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A century of apparent atmospheric transmission over Davos, Switzerland

Abstract

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.

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Acknowledgments

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.

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Correspondence to D. Lachat or C. Wehrli.

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Lachat, D., Wehrli, C. A century of apparent atmospheric transmission over Davos, Switzerland. Theor Appl Climatol 110, 539–547 (2012). https://doi.org/10.1007/s00704-012-0685-z

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Keywords

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