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    Ground-Based Observations and Modeling of the Visibility and Radar Reflectivity in a Radiation Fog Layer

    Source: Journal of Atmospheric and Oceanic Technology:;2012:;volume( 030 ):;issue: 002::page 288
    Author:
    Boers, R.
    ,
    Baltink, H. Klein
    ,
    Hemink, H. J.
    ,
    Bosveld, F. C.
    ,
    Moerman, M.
    DOI: 10.1175/JTECH-D-12-00081.1
    Publisher: American Meteorological Society
    Abstract: he development of a radiation fog layer at the Cabauw Experimental Site for Atmospheric Research (51.97°N, 4.93°E) on 23 March 2011 was observed with ground-based in situ and remote sensing observations to investigate the relationship between visibility and radar reflectivity. The fog layer thickness was less than 200 m. Radar reflectivity values did not exceed ?25 dBZ even with visibilities less than 100 m. The onset and evaporation of fog produce different radar reflectivity?visibility relationships. The evolution of the fog layer was modeled with a droplet activation model that used the aerosol size distribution observed at the 60-m altitude tower level as input. Radar reflectivity and visibility were calculated from model drop size spectra using Mie scattering theory. Since radiative cooling rates are small in comparison with cooling rates due to adiabatic lift of aerosol-laden air, the modeled supersaturation remains low so that few aerosol particles are activated to cloud droplets. The modeling results suggest that the different radar reflectivity?visibility relationships are the result of differences in the interplay between water vapor and cloud droplets during formation and evaporation of the fog. During droplet activation, only a few large cloud droplets remain after successfully competing for water vapor with the smaller activated droplets. These small droplets eventually evaporate (deactivate) again. In the fog dissolution/evaporation stage, only these large droplet need to be evaporated. Therefore, to convert radar reflectivity to visibility for traffic safety products, knowledge of the state of local fog evolution is necessary.
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      Ground-Based Observations and Modeling of the Visibility and Radar Reflectivity in a Radiation Fog Layer

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    http://yetl.yabesh.ir/yetl1/handle/yetl/4228097
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    • Journal of Atmospheric and Oceanic Technology

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    contributor authorBoers, R.
    contributor authorBaltink, H. Klein
    contributor authorHemink, H. J.
    contributor authorBosveld, F. C.
    contributor authorMoerman, M.
    date accessioned2017-06-09T17:24:37Z
    date available2017-06-09T17:24:37Z
    date copyright2013/02/01
    date issued2012
    identifier issn0739-0572
    identifier otherams-84729.pdf
    identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4228097
    description abstracthe development of a radiation fog layer at the Cabauw Experimental Site for Atmospheric Research (51.97°N, 4.93°E) on 23 March 2011 was observed with ground-based in situ and remote sensing observations to investigate the relationship between visibility and radar reflectivity. The fog layer thickness was less than 200 m. Radar reflectivity values did not exceed ?25 dBZ even with visibilities less than 100 m. The onset and evaporation of fog produce different radar reflectivity?visibility relationships. The evolution of the fog layer was modeled with a droplet activation model that used the aerosol size distribution observed at the 60-m altitude tower level as input. Radar reflectivity and visibility were calculated from model drop size spectra using Mie scattering theory. Since radiative cooling rates are small in comparison with cooling rates due to adiabatic lift of aerosol-laden air, the modeled supersaturation remains low so that few aerosol particles are activated to cloud droplets. The modeling results suggest that the different radar reflectivity?visibility relationships are the result of differences in the interplay between water vapor and cloud droplets during formation and evaporation of the fog. During droplet activation, only a few large cloud droplets remain after successfully competing for water vapor with the smaller activated droplets. These small droplets eventually evaporate (deactivate) again. In the fog dissolution/evaporation stage, only these large droplet need to be evaporated. Therefore, to convert radar reflectivity to visibility for traffic safety products, knowledge of the state of local fog evolution is necessary.
    publisherAmerican Meteorological Society
    titleGround-Based Observations and Modeling of the Visibility and Radar Reflectivity in a Radiation Fog Layer
    typeJournal Paper
    journal volume30
    journal issue2
    journal titleJournal of Atmospheric and Oceanic Technology
    identifier doi10.1175/JTECH-D-12-00081.1
    journal fristpage288
    journal lastpage300
    treeJournal of Atmospheric and Oceanic Technology:;2012:;volume( 030 ):;issue: 002
    contenttypeFulltext
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    DSpace software copyright © 2002-2015  DuraSpace
    نرم افزار کتابخانه دیجیتال "دی اسپیس" فارسی شده توسط یابش برای کتابخانه های ایرانی | تماس با یابش
    yabeshDSpacePersian