Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 16, 15689-15707, 2016
http://www.atmos-chem-phys.net/16/15689/2016/
doi: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
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 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.

Citation: Libois, Q., Ivanescu, L., Blanchet, J.-P., Schulz, H., Bozem, H., Leaitch, W. R., Burkart, J., Abbatt, J. P. D., Herber, A. B., Aliabadi, A. A., and Girard, É.: Airborne observations of far-infrared upwelling radiance in the Arctic, Atmos. Chem. Phys., 16, 15689-15707, doi:10.5194/acp-16-15689-2016, 2016.
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Short summary
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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