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Volume 16, issue 24
Atmos. Chem. Phys., 16, 15689–15707, 2016
https://doi.org/10.5194/acp-16-15689-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: NETCARE (Network on Aerosols and Climate: Addressing Key Uncertainties...

Atmos. Chem. Phys., 16, 15689–15707, 2016
https://doi.org/10.5194/acp-16-15689-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 20 Dec 2016

Research article | 20 Dec 2016

Airborne observations of far-infrared upwelling radiance in the Arctic

Quentin Libois1, Liviu Ivanescu1,2, Jean-Pierre Blanchet1, Hannes Schulz3, Heiko Bozem4, W. Richard Leaitch5, Julia Burkart6, Jonathan P. D. Abbatt6, Andreas B. Herber3, Amir A. Aliabadi7, and Éric Girard1 Quentin Libois et al.
  • 1Department of Earth and Atmospheric Sciences, Université du Québec à Montréal, Montréal, Canada
  • 2Centre d'applications et de recherches en télédétection (CARTEL), Université de Sherbrooke, Sherbrooke, Canada
  • 3Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, Bremerhaven, Germany
  • 4Johannes Gutenberg University of Mainz, Institute for Atmospheric Physics, Mainz, Germany
  • 5Environment and Climate Change Canada, Toronto, Canada
  • 6Department of Chemistry, University of Toronto, Toronto, Canada
  • 7Atmospheric Innovations Research (AIR) Laboratory, School of Engineering, University of Guelph, Guelph, Canada

Abstract. The first airborne measurements of the Far-InfraRed Radiometer (FIRR) were performed in April 2015 during the panarctic NETCARE campaign. Vertical profiles of spectral upwelling radiance in the range 8–50 µm were measured in clear and cloudy conditions from the surface up to 6 km. The clear sky profiles highlight the strong dependence of radiative fluxes to the temperature inversion typical of the Arctic. Measurements acquired for total column water vapour from 1.5 to 10.5 mm also underline the sensitivity of the far-infrared greenhouse effect to specific humidity. The cloudy cases show that optically thin ice clouds increase the cooling rate of the atmosphere, making them important pieces of the Arctic energy balance. One such cloud exhibited a very complex spatial structure, characterized by large horizontal heterogeneities at the kilometre scale. This emphasizes the difficulty of obtaining representative cloud observations with airborne measurements but also points out how challenging it is to model polar clouds radiative effects. These radiance measurements were successfully compared to simulations, suggesting that state-of-the-art radiative transfer models are suited to study the cold and dry Arctic atmosphere. Although FIRR in situ performances compare well to its laboratory performances, complementary simulations show that upgrading the FIRR radiometric resolution would greatly increase its sensitivity to atmospheric and cloud properties. Improved instrument temperature stability in flight and expected technological progress should help meet this objective. The campaign overall highlights the potential for airborne far-infrared radiometry and constitutes a relevant reference for future similar studies dedicated to the Arctic and for the development of spaceborne instruments.

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The first airborne measurements performed with the FIRR are presented. Vertical profiles of upwelling spectral radiance in the far-infrared are measured in the Arctic atmosphere for the first time. They show the impact of the temperature inversion on the radiative budget of the atmosphere, especially in the far-infrared. The presence of ice clouds also significantly alters the far-infrared budget, highlighting the critical interplay between water vapour and clouds in this very dry region.
The first airborne measurements performed with the FIRR are presented. Vertical profiles of...
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