Special Issue "Observation, Simulation and Predictability of Fog "

A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Meteorology".

Deadline for manuscript submissions: closed (30 April 2020).

Special Issue Editors

Dr. Thierry Bergot
E-Mail Website
Guest Editor
Centre National de Recherches Meteorologiques, CNRM-UMR 3589, Toulouse, France
Interests: stable boundary layer; fog and low cloud; mesoscale modeling; large-eddy simulations; predictability
Dr. Darko Koračin
E-Mail Website
Co-Guest Editor
University of Split, Split, Croatia
Interests: observations and modeling of marine fog; regional weather and climate modeling of coastal dynamics, cloudiness and air-sea interaction

Special Issue Information

Dear Colleagues,

The societal impact of fog has significantly increased during recent decades due to increasing air, marine and road traffic. The financial cost related to fog has become comparable to the losses from other weather events like storms.

Recent studies highlight the remaining difficulties in predicting and measuring fog at various scales of time and space. This Special Issue is expected to represent an important step in the direction of addressing new scientific challenges in fog-related research, and operational applications. Therefore, we invite authors to submit original articles that aim to study fog and its variability and predictability at various scales. Intercomparison studies of well-documented events are also welcomed.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers).

Dr. Thierry Bergot
Dr. Darko Koračin
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Atmosphere is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • numerical simulations of fog at various scales (from mesoscale to LES)
  • fog predictability and societal impact
  • fog observations at various scales (from mesoscale to local scale)
  • fog field experiment
  • fog processes study (radiation, dynamic and microphysic)
  • new methods of fog forecasting
  • marine, coastal and continental fog

Published Papers (18 papers)

Order results
Result details
Select all
Export citation of selected articles as:

Editorial

Jump to: Research

Editorial
Observation, Simulation and Predictability of Fog: Review and Perspectives
Atmosphere 2021, 12(2), 235; https://doi.org/10.3390/atmos12020235 - 09 Feb 2021
Viewed by 479
Abstract
Fog affects human activities in various ways, but the societal impact of fog has significantly increased during recent decades due to increasing air, marine and road traffic [...] Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )

Research

Jump to: Editorial

Article
Why Does Fog Deepen? An Analytical Perspective
Atmosphere 2020, 11(8), 865; https://doi.org/10.3390/atmos11080865 - 14 Aug 2020
Cited by 2 | Viewed by 932
Abstract
The overall depth of a fog layer is one of the important factors in determining the hazard that a fog event presents. With discrete observations and often coarse numerical grids, however, fog depth cannot always be accurately determined. To address this, we derive [...] Read more.
The overall depth of a fog layer is one of the important factors in determining the hazard that a fog event presents. With discrete observations and often coarse numerical grids, however, fog depth cannot always be accurately determined. To address this, we derive a simple analytical relation that describes the change in depth of a fog interface with time, which depends on the tendencies and vertical gradients of moisture. We also present a lengthscale estimate for the maximum depth over which mixing can occur in order for the fog layer to be sustained, assuming a uniform mixing of the vertical profiles of temperature and moisture. Even over several hours, and when coarse observational resolution is used, the analytical description is shown to accurately diagnose the depth of a fog layer when compared against observational data and the results of large-eddy simulations. Such an analytical description not only enables the estimation of sub-grid or inter-observation fog depth, but also provides a simple framework for interpreting the evolution of a fog layer in time. Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
Show Figures

