A field study of radiation fog in meppen, West Germany

Choularton, T. W.; Fullarton, G.; Latham, John; Mill, C. S.; Smith, M. H.; Stromberg, I. M.

doi:10.1002/qj.49710745209

Cited by 35 publications

(12 citation statements)

References 9 publications

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“…Meyer et al (1986) discuss a field project located at Albany, New York. Fuzzi et al (1992) present an overview of the Po Valley fog experiment in Italy, Choularton et al (1981) present a fog case in Germany, and Duynkerke (1991) presents observations of fog made in the Netherlands. To a greater or lesser degree all of these projects presented observations of stability within fog layers, and a discussion of the physics involved.…”

Section: Introductionmentioning

confidence: 99%

Radiation Fog. Part I: Observations of Stability and Drop Size Distributions

Price

2011

Boundary-Layer Meteorol

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Data from several cases of radiation fog occurring at the Met Office field site at Cardington, Bedfordshire, UK have been analyzed with a view to elucidating the typical evolution in its static stability from formation to dissipation. Typically the early stages of radiation fog are characterized by a stable thermal profile and a relatively shallow depth. However, when the fog reached approximately 100 m depth it was observed to become optically thick (to longwave radiation), with a subsequent change over several hours to a saturated adiabatic stability profile. At this time turbulence levels were seen to increase significantly. The mechanisms involved appear to be radiative cooling from fog top and a positive heat flux to the atmosphere from the soil. The importance of this change in stability for numerical modelling of fog episodes is discussed. Several case studies are made to gain some insight into how common this transition is. Droplet spectra were measured at 2-m height for many of the cases considered, and their evolution is discussed. It is found that distributions fall into an initial phase with small drop sizes (approximately ≤10 µm diameter) and concentration, and a mature phase with the appearance of much larger drop sizes with a mean diameter of approximately 15−20 µm. It is found that the appearance of the mature phase does not coincide with the change in stability from stable to saturated adiabatic, but there is some evidence that once a saturated adiabatic profile is established, the droplet spectra variations are significantly less than for the stable period. The observed evolution of these spectra brings into question the suitability of microphysical schemes that assume constant spectral shape, drop diameter, and number density.

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Section: Introductionmentioning

confidence: 99%

Radiation Fog. Part I: Observations of Stability and Drop Size Distributions

Price

2011

Boundary-Layer Meteorol

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“…A microphysical definition for fog has been studied (Tampieri and Tomasi, 1976;Pinnick et al, 1978;Chourlaton et al, 1981;Steward and Essenwanger, 1982;Minnis et al, 1992;Roach, 1994;Wetzel et al, 1996;Miles et al, 2000;Brenguier et al, 2000;Bendix, 2002). Then, Cermak and Bendix (2008) defined that the cloud optical thickness (COT) ranges from 0.5 to 30, and the effective radius (Re) varies between 3 and 12 µm with a maximum of 20 µm in coastal fog.…”

Section: Methodsmentioning

confidence: 97%

Fog detection using geostationary satellite data: Temporally continuous algorithm

Lee

Chung

2011

Asia-Pacific J Atmos Sci

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A fog detection algorithm that uses geostationary satellite data has been developed and tested. This algorithm focuses on continuous fog detection since temporal discontinuities, especially at dawn and dusk, are a major problem with current fog detection algorithms that use satellite imagery data. This is because the spectral radiance at 3.7 µm contains overlapping emissive and reflectance components. In order to determine the radiance at 3.7 µm under fog conditions, radiative transfer model simulations were performed. The results showed that the radiance at 3.7 µm obviously varies with the solar zenith angle, and the brightness temperature differences between 3.7 µm and 10.8 µm are completely dissimilar between day and night (positive and varying with the angle during the daytime, but negative and constant at night). In this algorithm, a dynamic threshold is used as a function of the solar zenith angle. Moreover, additional criteria such as infrared, split-window channels, and a water vapor channel are used to remove high-level clouds. Also, the visible reflectance (0.67 µm) channel is used in the daytime algorithm because visible channel images are very practical for confirming a fog area with the high reflectivity and the smooth texture. The clear-sky visible reflectance for the previous 15 days was also employed to eliminate the surface effect that appeared during dawn and dusk. As the results, fog areas were estimated continuously, allowing the lifecycle of the fog system, from its development to decline, to appear obviously in the resulting images. Moreover, the estimated fog areas matched well with surface observations, except in a high latitude region that was covered by thin cirrus clouds.

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“…SPENCER et al (1976) found that the major effect on the droplet growth process was due to increased competition for vapor due to the nucleation of new droplets. However, CHOULARTON et al (1981) argued that large supersaturation fluctuations or convective motions near the fog top produced large drops in radiation fog. GERBER (1991) had a similar opinion about supersaturation.…”

Section: Burst Reinforcement and Droplet Spectrum Broadeningmentioning

confidence: 99%

“…Supersaturated environment (BARONTI and ELZWEIG, 1973), radiative cooling (ROACH, 1976a, b), and turbulent mixing (GERBER, 1981) were suggested to be the principal agents of droplet growth. However, the study of CHOULARTON et al (1981) indicated that larger drops cannot be produced by radiative cooling but by large supersaturation fluctuations or by convective motions. SPENCER et al (1976) suggested that the major effect upon the droplet growth process is from the increasing competition for vapor due to the nucleation of new droplets.…”

Section: Introductionmentioning

confidence: 99%

Summary of a 4-Year Fog Field Study in Northern Nanjing, Part 2: Fog Microphysics

Niu

Liu

Zhao

et al. 2011

Pure Appl. Geophys.

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Comprehensive field observations of fog were conducted during the winters of 2006-2009 at the Nanjing University of Information Science & Technology, in order to study macro-and micro-physical structures and physical-chemical processes of dense fogs in northern Nanjing. The fog boundary-layer structures of different types and their corresponding characteristics are presented in Part I of these twin papers. In this second part, microphysical characteristics and droplet spectrum distributions of different types of fogs, microphysical relationships (among fog droplet concentration, liquid water content, and mean diameter), and microphysics of atmospheric aerosols during haze/fog events are discussed. The results show that there are large differences in microphysical parameters among four types of haze/fog. Many interesting phenomena, including fog burst reinforcement, fog droplet spectrum broadening, fog bimodal or multi-modal drop-size distributions, and critical triggering maxD value of fog coagulation growth, were captured during the 4-year field study.

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A field study of radiation fog in meppen, West Germany

Cited by 35 publications

References 9 publications

Radiation Fog. Part I: Observations of Stability and Drop Size Distributions

Radiation Fog. Part I: Observations of Stability and Drop Size Distributions

Fog detection using geostationary satellite data: Temporally continuous algorithm

Summary of a 4-Year Fog Field Study in Northern Nanjing, Part 2: Fog Microphysics

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