Spectral distribution of solar radiation. I: Direct radiation

Abstract

SUMMARYMeasurements of the spectral distribution of direct solar radiation, made in both wide and narrow wavebands, are reported. The measurements suggest that the wavelength dependence of aerosol attenuation in central England, in summer, can generally be described by a power law with wavelength exponent of about 1.7. Attenuation of visible radiation is reported in terms of an integral turbidity coefficient, 7", and is shown to depend to some extent on air mass origin, air masses from the continent being more turbid than maritime air masses. The mean value of t, is 0 3 1 with a range of 0 0 5 to 0 6 . The ratio of visible to total direct irradiance is found to be a linear function of t", the constants of linearity being functions of zenith angle. From these relationships a semi-empirical model is developed enabling spectral irradiance, visible irradiance and total solar irradiance to be estimated from arbitrary values of turbidity and zenith angle.

Reflexion and absorption of solar radiation by flowering canopies of oil-seed rape (Brassica napus L.)

“…Measurements of canopy reflectivity and transmissivity spectra were made at 20 nm intervals for spectral bandwidths 10 nm wide from 400 to .800 nm with a spectroradiometer (Gamma Scientific) equipped with a 2 m fibre-optic extension and cosinecorrecting head (McCartney & Unsworth, 1978). The incident solar spectrum was measured before and after each canopy spectrum to provide a reference.…”

Solar Spectral Measurements and Modeling

“…Many rigorous radiative transfer codes have been formulated over the years, but as far as we can determine, none of them has been properly verified with speetml data. Although many research facilities have measured solar spectra [1][2][3][4][5][6][7][8][9], these have not been used for model verification. One serious limitation of seveml existing spectra is that adequate measurements of meteorological conditions do not accompany them.…”

Μελέτη Των Φυσικών Και Οπτικών Ιδιοτήτων Στην Ατμόσφαιρα Της Αθήνας

“…Οι πιο συνηθισμένες παράμετροι θόλωσης που έχουν χρησιμοποιηθεί ευρέως είναι αυτές που προτάθηκαν από τον Angstrom (Angstrom, 1929(Angstrom, 1930. Στη διεθνή βιβλιογραφία εμφανίζονται πολλές μελέτες με διάφορες μεθοδολογίες οι οποίες καθορίζουν τις τιμές των παραμέτρων α και β (Volz, 1974McCartney and Unsworth, 1978Castro, 1982Cachorro et al, 1987of β Louche et al, 1987Wahab, 1993Trier and Horvath, 1993Pinazo et al, 1995Adeyefa and Holmgren, 1996Adeyefa et al, 1997Bokoye et al, 1997Tornasi et al, 1997Gueymard, 1998Pedros et al, 1999.…”

“…Κάποιες από αυτές αφορούν μελέτες σε στενές φασματικές περιοχές στην υπεριώδη και ορατή περιοχή (π.χ. McCartney and Unsworth, 1978Cachorro et al, 1987οί Lorente et al, 1994Adeyefa et al, 1997Kambezidis et al, 1997/3 Marenco et al, 1997 (Junge, 1955(Junge, 1963 Holmgren, 1996' Adeyefa et al, 1997). Οι Cachorro et al (1987α) (1,9.3,5) που τελικά οδηγεί στη σχέση (1,9.3.4) (Angstrom, 1961 (Yamamoto and Tanaka, 1969King et ai., 1978Tanré et al, 1988Schmid et al, 1997, Στην παρούσα εργασία, χρησιμοποιήθηκε η τεχνική ελαχιστοποίησης (minimization technique), βασισμένη στην έρευνα της χρυσής τομής (golden section search) (Cheney and Kincaid, 1998) της διαφοράς μεταξύ πειραματικών και θεωρητικών τιμών της οπτικής πυκνότητας (Cachorro et al, 1999).…”