Figure 1

Article
Fog Classification by Their Droplet Size Distributions: Application to the Characterization of Cerema’s Platform
Atmosphere 2020, 11(6), 596; https://doi.org/10.3390/atmos11060596 - 04 Jun 2020
Cited by 2 | Viewed by 892
Abstract
Fog is one of major challenges for transportation systems. The automation of the latter is based on perception sensors that can be disrupted by atmospheric conditions. As fog conditions are random and non-reproducible in nature, Cerema has designed a platform to generate fog [...] Read more.
Fog is one of major challenges for transportation systems. The automation of the latter is based on perception sensors that can be disrupted by atmospheric conditions. As fog conditions are random and non-reproducible in nature, Cerema has designed a platform to generate fog and rain on demand. Two types of artificial fog with different droplet size distributions are generated: they correspond to radiation fogs with small and medium droplets. This study presents an original method for classifying these different types of fog in a descriptive and quantitative way. It uses a new fog classification coefficient based on a principal component analysis, which measures the ability of a pair of droplet size distribution descriptors to differentiate between the two different types of fog. This method is applied to a database containing more than 12,000 droplet size distributions collected within the platform. It makes it possible to show: (1) that the two types of fog proposed by Cerema have significantly different droplet size distributions, for meteorological visibility values from 10 m to 1000 m; (2) that the proposed droplet size distribution range is included in the natural droplet size distribution range; (3) that the proposed droplet size distribution range should be extended in particular with larger droplets. Finally, the proposed method makes it possible to compare the different fog droplet size distribution descriptors proposed in the literature. Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
Show Figures

Figure 1

Article
Reconstructing Elemental Carbon Long-Term Trend in the Po Valley (Italy) from Fog Water Samples
Atmosphere 2020, 11(6), 580; https://doi.org/10.3390/atmos11060580 - 02 Jun 2020
Cited by 1 | Viewed by 785
Abstract
Elemental carbon (EC), a ubiquitous component of fine atmospheric aerosol derived from incomplete combustion, is an important player for both climate change and air quality deterioration. Several policy measures have been implemented over the last decades to reduce EC emissions from anthropogenic sources, [...] Read more.
Elemental carbon (EC), a ubiquitous component of fine atmospheric aerosol derived from incomplete combustion, is an important player for both climate change and air quality deterioration. Several policy measures have been implemented over the last decades to reduce EC emissions from anthropogenic sources, but still, long-term EC measurements to verify the efficacy of such measurements are limited. In this study, we analyze the concentration of EC suspended in fog water samples, collected over the period 1997–2016 in a rural background site of the southern Po Valley. The comparison between EC in fog water and EC atmospheric aerosol concentration measured since 2012 allowed us to reconstruct EC atmospheric concentration from fog water chemical composition dating back to 1997. The results agree with the EC atmospheric observations performed at the European Monitoring and Evaluation Program (EMEP) station of Ispra in the northern part of the Po Valley since 2002, and confirm that the Po Valley is a pollution hotspot, not only in urban areas, but also in rural locations. The reconstructed trend over the period 1997–2016 indicates that EC concentration during the winter season has decreased on average by 4% per year, in agreement with the emission reduction rate, confirming the effectiveness of air quality measures implemented during the past 20 years. Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
Show Figures

Figure 1

Article
Parameterization of Radiation Fog-Top Height and Methods Evaluation in Tianjin
Atmosphere 2020, 11(5), 480; https://doi.org/10.3390/atmos11050480 - 08 May 2020
Cited by 4 | Viewed by 585
Abstract
Different methods have been developed to estimate the fog-top height of radiation fog and evaluated using the measurements obtained from a 255-m meteorological tower located in Tianjin in 2016. Different indicators of turbulence intensity, friction velocity (u*), turbulence kinetic energy [...] Read more.
Different methods have been developed to estimate the fog-top height of radiation fog and evaluated using the measurements obtained from a 255-m meteorological tower located in Tianjin in 2016. Different indicators of turbulence intensity, friction velocity (u*), turbulence kinetic energy (TKE), and variance of vertical velocity (σw2) were used to estimate the fog-top height, respectively. Positive correlations between the fog-top height and u*, TKE, and σw2 were observed, with empirical parameterization schemes H = 583.35 × u * 1.12 , H = 205.4   ×   ( T K E ) 0.68 , and H = 420.10 × ( σ w 2 ) 0.51 being obtained. Among them, σw2 is the most appropriate indicators of turbulence intensity to estimate the fog-top height. Compared with sensible flux and condensation rate, the new form of convective velocity scale (w*) was the most appropriate indicator of buoyancy induced by radiative cooling, and the relationship H = 328.33 × w * 1.34 was obtained. σw2 and with w*, which represents the intensity of turbulence and buoyancy, were used to estimate the fog-top height. The relationship H = 396.26 ×   (σw + 0.1 ×   w*) − 16 was obtained, which can be used to accurately estimate the fog-top height. Moreover, the temperature convergence (TC) method was used to estimate the fog-top height; however, the results strongly rely on the threshold value. Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
Show Figures

