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Illuminance turbidity parameters and atmospheric extinction in the visible spectrum
Author(s) -
Gueymard C.,
Kambezidis H. D.
Publication year - 1997
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49712353908
Subject(s) - illuminance , irradiance , aerosol , photometer , radiometer , sun photometer , environmental science , turbidity , optics , remote sensing , extinction (optical mineralogy) , atmospheric sciences , actinometer , infrared window , physics , meteorology , infrared , geology , oceanography , plasma , quantum mechanics
Expressions for the Linke, T Li , and Unsworth‐Monteith, T Ui , turbidity parameters in the visible region of the solar spectrum are derived for application in illumination studies. They are based on new determinations of the visible transmittances of various atmospheric constituents, obtained by spectrally integrating the atmospheric transmittances calculated with a spectral irradiance research code. the influence of pressure, of circumsolar radiation, and of different atmospheric constituents (including both stratospheric and tropospheric nitrogen dioxide) on the interpretation of turbidity is discussed. T Ui is shown to be virtually free of parasitic variations with air mass or other factors, and to approximate the aerosol optical thickness at 555 nm quite closely. The experimental T Ui has been obtained from measurements of direct illuminance for two days at Albany, New York, and compared to the aerosol optical thickness measured with a multiwavelength radiometer. the observed fair agreement between T Ui and the experimental optical thickness at 555 nm suggests that the latter may be accurately approximated by the former, using equipment that can be easily calibrated in the laboratory—unlike sun photometers. the use of T Ui in subsequent measurement campaigns is recommended rather than that of T Li .