Deep Fog Research Articles

Identifying key stages of radiation fog evolution using water vapor isotopes

Fog is tied to surface energy and water budgets. However, our knowledge about the processes leading to fog evolution is still fragmentary, and their adequate representation in numerical-weather-prediction and climate models remains challenging. Water vapor isotopes are widely used to investigate Earth's water cycle dynamics and can provide process-based insights into fog evolution. Although isotopes of water vapor and droplets during radiation fog have been reported, the intra-event isotope dynamics and the mechanisms controlling water vapor isotope variability during radiation fog evolution have hardly been investigated. We use water vapor isotopes (δ2Hv, dv) combined with meteorological and eddy-covariance measurements, plus vertical profiles from a high-resolution numerical-weather-prediction model (COSMO-1), to study the processes that influence radiation fog evolution. Variability in surface-humidity and water vapor isotopes is tied to the different stages (shallow, transitional, and deep fog) of radiation fog evolution and affected by condensation, turbulent entrainment, fog droplet deposition at the surface, and evaporation processes. Strong water vapor isotopic fluctuations during radiation fog are linked to fog lifting to stratus-clouds during nighttime that lead to fog dissipation at ground level. Our results reveal highly correlated atmospheric-specific-humidity (qa) and water vapor isotopes during dew formation which is typical before the onset of radiation fog and in combination with fog; whilst during fog periods, δ2Hv and dv show larger temporal variability than qa due to their sensitivity to fog dynamics. Particularly, during fog growth, entrainment of air from the fog-top caused increasing dv, which was otherwise constant during condensation. Furthermore, δ2Hv variability during the transition into deep fog likely indicated the alternation of condensation-induced-decrease and entrainment-induced-increase of δ2Hv. Compared to the temporal isotope variability (with a magnitude of 34.6‰ for δ2Hv) associated with large-scale cold-frontal-clouds, radiation fog evolution is found to be associated with isotope variability of a similar amplitude (24.6‰ for δ2Hv).

Crime of Men, Punishment of Nature and Voice of the Irish: A Study on W. B. Yeats’ ‘The Curse of the Fires and of the Shadows’

Ecocriticism analyzes literary texts from environmental perspective to show the changes and impacts of nature upon people and their lives. William Butler Yeats uses elements of nature and blends history with legend in ‘The Curse of the Fires and of the Shadows’ where history says, Hamilton burnt Sligo Abbey in 1642 and legend says, a troop of Hamilton got lost in the deep fog and a man on a white horse misled them, which caused their doom. Yeats’ story contains a plot marking a revenge taken by nature. According to some scholars, natives of colonies are a part of nature. Killing native monks and consequently disturbing nature, Hamilton’s troops committed a crime. Yeats ensures punishment of the criminal for this crime and hence he personifies elements of nature such as fires, shadows, horse and the moon. This paper interprets Yeats’ ‘The Curse of the Fires and of the Shadows’ in the light of ecocriticism in order to find out how natural elements contribute to promote Irishness and raise the voice of colonized Ireland against the colonizer. This research also aims to identify the ecocritical consciousness of Yeats and to discuss what means he receives to punish humans for their crime against nature. In short, this paper explores Yeats’ rigorous use of nature and illustrates the crime of men, nature’s punishment for that crime and the voice of the Irish portrayed with connotative shadows.

Towards a Better Representation of Fog Microphysics in Large-Eddy Simulations Based on an Embedded Lagrangian Cloud Model

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.

Off-axis spatiotemporally gated multimode detection toward deep fog imaging.

Towards better imaging through fog for vehicles, we developed an off-axis spatiotemporally gated multimode laser scanning imaging system. Utilizing fog mimicking liquid suspension, we tested the imaging system with different levels of scattering. The experimental results suggest that the system can yield high quality images at seven scattering path lengths, which far exceeds the capability of conventional imaging systems. We also found that the multimode detection can not only make the system robust in the presence of aberration but also help to reduce the speckles in images for the case of coherent illumination.