Figure 1

Article
Towards a Better Representation of Fog Microphysics in Large-Eddy Simulations Based on an Embedded Lagrangian Cloud Model
Atmosphere 2020, 11(5), 466; https://doi.org/10.3390/atmos11050466 - 05 May 2020
Cited by 5 | Viewed by 780
Abstract
The development of radiation fog is influenced by multiple physical processes such as radiative cooling and heating, turbulent mixing, and microphysics, which interact on different spatial and temporal scales with one another. Once a fog layer has formed, the number of fog droplets [...] Read more.
The development of radiation fog is influenced by multiple physical processes such as radiative cooling and heating, turbulent mixing, and microphysics, which interact on different spatial and temporal scales with one another. Once a fog layer has formed, the number of fog droplets and their size distribution have a particularly large impact on the development of the fog layer due to their feedback on gravitational settling and radiative cooling at the fog top, which are key processes for fog. However, most models do not represent microphysical processes explicitly, or parameterize them rather crudely. In this study we simulate a deep radiation fog case with a coupled large-eddy simulation (LES)–Lagrangian cloud model (LCM) approach for the first time. By simulating several hundred million fog droplets as Lagrangian particles explicitly (using the so-called superdroplet approach), we include a size-resolved diffusional growth including Köhler theory and gravitational sedimentation representation. The results are compared against simulations using a state of the art bulk microphysics model (BCM). We simulate two different aerosol backgrounds (pristine and polluted) with each microphysics scheme. The simulations show that both schemes generally capture the key features of the deep fog event, but also that there are significant differences: the drop size distribution produced by the LCM is broader during the formation and dissipation phase than in the BCM. The LCM simulations suggest that its spectral shape, which is fixed in BCMs, exhibits distinct changes during the fog life cycle, which cannot be taken into account in BCMs. The picture of the overall fog droplet number concentration is twofold: For both aerosol environments, the LCM shows lower concentrations of larger fog droplets, while we observe a higher number of small droplets and swollen aerosols reducing the visibility earlier than in the BCM. As a result of the different model formulation we observe higher sedimentation rates and lower liquid water paths for the LCM. The present work demonstrates that it is possible to simulate fog with the computational demanding approach of LCMs to assess the advantages of high-resolution cloud models and further to estimate errors of traditional parameterizations. Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
Show Figures

Figure 1

Article
The Microphysical Properties of a Sea-Fog Event along the West Coast of the Yellow Sea in Spring
Atmosphere 2020, 11(4), 413; https://doi.org/10.3390/atmos11040413 - 20 Apr 2020
Cited by 1 | Viewed by 850
Abstract
The microphysics and visibility of a sea-fog event were measured at the Qingdao Meteorological Station (QDMS) (120°19′ E, 36°04′ N) from 5 April to 8 April 2017. The two foggy periods with low visibility (<200 m) lasted 31 h together. The mean value [...] Read more.
The microphysics and visibility of a sea-fog event were measured at the Qingdao Meteorological Station (QDMS) (120°19′ E, 36°04′ N) from 5 April to 8 April 2017. The two foggy periods with low visibility (<200 m) lasted 31 h together. The mean value of the average liquid water content (LWC) was 0.057 g m−3, and the mean value of the number concentration (NUM) was 64.4 cm−3. We found that although large droplets only constituted a small portion of the total number of the concentration; they contributed the majority of the LWC and therefore determined ~76% of total extinction of the visibility. The observed droplet-size distribution (DSD) exhibited a new bimodal Gaussian (G-exponential) distribution function, rather than the well-accepted Gamma distribution. This work suggests a new distribution function to describe fog DSD, which may help to improve the microphysical parameterization for the Yellow Sea fog numerical forecasting. Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
Show Figures

