Airborne DOAS measurements in Arctic: vertical distributions of aerosol extinction coefficient and NO 2 concentration

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Merlaud, A., van Roozendael, M., Theys, N., Fayt, C., Hermans, C., Quennehen, Boris, Schwarzenboeck, Alfons, Ancellet, Gérard, Pommier, Matthieu, Pelon, Jacques, Burkhart, J., Stohl, A., de Mazière, M.
• Other Authors: Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Laboratoire de météorologie physique (LaMP), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), TROPO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Norwegian Institute for Air Research (NILU)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: DOAS instrument; Differential Optical Absorption Spectroscopy; Troposphere; POLARCAT; Azote Dioxide; Arctic; [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; kola peninsula
• Online Access: https://hal.science/hal-00590730; https://hal.science/hal-00590730/document; https://hal.science/hal-00590730/file/acp-11-9219-2011.pdf; https://doi.org/10.5194/acp-11-9219-2011

International audience We report airborne differential optical absorption spectroscopy (DOAS) measurements of aerosol extinction and NO 2 tropospheric profiles performed off the North coast of Norway in April 2008. The DOAS instrument was installed on the Safire ATR-42 aircraft during the POLARCAT-France spring campaign and recorded scattered light spectra in near-limb geometry using a scanning telescope. We use O 4 slant column measurements to derive the aerosol extinction at 360 nm. Regularization is based on the maximum a posteriori solution, for which we compare a linear and a logarithmic approach. The latter inherently constrains the solution to positive values and yields aerosol extinction profiles more consistent with independently measured size distributions. Two soundings are presented, performed on 8 April 2008 above 71° N, 22° E and on 9 April 2008 above 70° N, 17.8° E. The first profile shows aerosol extinction and NO 2 in the marine boundary layer with respective values of 0.04±0.005 km −1 and 1.9±0.3 × 109 molec cm −3 . A second extinction layer of 0.01±0.003 km −1 is found at 4 km altitude. During the second sounding, clouds prevented us to retrieve profile parts under 3 km altitude but a layer with enhanced extinction (0.025±0.005 km −1 ) and NO 2 (1.95±0.2 × 109 molec cm −3 ) is clearly detected at 4 km altitude. From CO and ozone in-situ measurements complemented by back-trajectories, we interpret the measurements in the free troposphere as, for the first sounding, a mix between stratospheric and polluted air from Northern Europe and for the second sounding, polluted air from Central Europe containing NO 2 . Considering the boundary layer measurements of the first flight, modeled source regions indicate closer sources, especially the Kola Peninsula smelters, which can explain the NO 2 enhancement not correlated with a CO increase at the same altitude.