Large-eddy simulation of radiation fog with comprehensive two-moment bulk microphysics: impact of different aerosol activation and condensation parameterizations

Abstract. In this paper we study the influence of the cloud microphysical parameterization, namely the effect of different methods for calculating the supersaturation and aerosol activation, on the structure and life cycle of radiation fog in large-eddy simulations. For this purpose we investigate a well-documented deep fog case as observed at Cabauw (the Netherlands) using high-resolution large-eddy simulations with a comprehensive bulk cloud microphysics scheme. By comparing saturation adjustment with a diagnostic and a prognostic method for calculating supersaturation (while neglecting the activation process), we find that, even though assumptions for saturation adjustment are violated, the expected overestimation of the liquid water mixing ratio is negligible. By additionally considering activation, however, our results indicate that saturation adjustment, due to approximating the underlying supersaturation, leads to a higher droplet concentration and hence significantly higher liquid water content in the fog layer, while diagnostic and prognostic methods yield comparable results. Furthermore, the effect of different droplet number concentrations is investigated, induced by using different common activation schemes. We find, in line with previous studies, a positive feedback between the droplet number concentration (as a consequence of the applied activation schemes) and strength of the fog layer (defined by its vertical extent and amount of liquid water). Furthermore, we perform an explicit analysis of the budgets of condensation, evaporation, sedimentation and advection in order to assess the height-dependent contribution of the individual processes on the development phases.

On the Predictability of Radiation Fog Formation in a Mesoscale Model: A Case Study in Heterogeneous Terrain

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.

Atmospheric Boundary Layer Structure and Turbulence during Sea Fog on the Southern China Coast

Abstract Small-scale turbulence has an essential role in sea-fog formation and evolution, but is not completely understood. This study analyzes measurements of the small-scale turbulence, together with the boundary layer structure and the synoptic and mesoscale conditions over the life cycle of a cold advection fog event and a warm advection fog event, both off the coast of southern China. The measurement data come from two sites: one on the coast and one at sea. These findings include the following: 1) For cold advection fog, the top can extend above the inversion base, but formation of an overlaying cloud causes the fog to dissipate. 2) For warm advection fog, two layers of low cloud can merge to form deep fog, with the depth exceeding 1000 m, when strong advection of warm moist air produces active thermal-turbulence mixing above the thermal-turbulence interface. 3) Turbulence near the sea surface is mainly thermally driven for cold advection fog, but mechanically driven for warm advection fog. 4) The momentum fluxes of both fog cases are below 0.04 kg m−1 s−2. However, the sensible and latent heat flux differ between the cases: in the cold advection fog case, the sensible and latent heat fluxes are roughly upward, averaging 2.58 and 26.75 W m−2, respectively; however, in the warm advection fog case, the sensible and latent heat flux are mostly downward, averaging −6.98 and −6.22 W m−2, respectively. 5) Low-level vertical advection is important for both fogs, but has a larger influence on fog development in the warm advection fog case.

Summary of a 4-Year Fog Field Study in Northern Nanjing, Part 1: Fog Boundary Layer

Comprehensive fog field observations were conducted during the winters of 2006–2009 at the Nanjing University of Information Science and Technology to study the macro and micro-physical structures and the physical–chemical processes of dense fogs in the area. The observations included features of the fog boundary layer, characteristics of fog water, the particle spectrum, the chemical composition of atmospheric aerosols, radiation and heat components, turbulence, meteorological elements (air temperature, pressure, wind speed, wind direction), and environmental monitoring. The fogs observed were divided into four types: radiation fog, advection–radiation fog, advection fog, and precipitation fog, according to the mechanisms and primary factors of the fog processes. Fog boundary-layer structures of different types and their corresponding characteristics were then studied. Fog boundary-layer features, temperature structures, wind fields, and fog maintenance are discussed. The results show that radiation fog had remarkable diurnal variation and formed mostly at sunset or midnight, and lifted after sunrise or at noon, and that advection–radiation fog and advection fog were of very long duration. Extremely dense fogs occurred only in radiation-related cases. Inversion in radiation fog was short-lived, disappearing 1 or 2 hours after sunrise or at noon, faster than that in advection–radiation fog. When wind direction reversed from easterly to westerly or from southerly to northerly, the fog became an extremely dense fog. Low-level jet at times impeded fog development, whereas at other times it encouraged fog continuance. The deep inversion was merely an essential condition for a thick fog layer; sufficient vapor supply was advantageous to the formation and maintenance of a deep fog layer.