Figure 1

Article
Improvement of Fog Simulation by the Nudging of Meteorological Tower Data in the WRF and PAFOG Coupled Model
Atmosphere 2020, 11(3), 311; https://doi.org/10.3390/atmos11030311 - 23 Mar 2020
Cited by 4 | Viewed by 870
Abstract
Improvement of fog simulation accuracy was investigated for the fogs that occurred on the south coast of the Korean Peninsula using the WRF (3D) and PAFOG (1D) coupled model. In total, 22 fog cases were simulated and accuracy of the fog simulation was [...] Read more.
Improvement of fog simulation accuracy was investigated for the fogs that occurred on the south coast of the Korean Peninsula using the WRF (3D) and PAFOG (1D) coupled model. In total, 22 fog cases were simulated and accuracy of the fog simulation was examined based on Critical Success Index, Hit Rate and False Alarm Rate. The performance of the coupled WRF-PAFOG model was better than that of the single WRF model as expected. However, much more significant improvement appeared only when the data from a 300 m meteorological tower was not only used for the initial conditions but also nudged during the simulation. Moreover, a proper prescription of soil moisture was found to be important for accurate fog simulation especially for the fog cases with prior precipitation since efficient moisture supply from the precipitation-soaked soil might have been critical for fog formation. It was also demonstrated that with such optimal coupled model setting, a coastal radiation fog event with prior precipitation could be very realistically simulated: the fog onset and dissipation times matched so well with observation. In detail, radiative cooling at the surface was critical to form a surface inversion layer as the night fell. Then the vapor flux from the precipitation-soaked surface was confined within the inversion layer to form fog. It is suggested that a proper prescription of soil moisture in the model based on observations, if readily available, could be a cost-effective method for improving operational fog forecasting, considering the fact that tall meteorological towers are a rarity in the world. Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
Show Figures

Figure 1

Article
Fog Droplet Size Distribution and the Interaction between Fog Droplets and Fine Particles during Dense Fog in Tianjin, China
Atmosphere 2020, 11(3), 258; https://doi.org/10.3390/atmos11030258 - 05 Mar 2020
Cited by 4 | Viewed by 1101
Abstract
From November 2016 to January 2017, there were large-scale dense fog processes in Tianjin area on the west coast of Bohai Bay, China, even strong dense fog with visibility less than 50 m occurred. Based on the observation data of fog droplet spectrum [...] Read more.
From November 2016 to January 2017, there were large-scale dense fog processes in Tianjin area on the west coast of Bohai Bay, China, even strong dense fog with visibility less than 50 m occurred. Based on the observation data of fog droplet spectrum monitor, visibility sensor, environmental particle monitoring equipment and meteorological automatic station, the characteristics of fog droplet size distribution and the interaction between the fog droplets and fine particles during dense fog events were analyzed. The results show following characteristics: (1) The average concentration of fog droplets (Na), the average liquid water content (La) and the maximum liquid water content (Lmax) in the strong dense fog process are larger than those in the dense fog. The average spectrum of fog droplet size distribution conforms to Junge distribution, and they are all broad-spectrum fog with a spectrum width of about 45 μm. The average spectrum is similar to the dense fog of heavily industrialized inland in the world. (2) The maximum of fog droplet diameter during the formation stage have a good indication for the outbreak of strong dense fog. (3) The mass concentration of PM2.5 (CPM2.5) is ranged from 121–375 μg/m3, and the interaction between fog droplets and fine particles is analyzed. During the formation, development and maturity stages, fog process can scavenge atmospheric fine particles, and the scavenging efficiency of PM2.5 is more remarkable than PM10. When CPM2.5 does not exceed 350 μg/m3, the increase in the concentration of fine particles is conducive to the rapid growth of fog droplets and the sharp drop of visibility. However, when CPM2.5 exceeds the critical value, the increase has a negative feedback effect on the development of the fog process. More investigations and cases are necessary to fully assess the mechanisms related to the dense fog events in Tianjin area and further analysis will be done. Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
Show Figures

