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Il Nuovo Cimento C

, Volume 5, Issue 2, pp 223–246 | Cite as

Evaluation of the atmospheric content of particulate mass from visibility observations

  • C. Tomasi
Article

Summary

Accurate estimates of the average value of the atmospheric extinction coefficient in the visible spectral range can be obtained from observations of visibility if they are carefully made according to Horvath's criteria. Since the perception function depends on the spectral features of atmospheric attenuation and illumination, the average coefficients due to Rayleigh scattering and to absorption by water vapour, ozone and nitrogen dioxide are evaluated as a function of the wave-length of maximum perception. Thus, the average extinction coefficient by particulate matter can be obtained as the difference between the average value of the atmospheric extinction coefficient and the sum of the various coefficients given by Rayleigh scattering and absorption by minor gases. From this evaluation, the mass content of particulate matter along the horizontal path at ground level can be estimated by making use of a large set of mass extinction coefficients obtained for different models of both airborne particles and water droplets and calculated at the wave-length of maximum perception for various turbidity conditions.

Keywords

Ozone Rayleigh Scattering Nitrogen Dioxide Visible Spectral Range Perception Function 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Riassunto

Stime accurate del valore medio del coefficiente di estinzione atmosferical nel visibile possono essere ottenute da osservazioni di visibilità, se queste sono fatte accuratamente secondo i criteri suggeriti da Horvath. Poiché la funzione di percezione varia in funzione delle caratteristiche spettrali di attenuazione atmosferica e d'illuminazione, si sono valuatati i coefficienti medi dovuti allo scattering di Rayleigh e all'assorbimento da vapor d'acqua, da ozono e da biossido di azoto in funzione della lunghezza d'onda di massima percezione. Allora, si può calcolare il coefficiente medio di estinzione delle particelle atmosferiche come differenza tra il coefficiente medio di estinzione atmosferica e la somma dei vari coefficienti prodotti dallo scattering di Rayleigh e dall'assorbimento dei gas atmosferici minori. Da questa valutazione, si può ottenere una stima del contenuto di massa delle particelle lungo il percorso orizzontale al suolo, facendo uso di un ampio insieme di coefficienti di estinzione per unità di massa ottenuti per diversi modelli di particelle atmosferiche e di goccioline d'acqua e calcolati alla lunghezza d'onda di massima percezione per differenti condizioni di torbidità atmosferica.

Резюме

Точные оценки средней велины козффициента атмосферной экстинкции в видимой спектральной области могут быть получены из наблюдений видимости, если эти наблюдения проводятся в соответствии с критериями Хорвата. Так как функция восприятия зависит от спектральных особенностей атмосферного ослабления и освешенности, то средние коэффициенты, обусловленные релеевским рассеянием и поглошением в водяном паре, озоне и двуокиси азота, оцениваются как функция длины волны для максимального восприятия. Таким образом, средний коэффициент экстинкции, обусловленный микрочастицами, может быть получен как разность между средней величиной атмосферного коэффипиента экстинкции и суммы различных коэффициентов, задаваемых релеевским рассеянием и поглощением в менее существенных газах. Из этой оценки может быть получено массовое содержание микрочастиц вещества вдоль горизонтального пути на уровне Земли, используя большую систему массовых козффициентов зкстинкции, полученных для различных моделей находящихся в воздухе частиц и водяных капель и вычисленных на длине волны максимального восприятия для различных условий помутнения.

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Copyright information

© Società Italiana di Fisica 1982

Authors and Affiliations

  • C. Tomasi
    • 1
  1. 1.Istituto FISBATC.N.R.BolognaItalia

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