In this issue: Proteomics 6/2008

AbstractIn this issue of Proteomics you will find the following highlighted articles:Reversing dimensions for quantitation: chromatography and electrophoresisFrom somewhere in the deep fog of the past, remnants of my sophomore physics surface occasionally. This time it is part of a physics lecture on symmetry and the statement that even the dimension of time was reversible. Tribl et al. scrambled the order of chromatographic and electrophoretic separations and used both stable isotopic and fluorescent labels. They started by tagging proteins with DIGE system CyDyes (Cy3, Cy5) for sensitive fluorescent labeling and tagging with isotope coded 12C‐ or 13C‐N‐nicotinoyloxy‐succinimide for relative quantitation. The doubly‐labeled proteins were fractionated on strong anion exchange (ten fractions) followed by reverse phase chromatography (nine fractions) to reduce peptide complexity. They further separated proteins by 1‐D SDS‐PAGE. Differentially labeled proteins were excised, digested and analyzed by nano‐RPC‐ESI‐MS/MS for identification by mass fingerprint. The authors feel the new protocol is complementary to 2‐D DIGE.Tribl, F. et al., Proteomics 2008, 8, 1204–1211.Tangles and tangled tangles: tauopathies, synucleinopathies and proteasomesGetting rid of the garbage in a cell is not a trivial matter: damaged or unneeded proteins are flagged with ubiquitin and transported to a proteasome, a complex structure of gates and rings where proteins are sorted out, chopped up and dumped out for further processing. Malfunctions of this system (tau‐types or synuclein‐type) can be serious – they are implicated in a number of progressive neurological syndromes, including Alzheimer's, Pick's disease, progressive supranuclear palsy (all taus), and Parkinson's (synuclein). To examine the proteasome proteins involved, Zouambia et al. tested antibodies raised against most of the subunits and subcomplexes as well as a set of overlapping peptides from protein MS73c. The antibodies were used in ELISA, molecular immunohistological and Western blot detection. The results were complicated and depended on whether the antigen target was native or denatured and tau‐ or synuclein‐defect dependent. Clearly, the proteasome proteome will be a very complex affair.Zouambia, M. et al., Proteomics 2008, 8, 1221–1236.How much interest does a brain bank pay?It depends… How fresh is it? Did it have any interesting diseases? What was its IQ? Any special talents? Did it visit any labs, oops, farms in Transylvania? It would be convenient to have a pop‐up indicator that signals a brain is overcooked, but we don't, so Crecelius et al. used a proteomic approach to find appropriate markers of grey matter status. The critical factors are the postmortem interval (PMI, time between death and storage at –80°C) and storage temperature prior to freezing. Samples stored under various conditions of time (2–48 h) and temperature (4°C and RT) were analyzed by 2‐D DIGE (pH 4–7) and MALDI‐TOF/TOF for protein mass fingerprint identification. Interestingly, out of ∼2000 spots, only ∼6% showed a significant change in quantity at RT, and only 2.5% showed changes at 4°C after 48 h. Changes included both increases and decreases.Crecelius, A. et al., Proteomics 2008, 8, 1276–1291.