Figure 1

Article
The Use of Thermal Infra-Red Imagery to Elucidate the Dynamics and Processes Occurring in Fog
Atmosphere 2020, 11(3), 240; https://doi.org/10.3390/atmos11030240 - 29 Feb 2020
Cited by 3 | Viewed by 813
Abstract
Improving our ability to predict fog accurately is currently a high priority for Numerical Weather Prediction models. Such an endeavour requires numerous types of observations of real fog as a means to both better understand it and also provide an assessment of model [...] Read more.
Improving our ability to predict fog accurately is currently a high priority for Numerical Weather Prediction models. Such an endeavour requires numerous types of observations of real fog as a means to both better understand it and also provide an assessment of model performance. We consider the use of thermal infra-red imagery, used in conjunction with other meteorological observations, for the purposes of studying fog. Two cameras were used—a FLIR Systems Inc. A655sc and a FLIR Systems Inc. A65sc—which were set up to capture one image per minute. Images were then combined to provide video footage of nocturnal fog events. Results show that the imagery from such cameras can provide great insight into fog processes and dynamics, identifying interesting features not previously seen. Furthermore, comparison of imagery with conventional meteorological observations showed that the observations were often not capable of being used to delineate all of the processes affecting fog, due to their incomplete and local nature. Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
Show Figures

Figure 1

Article
Influence of Quasi-Periodic Oscillation of Atmospheric Variables on Radiation Fog over A Mountainous Region of Korea
Atmosphere 2020, 11(3), 230; https://doi.org/10.3390/atmos11030230 - 27 Feb 2020
Cited by 2 | Viewed by 781
Abstract
To enhance our understanding of fog processes over complex terrain, various fog events that occurred during the International Collaborative Experiments for Pyeongchang 2018 Winter Olympics and Paralympics (ICE-POP) campaign were selected. Investigation of thermodynamic, dynamic, and microphysical conditions within fog layers affected by [...] Read more.
To enhance our understanding of fog processes over complex terrain, various fog events that occurred during the International Collaborative Experiments for Pyeongchang 2018 Winter Olympics and Paralympics (ICE-POP) campaign were selected. Investigation of thermodynamic, dynamic, and microphysical conditions within fog layers affected by quasi-periodic oscillation of atmospheric variables was conducted using observations from a Fog Monitor-120 (FM-120) and other in-situ meteorological instruments. A total of nine radiation fog cases that occurred in the autumn and winter seasons during the campaign over the mountainous region of Pyeongchang, Korea were selected. The wavelet analysis was used to study quasi-period oscillations of dynamic, microphysical, and thermodynamic variables. By decomposing the time series into the time-frequency space, we can determine both dominant periods and how these dominant periods change in time. Quasi-period oscillations of liquid water content (LWC), pressure, temperature, and horizontal/vertical velocity, which have periods of 15–40 min, were observed during the fog formation stages. We hypothesize that these quasi-periodic oscillations were induced by Kelvin–Helmholtz instability. The results suggest that Kelvin–Helmholtz instability events near the surface can be explained by an increase in the vertical shear of horizontal wind and by a simultaneous increase in wind speed when fog forms. In the mature stages, fluctuations of the variables did not appear near the surface anymore. Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
Show Figures

