Il Nuovo Cimento C

, Volume 17, Issue 4, pp 407–430 | Cite as

Characterization of Ångström's turbidity parameters in the Po Valley area for summer conditions of the atmosphere

  • L. V. De Santis
  • C. Tomasi
  • V. Vitale
Article
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Accepted:

Summary

Measurements of direct solar irradiance were taken at the San Pietro Capofiume station in the centre of the Po Valley using two examples of the multispectral sun photometer, model UVISIR, on several clear-sky days of late spring and early summer in the years 1989 and 1990. Realistic evaluations of aerosol optical thickness at several sun-photometric wavelengths were obtained from these measurements by i) using values of the calibration constants carefully found by following both the Langley plot method and the spectral-correction procedure, which had previously been applied with satisfactory results to the sun-photometric measurements carried out in Antarctica and ii) taking into account the extinction effects produced by Rayleigh scattering and absorption due to ozone, water vapour and nitrogen dioxide on the solar radiation passing through the atmosphere. By examining a wide set of spectral series of the aerosol optical thickness in terms of the well-known Ångström formula, a large number of pairs of atmospheric-turbidity parameters α and β was obtained, presenting a range of the mean daily values of α from 1.0 to 1.7 (with the median of 1.48) and a range of the mean daily values of β from 0.10 to 0.30 (with the median of 0.15). Using the particulate extinction models CR (for continental particles) and TR (for small tropospheric particles and large rural particles), the aerosol mass loading of the atmosphere calculated for these values of α and β was estimated to vary between 0.09 and 0.31 g m−2 (with the median of 0.21 g m−2) during the measurement period of 1989 and between 0.09 and 0.41 g m−2 (with the median of 0.13 g m−2 for model CR and of 0.21 g m−2 for model TR) during June and July 1990.

PACS 01.30.Cc

Conference proceedings 

PACS 92.60

Meteorology 

PACS 42.68

Atmospheric optics 
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Copyright information

© Società Italiana di Fisica 1994

Authors and Affiliations

  • L. V. De Santis
    • 1
    • 2
  • C. Tomasi
    • 1
  • V. Vitale
    • 1
  1. 1.Istituto FISBAT del CNRBolognaItalia
  2. 2.Istituto ISIATA del CNRLecceItalia

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