Skip to main content

A century of apparent atmospheric transmission over Davos, Switzerland

We’re sorry, something doesn't seem to be working properly.

Please try refreshing the page. If that doesn't work, please contact support so we can address the problem.


Pyrheliometer measurements have been carried out at the Physikalisches-Meteorologisches Observatorium Davos from 1909 to present which results in the longest stationary direct irradiance record worldwide. A variety of different instruments and measurement scales were homogenized and adjusted to the World Radiometric Reference. Following the pyrheliometric ratioing technique, a time–series of apparent atmospheric transmission was calculated and analyzed for possible trends in column transparency over Davos. In order to assess the trend found in the transmission record, the long-term annual cycle in apparent atmospheric transmission was used to deseasonalize the daily transmission data. The trends of early brightening, dimming and brightening were localized and found to be small but highly significant.

This is a preview of subscription content, access via your institution.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10


  1. Dorno C (1911) Studie über Licht und Luft des Hochgebirges. Vieweg

  2. Dorno C (1919) Physik der Sonnen- und Himmelsstrahlung. Strahlentherapie IX:489–491

  3. Dorno C (1922) Progress in radiation measurements. Monthly Weather Review 50:515–521

    Article  Google Scholar 

  4. Ellis H, Pueschel R (1971) Solar radiation: absence of air pollution trends at Mauna Loa. Science 172:845–846

    Article  Google Scholar 

  5. Fröhlich C (1991) History of solar radiometry and the world radiometric reference. Metrologia 28:111–115

    Article  Google Scholar 

  6. Gueymard C (2001) Parameterized transmittance model for direct beam and circumsolar spectral irradiance. Solar Energy 71:325–346

    Article  Google Scholar 

  7. Hoyt D (1981) Apparent atmospheric transmission using the pyrheliometric ratioing technique. J Appl Optics 18(15):2530–2531

    Article  Google Scholar 

  8. Hoyt D, Fröhlich C (1983) Atmospheric transmission at Davos, Switzerland 1909–1979. Climate Change 5:61–71

    Article  Google Scholar 

  9. Kasten F, Young AT (1989) Revised optical air mass tables and approximation formula. Appl Optics 28:4735–4738

    Article  Google Scholar 

  10. Mörikofer W (1932) Neue Vergleichungen zwischen dem silver-disk-pyrheliometer und dem Angström-pyrheliometer. Internat Strahlungskommission, Anlage V: 43–44

  11. Ohvril H et al (2009) Global dimming and brightening versus atmospheric column transparency, Europe, 1906–2007. J Geophys Res 114:1–17, D00D12

    Article  Google Scholar 

  12. Wild M (2009) Global dimming and brightening: a review. J Geophys Res 114:1–31, D00D16

    Google Scholar 

  13. Wild M, Ohmura A et al (2005) From dimming to brightening: decadal changes in solar radiation at earth's surface. Science 308:847–850

    Article  Google Scholar 

  14. WMO (2008) Guide to meteorological instruments and methods of observations. WMO-No. 8 (Seventh edition)

Download references


The support from the Swiss National Science Foundation (grant #200021-124924), as well as the constructive comments by two anonymous reviewers is acknowledged. Meteorological data were kindly provided by MeteoSwiss.

Author information



Corresponding authors

Correspondence to D. Lachat or C. Wehrli.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Lachat, D., Wehrli, C. A century of apparent atmospheric transmission over Davos, Switzerland. Theor Appl Climatol 110, 539–547 (2012).

Download citation


  • Atmospheric Transmission
  • Surface Solar Radiation
  • Irradiance Data
  • Transmission Series
  • Direct Irradiance