Figure 1

Article
Investigations on the Influence of Chemical Compounds on Fog Microphysical Parameters
Atmosphere 2020, 11(3), 225; https://doi.org/10.3390/atmos11030225 - 26 Feb 2020
Cited by 2 | Viewed by 739
Abstract
Lab experiments related to artificial fog studies are limited due to instrument sensitivity to small fog and aerosol particles; therefore, the goal of this work is to evaluate aerosol solute effects on fog physical properties in a lab environment. To reach the goal, [...] Read more.
Lab experiments related to artificial fog studies are limited due to instrument sensitivity to small fog and aerosol particles; therefore, the goal of this work is to evaluate aerosol solute effects on fog physical properties in a lab environment. To reach the goal, an automated fog-generating system was designed and that includes controlled chemical compounds dissolved in pure water. In the analysis, the impact of changing the mass concentration of potassium dihydrogen phosphate—KH2PO4, urea-CO(NH2)2, and potassium hexacyanoferrate trihydrate-K3(Fe(CN)6) on fog droplet size spectra is studied, because visibility is directly related to fog droplet spectra and aerosol composition. In the experiment, various microphysical conditions, including fog droplet size and volume concentration, were analyzed as a function of changing aerosol composition/spectra and fixed thermodynamic conditions. The results showed that fog droplet size spectra vary with the addition of chemical impurities to the pure water volume. For example, increasing KH2PO4 concentration compared to distilled water volume resulted in a higher mean particle size, which led to faster droplet settlement, and that resulted in cleaning air more efficiently compared to pure water fog. Overall, both issues and challenges of the experimental fog generating system with respect to water and aerosol solutions resembling CRBN (chemical, radiological, biological, and nuclear agents) characteristics are provided and evaluated. Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
Show Figures

Graphical abstract

Article
Changes in Fog, Ice Fog, and Low Visibility in the Hudson Bay Region: Impacts on Aviation
Atmosphere 2020, 11(2), 186; https://doi.org/10.3390/atmos11020186 - 10 Feb 2020
Cited by 4 | Viewed by 899
Abstract
Fog and low visibility present a natural hazard for aviation in the Hudson Bay region. Sixteen communities on the eastern and western shores of Hudson and James Bays, Canada, were selected for fog, ice fog, and low visibility statistical analyses for a range [...] Read more.
Fog and low visibility present a natural hazard for aviation in the Hudson Bay region. Sixteen communities on the eastern and western shores of Hudson and James Bays, Canada, were selected for fog, ice fog, and low visibility statistical analyses for a range of 21 to 62 year time series. Both fog hours and ice fog hours were found to be in general decline, with some locations experiencing statistically significant declines. Spatial asymmetries for fog and ice fog were observed among the various areas within the Hudson Bay region. The more northerly locations in this study experienced statistically significant declines in fog hours while the southerly locations’ declines were not significant. Fog was significantly declining in some western Hudson Bay locations during spring and fall and in James Bay during winter and summer, but minimal trends were observed in eastern Hudson Bay. For ice fog hours, all of the locations in the western shore of Hudson Bay experienced a significant decline in winter while only one-third of the locations in eastern shores were found to be declining significantly during winter. Blowing snow, snow, ice and fog were the leading causes for reduced and low visibilities at the majority of the locations. Other factors such as rain contributed a minor role to low visibility. Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
Show Figures

Figure 1

Article
Influence of Arctic Oscillation on Frequency of Wintertime Fog Days in Eastern China
Atmosphere 2020, 11(2), 162; https://doi.org/10.3390/atmos11020162 - 04 Feb 2020
Cited by 4 | Viewed by 768
Abstract
The influence of Arctic Oscillation (AO) on the frequency of wintertime fog days in eastern China is studied based on the winter AO index, the wintertime fog-day data of national stations in China, and the National Centers for Environmental Prediction/National Center for Atmospheric [...] Read more.
The influence of Arctic Oscillation (AO) on the frequency of wintertime fog days in eastern China is studied based on the winter AO index, the wintertime fog-day data of national stations in China, and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data from 1954 to 2007. The results show that heavy fog and light fog are more likely to occur during winter in eastern China with the strong interannual variability. During the winter with the positive-phase AO, there are more days of heavy fog in North China but less in South China, while light fog days become more in the whole of eastern China. It is mainly because that when AO is in the positive phase, the pressure in the polar region decreases at 500 hPa; the pressure in East Asia increases anomalously; the East Asian trough decreases; and the low-level westerly jet moves northward, preventing the northwesterly cold air from moving southward. Therefore, the whole eastern China gets warmer and wetter air, and there are more light fog days with the enhanced water vapor. However, the atmosphere merely becomes more towards unstable in South China, where the precipitation increases but the heavy fog days decreases. Nevertheless, heavy fog days increase with the water vapor in North China because of moving towards a stable atmosphere, which is formed by the anomalous downdrafts north of the precipitation center in South China. When AO is in the negative phase, the situation is basically opposite to that in the positive phase, but the variations of the corresponding fog days and circulations are weaker than those in the AO-positive-phase winter, which may be related to the nonlinear effect of AO on climate. Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
Show Figures