Cover Picture: Proteomics 6/2008

AbstractIn this issue of Proteomics you will find the following highlighted articles:Reversing dimensions for quantitation: chromatography and electrophoresisFrom somewhere in the deep fog of the past, remnants of my sophomore physics surface occasionally. This time it is part of a physics lecture on symmetry and the statement that even the dimension of time was reversible. Tribl et al. scrambled the order of chromatographic and electrophoretic separations and used both stable isotopic and fluorescent labels. They started by tagging proteins with DIGE system CyDyes (Cy3, Cy5) for sensitive fluorescent labeling and tagging with isotope coded 12C‐ or 13C‐N‐nicotinoyloxy‐succinimide for relative quantitation. The doubly‐labeled proteins were fractionated on strong anion exchange (ten fractions) followed by reverse phase chromatography (nine fractions) to reduce peptide complexity. They further separated proteins by 1‐D SDS‐PAGE. Differentially labeled proteins were excised, digested and analyzed by nano‐RPC‐ESI‐MS/MS for identification by mass fingerprint. The authors feel the new protocol is complementary to 2‐D DIGE.Tribl, F. et al., Proteomics 2008, 8, 1204–1211.Tangles and tangled tangles: tauopathies, synucleinopathies and proteasomesGetting rid of the garbage in a cell is not a trivial matter: damaged or unneeded proteins are flagged with ubiquitin and transported to a proteasome, a complex structure of gates and rings where proteins are sorted out, chopped up and dumped out for further processing. Malfunctions of this system (tau‐types or synuclein‐type) can be serious – they are implicated in a number of progressive neurological syndromes, including Alzheimer's, Pick's disease, progressive supranuclear palsy (all taus), and Parkinson's (synuclein). To examine the proteasome proteins involved, Zouambia et al. tested antibodies raised against most of the subunits and subcomplexes as well as a set of overlapping peptides from protein MS73c. The antibodies were used in ELISA, molecular immunohistological and Western blot detection. The results were complicated and depended on whether the antigen target was native or denatured and tau‐ or synuclein‐defect dependent. Clearly, the proteasome proteome will be a very complex affair.Zouambia, M. et al., Proteomics 2008, 8, 1221–1236.How much interest does a brain bank pay?It depends… How fresh is it? Did it have any interesting diseases? What was its IQ? Any special talents? Did it visit any labs, oops, farms in Transylvania? It would be convenient to have a pop‐up indicator that signals a brain is overcooked, but we don't, so Crecelius et al. used a proteomic approach to find appropriate markers of grey matter status. The critical factors are the postmortem interval (PMI, time between death and storage at –80°C) and storage temperature prior to freezing. Samples stored under various conditions of time (2–48 h) and temperature (4°C and RT) were analyzed by 2‐D DIGE (pH 4–7) and MALDI‐TOF/TOF for protein mass fingerprint identification. Interestingly, out of ∼2000 spots, only ∼6% showed a significant change in quantity at RT, and only 2.5% showed changes at 4°C after 48 h. Changes included both increases and decreases.Crecelius, A. et al., Proteomics 2008, 8, 1276–1291.

Surface-to-Atmosphere Exchange in a River Valley Environment

AbstractObservations of the turbulent exchange between a river surface and the atmosphere in a mountainous area in southern Brazil are presented and discussed. A micrometeorological tower was installed directly above the surface of a 60-m-wide river. This paper describes the observed turbulent fluxes over 12 days of observations at this site. Eddy correlation sensible and latent heat fluxes are directed toward the river during daytime and from the river at night, and they are controlled by differences between water and air temperatures. The magnitude of the vertical fluxes between the river and the atmosphere increases during daytime with increasing temperature gradient up to a threshold, beyond which the increasing stability starts to dampen the fluxes. Water and air temperatures show very little variations across the width of the river, indicating that the measurements taken at one margin may be representative of the mean river exchange. Local scalar budgets show that daytime warming and moistening rates above the river are controlled by local transport from the riverbanks. The main vertical fluxes have a very small magnitude: 0.8 W m−2 for sensible heat and 1.1 W m−2 for latent heat. Events of very large sensible heat fluxes from the river to the atmosphere and very large latent heat fluxes from the atmosphere to the river happened on 3 days, following nights with a very deep fog layer in the valley. These events represented the passage of a warm and dry air mass down the river. A process to explain the occurrence of these large fluxes is suggested that is associated with differential fog dissipation over the valley.

Classification of cloud types based on data of multiple satellite sensors

Taking advantage of multispectral radiometers of VTIR of MOS-1 consisting of water vapor absorption and split-window channels, an attempt is made to develop an algorithm to classify cloud types of synopic meteorological significance. Verification of the algorithm based on the data of 4 channels of VTIR ( 1 visible, 1 water vapor absorption, 2 split window channels) onboard MOS-1 indicate that the algorithm works well for identifying well developed cumulonimbus, multilayered thick clouds and stratus/dense deep fog.

