A review on ice fog measurements and modeling

Gültepe, Ismail; Zhou, Binbin; Milbrandt, Jason A.; Bott, Andreas; Li, Ying; Heymsfield, Andrew J.; Ferrier, Brad S.; Ware, Randolph; Pavolonis, Michael J.; Kühn, Thomas; Gurka, James J.; Liu, P.; Čermák, Jan

doi:10.1016/j.atmosres.2014.04.014

Cited by 80 publications

(67 citation statements)

References 87 publications

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“…The temperature, RH, vapour density and liquid water content (LWC) profiles in this study are retrieved from PMWR measurements at zenith direction. The temporal resolution is 2-3 min, and the vertical resolutions are 50 m from the surface to 500 m, 100 m from 500 to 2000 m and 250 m from 2000 to 10 000 m. The accuracy of PMWR profiles is compatible with most meteorology applications, especially in the lower troposphere (Cimini et al, 2011;Ware et al, 2013;Gultepe et al, 2015).…”

Section: Observational Site and Instrumentsmentioning

confidence: 76%

Quantifying the relationship between PM<sub>2.5</sub> concentration, visibility and planetary boundary layer height for long-lasting haze and fog–haze mixed events in Beijing

et al. 2018

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Abstract. Air quality and visibility are strongly influenced by aerosol loading, which is driven by meteorological conditions. The quantification of their relationships is critical to understanding the physical and chemical processes and forecasting of the polluted events. We investigated and quantified the relationship between PM 2.5 (particulate matter with aerodynamic diameter is 2.5 µm and less) mass concentration, visibility and planetary boundary layer (PBL) height in this study based on the data obtained from four long-lasting haze events and seven fog-haze mixed events from January 2014 to March 2015 in Beijing. The statistical results show that there was a negative exponential function between the visibility and the PM 2.5 mass concentration for both haze and fog-haze mixed events (with the same R 2 of 0.80). However, the fog-haze events caused a more obvious decrease of visibility than that for haze events due to the formation of fog droplets that could induce higher light extinction. The PM 2.5 concentration had an inversely linear correlation with PBL height for haze events and a negative exponential correlation for fog-haze mixed events, indicating that the PM 2.5 concentration is more sensitive to PBL height in fog-haze mixed events. The visibility had positively linear correlation with the PBL height with an R 2 of 0.35 in haze events and positive exponential correlation with an R 2 of 0.56 in foghaze mixed events. We also investigated the physical mechanism responsible for these relationships between visibility, PM 2.5 concentration and PBL height through typical haze and fog-haze mixed event and found that a double inversion layer formed in both typical events and played critical roles in maintaining and enhancing the long-lasting polluted events. The variations of the double inversion layers were closely associated with the processes of long-wave radiation cooling in the nighttime and short-wave solar radiation reduction in the daytime. The upper-level stable inversion layer was formed by the persistent warm and humid southwestern airflow, while the low-level inversion layer was initially produced by the surface long-wave radiation cooling in the nighttime and maintained by the reduction of surface solar radiation in the daytime. The obvious descending process of the upper-level inversion layer induced by the radiation process could be responsible for the enhancement of the lowlevel inversion layer and the lowering PBL height, as well as high aerosol loading for these polluted events. The reduction of surface solar radiation in the daytime could be around 35 % for the haze event and 94 % for the fog-haze mixed event. Therefore, the formation and subsequent descending processes of the upper-level inversion layer should be an important factor in maintaining and strengthening the longlasting severe polluted events, which has not been revealed in previous publications. The interactions and feedbacks between PM 2.5 concentration and PBL height linked by radiation process caused a more significant an...

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Section: Observational Site and Instrumentsmentioning

confidence: 76%

Quantifying the relationship between PM<sub>2.5</sub> concentration, visibility and planetary boundary layer height for long-lasting haze and fog–haze mixed events in Beijing

et al. 2018

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“…Thus it is a significant sample of midlatitude winter conditions. The same methodology should in principle be applicable to other climate zones as well, although ice crystals in fog occurring in very cold conditions would require a different retrieval method for fog optical properties due to the larger particle sizes (Gultepe et al, 2015). For pure liquid fog, the methodology should be generalisable to all fog types, as the radiative processes are not directly dependent on the fog formation mechanism.…”

Section: Discussionmentioning

confidence: 99%

Radiation in fog: quantification of the impact on fog liquid water based on ground-based remote sensing

Wærsted¹,

Haeffelin

Dupont

et al. 2017

Atmos. Chem. Phys.