Figure 1

Article
Direct Numerical Simulation of Fog: The Sensitivity of a Dissipation Phase to Environmental Conditions
Atmosphere 2020, 11(1), 12; https://doi.org/10.3390/atmos11010012 - 21 Dec 2019
Cited by 2 | Viewed by 812
Abstract
The sensitivity of fog dissipation to the environmental changes in radiation, liquid-water lapse rate, free tropospheric temperature and relative humidity was studied through numerical experiments designed based on the 2007-Paris Fog observations. In particular, we examine how much of the stratocumulus-thinning mechanism can [...] Read more.
The sensitivity of fog dissipation to the environmental changes in radiation, liquid-water lapse rate, free tropospheric temperature and relative humidity was studied through numerical experiments designed based on the 2007-Paris Fog observations. In particular, we examine how much of the stratocumulus-thinning mechanism can be extended to the near-surface clouds or fog. When the free troposphere is warmed relative to the reference case, fog-top descends and become denser. Reducing the longwave radiative cooling via a more emissive free troposphere favors thickening the physical depth of fog, unlike cloud-thinning in a stratocumulus cloud. Drying the free troposphere allows fog thinning and promotes fog dissipation while sustaining the entrainment rate. The numerical simulation results suggest that the contribution of entrainment drying is more effective than the contribution of entrainment warming yielding the reduction in liquid water path tendency and promoting the onset of fog depletion relative to the reference case studied here. These sensitivity experiments indicate that the fog lifting mechanism can enhance the effect of the inward mixing at the fog top. However, to promote fog dissipation, an inward mixing mechanism only cannot facilitate removing humidity in the fog layer unless a sufficient entrainment rate is simultaneously sustained. Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
Show Figures

Figure 1

Article
A Preliminary Impact Study of Wind on Assimilation and Forecast Systems into the One-Dimensional Fog Forecasting Model COBEL-ISBA over Morocco
Atmosphere 2019, 10(10), 615; https://doi.org/10.3390/atmos10100615 - 11 Oct 2019
Cited by 5 | Viewed by 949
Abstract
The assimilation impact of wind data from aircraft measurements (AMDAR), surface synoptic observations (SYNOP) and 3D numerical weather prediction (NWP) mesoscale model, on short-range numerical weather forecasting (up to 12 h) and on the assimilation system, using the one-dimensional fog forecasting model COBEL-ISBA [...] Read more.
The assimilation impact of wind data from aircraft measurements (AMDAR), surface synoptic observations (SYNOP) and 3D numerical weather prediction (NWP) mesoscale model, on short-range numerical weather forecasting (up to 12 h) and on the assimilation system, using the one-dimensional fog forecasting model COBEL-ISBA (Code de Brouillard à l’Échelle Locale-Interactions Soil Biosphere Atmosphere), is studied in the present work. The wind data are extracted at Nouasseur airport, Casablanca, Morocco, over a winter period from the national meteorological database. It is the first time that wind profiles (up to 1300 m) are assimilated in the framework of a single-column model. The impact is assessed by performing NWP experiments with data denial tests, configured to be close to the operational settings. The assimilation system estimates the flow-dependent background covariances for each run of the model and takes the cross-correlations between temperature, humidity and wind components into account. When assimilated into COBEL-ISBA with an hourly update cycle, the wind field has a positive impact on temperature and specific humidity analysis and forecasts accuracy. Thus, a superior fit of the analysis background fields to observations is found when assimilating AMDAR without NWP wind data. The latter has shown a detrimental impact in all experiments. Besides, wind assimilation gave a clear improvement to short-range forecasts of near-surface thermodynamical parameters. Although, assimilation of SYNOP and AMDAR wind measurements slightly improves the probability of detection of fog but also increases the false alarms ratio by a lower magnitude. Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
Show Figures