Observations of the structure of a deep fog : Brown, R., 1987. Met. Mag., Lond., 116(1384):329–338

Observations of the structure of a deep fog : Brown, R., 1987. Met. Mag., Lond., 116(1384):329–338

The Life Cycle of Valley Fog. Part II: Fog Microphysics

Extensive measurements were made of the microphysics of valley fog in the Chemung River Valley near Elmira, New York. This paper discusses data on drop size distributions, drop concentrations, liquid water contents, and haze and cloud nucleus concentrations obtained on eight fog nights. The behavior patterns of the microphysical variables were found to be extremely consistent. Shallow ground fog usually occurs prior to the formation of deep valley fog. The data show that ground fog is characterized by droplet concentrations of 100 to 200 per cubic centimeter in the 1 to 10 μm radius range with mean radii of 2 to 4 μm. As deep fog forms aloft, droplet concentration near the surface decreases to less than 2 cm−3 and the mean radius increases from 6 to 12 μm. Droplets of radii <3 μm disappear. Thereafter, droplet concentration and liquid water content increase gradually until the first visibility minimum at the surface when typical values range from 12 to 25 cm−3 and 50 to 150 mg cm−3, respectively. The small droplets reappear at first visibility minimum. Subsequently, bimodal drop size distributions occur in approximately half of the fogs with one mode at 2–3 μm radius and a second mode between 6 and 12 μm. Aloft, drop size distributions become narrower and the mean radius decreases with both increasing altitude and increasing age of the fog. The cloud nucleus concentration active at S = 3.0% is usually between 800 and 1000 cm−3 near the surface and decreases to 500–800 cm−3 at 300 m. It is argued from the data that supersaturation in the thin ground fog exceeds that in deep fog. The initial surface obscuration in deep fog appears to be due to droplets that form aloft and are transported downward into unsaturated air by turbulent diffusion. New droplets are apparently not generated near the surface until after the first visibility minimum.

Visibility variations at Schiphol-Airport, Amsterdam

Transmissometer records at Schiphol-Airport, Amsterdam have been analyzed to show the frequencies of visibility changes, in periods between 1 and 16 minutes, on occasions that the visibility is below 1000 metres for at least 30 minutes. Tables are presented for the frequencies of visibility changes in shallow and in deep fog, both for increasing and decreasing visibilities, with an initial visibility in the range of 60–1000 metres (the lower limit of this range is connected with the length of the transmissometer-baseline in use).

Observations of the vertical structure of a stratus cloud and radiation fogs in relation to the mechanism of drizzle formation

Observations of the vertical structure of radiation fogs and a stratus cloud were made by means of a rotary droplet sampler and other techniques. The results of the surveys of four radiation fogs and one stratus cloud are presented. It is found that the upper part of a deep fog or a stratus cloud has a similar physical structure to a cumulus cloud. The observation reveals that ordinary fog droplets grow mainly by condensation. It is also found that the presence of large droplets of radii about 50 microns or more near the top of the fog or stratus cloud is a necessary condition for the production of drizzle. The rate of growth of the large droplets is approximately explained by the Langmuir's accretion theory. DOI: 10.1111/j.2153-3490.1962.tb01342.x

Observations of the vertical structure of a stratus cloud and radiation fogs in relation to the mechanism of drizzle formation

Observations of the vertical structure of radiation fogs and a stratus cloud were made by means of a rotary droplet sampler and other techniques. The results of the surveys of four radiation fogs and one stratus cloud are presented. It is found that the upper part of a deep fog or a stratus cloud has a similar physical structure to a cumulus cloud. The observation reveals that ordinary fog droplets grow mainly by condensation. It is also found that the presence of large droplets of radii about 60 microns or more near the top of the fog or stratus cloud is a necessary condition for the production of drizzle. The rate of growth of the large droplets is approximately explained by the Langmuir’s accretion theory.