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The Cryosphere An interactive open-access journal of the European Geosciences Union
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Volume 10, issue 2
The Cryosphere, 10, 775-790, 2016
https://doi.org/10.5194/tc-10-775-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
The Cryosphere, 10, 775-790, 2016
https://doi.org/10.5194/tc-10-775-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 06 Apr 2016

Research article | 06 Apr 2016

Correction of broadband snow albedo measurements affected by unknown slope and sensor tilts

Ursula Weiser1, Marc Olefs1, Wolfgang Schöner2, Gernot Weyss1, and Bernhard Hynek1 Ursula Weiser et al.
  • 1Central Institute for Meteorology and Geodynamics (ZAMG), Vienna, Austria
  • 2Institute of Geography and Regional Research, University of Graz, Graz, Austria

Abstract. Geometric effects induced by the underlying terrain slope or by tilt errors of the radiation sensors lead to an erroneous measurement of snow or ice albedo. Consequently, artificial diurnal albedo variations in the order of 1–20% are observed. The present paper proposes a general method to correct tilt errors of albedo measurements in cases where tilts of both the sensors and the slopes are not accurately measured or known. We demonstrate that atmospheric parameters for this correction model can either be taken from a nearby well-maintained and horizontally levelled measurement of global radiation or alternatively from a solar radiation model. In a next step the model is fitted to the measured data to determine tilts and directions of sensors and the underlying terrain slope. This then allows us to correct the measured albedo, the radiative balance and the energy balance. Depending on the direction of the slope and the sensors a comparison between measured and corrected albedo values reveals obvious over- or underestimations of albedo. It is also demonstrated that differences between measured and corrected albedo are generally highest for large solar zenith angles.

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Geometric effects induced by tilt errors lead to erroneous measurement of snow albedo. These errors are corrected where tilts of sensors and slopes are unknown. Atmospheric parameters are taken from a nearby reference measurement or a radiation model. The developed model is fitted to the measured data to determine tilts and directions which vary daily due to changing atmospheric conditions and snow cover. The results show an obvious under- or overestimation of albedo depending on the slope direction.
Geometric effects induced by tilt errors lead to erroneous measurement of snow albedo. These...
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