Figure 1

Article
Loss to Aviation Economy Due to Winter Fog in New Delhi during the Winter of 2011–2016
Atmosphere 2019, 10(4), 198; https://doi.org/10.3390/atmos10040198 - 12 Apr 2019
Cited by 10 | Viewed by 1923
Abstract
Stable and clear atmospheric conditions, lower surface temperatures, an ample moisture supply, and a strong low-level inversion persisting for most of the night usually facilitates the formation of dense fog during winter in Delhi. This severely hinders the flight operations at India’s busiest [...] Read more.
Stable and clear atmospheric conditions, lower surface temperatures, an ample moisture supply, and a strong low-level inversion persisting for most of the night usually facilitates the formation of dense fog during winter in Delhi. This severely hinders the flight operations at India’s busiest airport, the Indira Gandhi International (IGI) Airport, where more than 900 flight operations occur per day and an interruption can cause significant financial losses to the aviation industry. It is important to undertake a quantitative study of the estimated losses. This study, undertaken for the first time in India, aimed to evaluate the impact of dense fog at IGI Airport on economic losses which occurred during the winter season between 2011 and 2016. The breakdown of charges for different segments of flight operations for the domestic and international sectors was obtained from India’s Ministry of Civil Aviation and the Center for Asia Pacific Aviation (CAPA) India. A total of 653 h of dense fog between 2011 and 2016 at IGI Airport caused economic losses of approximately 3.9 million USD (248 million Indian rupees) to the airlines. The analysis further found that from 2014–2015 onwards, there has been a reduction in the number of flight delays, diversions, and cancellations by approximately 88%, 55%, and 36%, respectively, due to the strict implementation of guidelines to facilitate the Category (CAT)-III landing for aircraft during dense fog. Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
Show Figures

Figure 1

Article
On the Predictability of Radiation Fog Formation in a Mesoscale Model: A Case Study in Heterogeneous Terrain
Atmosphere 2019, 10(4), 165; https://doi.org/10.3390/atmos10040165 - 28 Mar 2019
Cited by 5 | Viewed by 1235
Abstract
This study evaluates the predictability of the formation phase of a radiation fog event observed during the night of 31 October 2015 to 01 November 2015 in the north-east of France at three sites managed by OPE (Observatoire Pérenne de l’Environnement). The fog [...] Read more.
This study evaluates the predictability of the formation phase of a radiation fog event observed during the night of 31 October 2015 to 01 November 2015 in the north-east of France at three sites managed by OPE (Observatoire Pérenne de l’Environnement). The fog layer shows significantly different behaviors at the three areas, which are located only a few kilometers apart. Three fog life cycles were observed: the formation of a dense adiabatic fog, the formation of a thin patchy fog, or no fog formation despite favorable conditions. This event was studied with the Meso-NH numerical mesoscale model at two horizontal resolutions, 500 m and 50 m. Simulations at 50 m allow estimation of the spread of the predicted parameters over the heterogeneous terrain studied. These numerical simulations strongly suggest that this event involved numerous interactions and complex circulations. The wind above the nocturnal boundary layer greatly affects the transition of shallow patchy fog into thick adiabatic fog. These numerical simulations also show that the occurrence and type of fog could be very different over a small but heterogeneous area. It is also interesting to note that the spread of the simulated parameters was very high during the transition from shallow fog to a deep fog layer. The spread was concentrated during the regime transition between the fog formation and its maturity. This appeared to be the result of the complex interplay of processes at numerous ranges of scale. A new concept called “pseudo-process diagram” is presented. These pseudo-process diagrams are very good tools to analyze fog, and allow a good illustration of the spread of fog during this chaotic phase. This kind of concept seems a promising tool to analyze fog predictability in depth. Full article
(This article belongs to the Special Issue Observation, Simulation and Predictability of Fog )
Show Figures

Figure 1

Back to TopTop