Preprints
https://doi.org/10.5194/amt-2021-398
https://doi.org/10.5194/amt-2021-398

  29 Nov 2021

29 Nov 2021

Review status: this preprint is currently under review for the journal AMT.

Airborne measurements of directional reflectivity over the marginal sea ice zone

Sebastian Becker1, André Ehrlich1, Evelyn Jäkel1, Tim Carlsen2, Michael Schäfer1, and Manfred Wendisch1 Sebastian Becker et al.
  • 1Leipzig Institute for Meteorology (LIM), Universität Leipzig, Leipzig, Germany
  • 2Department of Geosciences, University of Oslo, Oslo, Norway

Abstract. The directional reflection of solar radiation by the Arctic Ocean is dominated by two main surface types: sea ice (often snow-covered) and ice-free (open) ocean. However, in the transitional marginal sea ice zone (MIZ), the reflection properties of both surface types are mixed, which might cause uncertainties in the results of retrieval methods of atmospheric parameters over the MIZ using airborne and satellite measurements. To quantify these uncertainties, respective measurements of reflection properties of the MIZ are needed. Therefore, in this study, an averaged hemispherical-directional reflectance factor (HDRF) of the inhomogeneous surface (mixture of sea ice and open ocean surfaces) in the MIZ is derived using airborne measurements collected with a digital fish-eye camera. For this purpose, a sea ice mask was constructed to separate the reflectivity measurements from sea ice and open ocean pixels. The separated data sets were accumulated and averaged to provide separate HDRFs for sea ice and open ocean surfaces. The respective results were compared with simulations and independent measurements available from the literature. Using the sea ice fraction derived in parallel from the digital camera images, the mixed HDRF describing the directional reflectivity of the inhomogeneous surface of the MIZ was reconstructed by a linear weighting procedure. The result was compared with the original measurements of directional reflectivity over the MIZ. It is concluded that the HDRF of the MIZ can be well reconstructed by linear combination of the HDRFs of homogeneous sea ice and open ocean surfaces, accounting for the special conditions present in the MIZ compared to homogeneous surfaces.

Sebastian Becker et al.

Status: open (until 10 Feb 2022)

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Sebastian Becker et al.

Sebastian Becker et al.

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Short summary
Airborne radiation measurements are used to characterize the solar directional reflection of a mixture of Arctic sea ice and open ocean surfaces in the transition zone between both surface types. The mixture reveals reflection properties of both surface types. It is shown that the directional reflection of the mixture can be reconstructed from the directional reflection of the individual surfaces accounting for the special conditions present in the transition zone.