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
Received: 10 Aug 2016 – Discussion started: 26 Sep 2016
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.
Revised: 29 Nov 2016 – Accepted: 02 Dec 2016 – Published: 20 Dec 2016
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.