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Area Lighting / Visual signalling

IEV ref845-11-20

Symbol
ν

en
meteorological optical range
length of the path in the atmosphere that is required to attenuate by 95 % the luminous flux in a collimated beam from a light source at a colour temperature of 2700 K

Note 1 – The value of the attenuation has been chosen so that the term provides an approximate measure of the commonly used concept of (meteorological) visibility, which is the greatest distance at which a black object of suitable dimensions can be recognized by day against the horizon sky.

Note 2 – The meteorological optical range ν is related to the atmospheric transmissivity T, assumed to be uniform, by the formula

v= d 0 log0,05 logT MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGe aGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaq Fn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpe WZqaaeaaciWacmGadaGadeaabaGaaqaaaOqaaiaadAhacqGH9aqpca WGKbWaaSbaaSqaaiaaicdaaeqaaOWaaSaaaeaaciGGSbGaai4Baiaa cEgacaaMe8UaaGimaiaac6cacaaIWaGaaGynaaqaaiGacYgacaGGVb Gaai4zaiaadsfaaaaaaa@4425@ or T= 0,05 d 0 /v MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGe aGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaq Fn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpe WZqaaiqaciWacmGadaGadeaabaGaaqaaaOqaaiaadsfacqGH9aqpca aIWaGaaiOlaiaaicdacaaI1aWaaWbaaSqabeaadaWcgaqaaiaadsga daWgaaadbaGaaGimaaqabaaaleaacaWG2baaaaaaaaa@3D2F@

where d0 is the length specified in the definition of T.
These formulas are sometimes written

v= log0,05 logT MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGe aGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaq Fn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpe WZqaaeaaciWacmGadaGadeaabaGaaqaaaOqaaiaadAhacqGH9aqpda WcaaqaaiGacYgacaGGVbGaai4zaiaaysW7caaIWaGaaiOlaiaaicda caaI1aaabaGaciiBaiaac+gacaGGNbGaamivaaaaaaa@424C@ or T= 0,05 1/v MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGe aGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaq Fn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpe WZqaaiqaciWacmGadaGadeaabaGaaqaaaOqaaiaadsfacqGH9aqpca aIWaGaaiOlaiaaicdacaaI1aWaaWbaaSqabeaadaWcgaqaaiaaigda aeaacaWG2baaaaaaaaa@3C0F@

it being understood that v is the numerical value of the meteorological optical range ν measured with the "unit" d0 and T the numerical value of T.


fr
portée optique météorologique, f
longueur d'un trajet dans l'atmosphère sur lequel le flux lumineux d'un faisceau quasi parallèle de rayonnement, émanant d'une source lumineuse de température de couleur 2700 K, est réduit de 95 %

Note 1 – La valeur de l'atténuation a été choisie de telle sorte que ce terme conduise une mesure approximative de la notion couramment employée de visibilité (météorologique), qui est la plus grande distance à laquelle un objet noir de dimensions convenables peut être reconnu de jour sur le ciel à l'horizon.

Note 2 – La portée optique météorologique ν est reliée à la transmissivité atmosphérique T supposée uniforme par les formules

v= d 0 log0,05 logT MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGe aGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaq Fn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpe WZqaaeaaciWacmGadaGadeaabaGaaqaaaOqaaiaadAhacqGH9aqpca WGKbWaaSbaaSqaaiaaicdaaeqaaOWaaSaaaeaaciGGSbGaai4Baiaa cEgacaaMe8UaaGimaiaac6cacaaIWaGaaGynaaqaaiGacYgacaGGVb Gaai4zaiaadsfaaaaaaa@4425@ ou T= 0,05 d 0 /v MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGe aGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaq Fn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpe WZqaaiqaciWacmGadaGadeaabaGaaqaaaOqaaiaadsfacqGH9aqpca aIWaGaaiOlaiaaicdacaaI1aWaaWbaaSqabeaadaWcgaqaaiaadsga daWgaaadbaGaaGimaaqabaaaleaacaWG2baaaaaaaaa@3D2F@

d0 est la longueur spécifiée pour la définition de T.

Ces formules sont parfois écrites sous la forme

v= log0,05 logT MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGe aGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaq Fn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpe WZqaaeaaciWacmGadaGadeaabaGaaqaaaOqaaiaadAhacqGH9aqpda WcaaqaaiGacYgacaGGVbGaai4zaiaaysW7caaIWaGaaiOlaiaaicda caaI1aaabaGaciiBaiaac+gacaGGNbGaamivaaaaaaa@424C@ ou T= 0,05 1/v MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGe aGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaq Fn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpe WZqaaiqaciWacmGadaGadeaabaGaaqaaaOqaaiaadsfacqGH9aqpca aIWaGaaiOlaiaaicdacaaI1aWaaWbaaSqabeaadaWcgaqaaiaaigda aeaacaWG2baaaaaaaaa@3C0F@

étant sous-entendu que v est la valeur numérique de la portée optique météorologique ν mesurée avec d0 comme "unité" et T la valeur numérique de T.


ar
مدى بصرى للرصد الجوى

de
meteorologisch optische Sichtweite, f

es
alcance óptico meteorológico

fi
optinen meteorologinen näkyvyys

it
portata ottica meteorologica

ko
기상학적 광학거리

ja
気象光学視距離

no
nb meteorologisk lysvidde

nn meteorologisk lysvidde

pl
zasięg meteorologiczny optyczny

pt
alcance óptico meteorológico

sv
meteorologisk lysvidd

Publication date: 1987
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