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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 10, issue 3 | Copyright
Atmos. Meas. Tech., 10, 1169-1179, 2017
https://doi.org/10.5194/amt-10-1169-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 21 Mar 2017

Research article | 21 Mar 2017

Pyranometer offsets triggered by ambient meteorology: insights from laboratory and field experiments

Sandro M. Oswald1,2,3, Helga Pietsch2, Dietmar J. Baumgartner4, Philipp Weihs3, and Harald E. Rieder1,2,5 Sandro M. Oswald et al.
  • 1Wegener Center for Climate and Global Change, Graz, Austria
  • 2Institute for Geophysics, Astrophysics and Meteorology, Institute of Physics, Graz, Austria
  • 3Institute of Meteorology, University of Natural Resources and Life Sciences (BOKU), Vienna, Austria
  • 4Kanzelhöhe Observatory for Solar and Environmental Research, Graz, Austria
  • 5Austrian Polar Research Institute, Vienna, Austria

Abstract. This study investigates the effects of ambient meteorology on the accuracy of radiation (R) measurements performed with pyranometers contained in various heating and ventilation systems (HV-systems). It focuses particularly on instrument offsets observed following precipitation events. To quantify pyranometer responses to precipitation, a series of controlled laboratory experiments as well as two targeted field campaigns were performed in 2016. The results indicate that precipitation (as simulated by spray tests or observed under ambient conditions) significantly affects the thermal environment of the instruments and thus their stability. Statistical analyses of laboratory experiments showed that precipitation triggers zero offsets of −4W m−2 or more, independent of the HV-system. Similar offsets were observed in field experiments under ambient environmental conditions, indicating a clear exceedance of BSRN (Baseline Surface Radiation Network) targets following precipitation events. All pyranometers required substantial time to return to their initial signal states after the simulated precipitation events. Therefore, for BSRN-class measurements, the recommendation would be to flag the radiation measurements during a natural precipitation event and 90min after it in nighttime conditions. Further daytime experiments show pyranometer offsets of 50W m−2 or more in comparison to the reference system. As they show a substantially faster recovery, the recommendation would be to flag the radiation measurements within a natural precipitation event and 10min after it in daytime conditions.

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This study investigates effects of precipitation events on the accuracy of solar radiation measurements. To quantify pyranometer responses to precipitation, a series of controlled laboratory experiments and two field campaigns were performed. The results indicate that precipitation significantly affects the thermal environment of the instruments and thus their stability. A high accuracy of solar radiation measurements is important to improve the prediction of Earth's climate change.
This study investigates effects of precipitation events on the accuracy of solar radiation...
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