsurface temperatures derived from the Mg/Ca values of Globorotalia inflata and Globorotalia truncatulinoides suggest that LGM is ∼3 to ∼2 °C colder than MIS 6. Furthermore, at subsurface depths the reconstructed δ18Osw-ivc record (proxy for relative local salinity changes) suggests opposite glacial conditions, with slightly saltier-than-Holocene waters during MIS 6, and fresher-than-Holocene waters during LGM. Contrasting glacial scenarios, plausibly due to changes in the presence of SOIWs at the study site, suggest variable formation and/or advection of SOIWs to the SPG during different glacial stages. The variability in SOIWs is probably driven by the changes in the intensity of the Southern Westerly Winds.

  4. Modeling velocity in gradient flows with coupled-map lattices with advection.

    PubMed

    Lind, Pedro G; Corte-Real, João; Gallas, Jason A C

    2002-07-01

    We introduce a simple model to investigate large scale behavior of gradient flows based on a lattice of coupled maps which, in addition to the usual diffusive term, incorporates advection, as an asymmetry in the coupling between nearest neighbors. This diffusive-advective model predicts traveling patterns to have velocities obeying the same scaling as wind velocities in the atmosphere, regarding the advective parameter as a sort of geostrophic wind. In addition, the velocity and wavelength of traveling wave solutions are studied. In general, due to the presence of advection, two regimes are identified: for strong diffusion the velocity varies linearly with advection, while for weak diffusion a power law is found with a characteristic exponent proportional to the diffusion.

  5. The role and regulation of friend of GATA-1 (FOG-1) during blood development in the zebrafish.

    PubMed

    Amigo, Julio D; Ackermann, Gabriele E; Cope, John J; Yu, Ming; Cooney, Jeffrey D; Ma, Dongdong; Langer, Nathaniel B; Shafizadeh, Ebrahim; Shaw, George C; Horsely, Wyatt; Trede, Nikolaus S; Davidson, Alan J; Barut, Bruce A; Zhou, Yi; Wojiski, Sarah A; Traver, David; Moran, Tyler B; Kourkoulis, George; Hsu, Karl; Kanki, John P; Shah, Dhvanit I; Lin, Hui Feng; Handin, Robert I; Cantor, Alan B; Paw, Barry H

    2009-11-19

    The nuclear protein FOG-1 binds transcription factor GATA-1 to facilitate erythroid and megakaryocytic maturation. However, little is known about the function of FOG-1 during myeloid and lymphoid development or how FOG-1 expression is regulated in any tissue. We used in situ hybridization, gain- and loss-of-function studies in zebrafish to address these problems. Zebrafish FOG-1 is expressed in early hematopoietic cells, as well as heart, viscera, and paraspinal neurons, suggesting that it has multifaceted functions in organogenesis. We found that