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Abstract. Radiative cooling and heating impact the liquid water balance of fog and therefore play an important role in determining their persistence or dissipation. We demonstrate that a quantitative analysis of the radiation-driven condensation and evaporation is possible in real time using groundbased remote sensing observations (cloud radar, ceilometer, microwave radiometer). Seven continental fog events in midlatitude winter are studied, and the radiative processes are further explored through sensitivity studies. The longwave (LW) radiative cooling of the fog is able to produce 40-70 g m −2 h −1 of liquid water by condensation when the fog liquid water path exceeds 30 g m −2 and there are no clouds above the fog, which corresponds to renewing the fog water in 0.5-2 h. The variability is related to fog temperature and atmospheric humidity, with warmer fog below a drier atmosphere producing more liquid water. The appearance of a cloud layer above the fog strongly reduces the LW cooling relative to a situation with no cloud above; the effect is strongest for a low cloud, when the reduction can reach 100 %. Consequently, the appearance of clouds above will perturb the liquid water balance in the fog and may therefore induce fog dissipation. Shortwave (SW) radiative heating by absorption by fog droplets is smaller than the LW cooling, but it can contribute significantly, inducing 10-15 g m −2 h −1 of evaporation in thick fog at (winter) midday. The absorption of SW radiation by unactivated aerosols inside the fog is likely less than 30 % of the SW absorption by the water droplets, in most cases. However, the aerosols may contribute more significantly if the air mass contains a high concentration of absorbing aerosols. The absorbed radiation at the surface can reach 40-120 W m −2 during the daytime depending on the fog thickness. As in situ measurements indicate that 20-40 % of this energy is transferred to the fog as sensible heat, this surface absorption can contribute significantly to heating and evaporation of the fog, up to 30 g m −2 h −1 for thin fog, even without correcting for the typical underestimation of turbulent heat fluxes by the eddy covariance method. Since the radiative processes depend mainly on the profiles of temperature, humidity and clouds, the results of this paper are not site specific and can be generalised to fog under different dynamic conditions and formation mechanisms, and the methodology should be applicable to warmer and moister climates as well. The retrieval of approximate emissivity of clouds above fog from cloud radar should be further developed.

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“…Considering this case and others observed during the year examined here, there appears to be a correlation between sub-freezing surface temperatures and poor performance in the FLS algorithm. The temperatures likely aren't cold enough for this to be 'ice fog' [Gultepe et al, 2015], which the algorithm is not designed to detect [Calvert and Pavolonis, 2010]. It may not be the sub-zero surface temperatures per se that create the poor detections.…”

Section: Canberra: 12-15 June 2016mentioning

confidence: 99%

Validation of a Satellite-based Fog and Low Stratus Detection Algorithm Using Himawari-8 over Australia

Lucas¹

2017

Bureau Research Report

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A review on ice fog measurements and modeling

Cited by 80 publications

References 87 publications

Quantifying the relationship between PM<sub>2.5</sub> concentration, visibility and planetary boundary layer height for long-lasting haze and fog–haze mixed events in Beijing

Quantifying the relationship between PM<sub>2.5</sub> concentration, visibility and planetary boundary layer height for long-lasting haze and fog–haze mixed events in Beijing

Radiation in fog: quantification of the impact on fog liquid water based on ground-based remote sensing

Validation of a Satellite-based Fog and Low Stratus Detection Algorithm Using Himawari-8 over Australia

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A review on ice fog measurements and modeling

Cited by 80 publications

References 87 publications

Quantifying the relationship between PM&lt;sub&gt;2.5&lt;/sub&gt; concentration, visibility and planetary boundary layer height for long-lasting haze and fog–haze mixed events in Beijing

Quantifying the relationship between PM&lt;sub&gt;2.5&lt;/sub&gt; concentration, visibility and planetary boundary layer height for long-lasting haze and fog–haze mixed events in Beijing

Radiation in fog: quantification of the impact on fog liquid water based on ground-based remote sensing

Validation of a Satellite-based Fog and Low Stratus Detection Algorithm Using Himawari-8 over Australia

Contact Info

Product

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Quantifying the relationship between PM<sub>2.5</sub> concentration, visibility and planetary boundary layer height for long-lasting haze and fog–haze mixed events in Beijing

Quantifying the relationship between PM<sub>2.5</sub> concentration, visibility and planetary boundary layer height for long-lasting haze and fog–haze mixed events in Beijing