Articles | Volume 15, issue 14
Atmos. Chem. Phys., 15, 8479–8520, 2015
Atmos. Chem. Phys., 15, 8479–8520, 2015

Research article 30 Jul 2015

Research article | 30 Jul 2015

Advances in understanding mineral dust and boundary layer processes over the Sahara from Fennec aircraft observations

C. L. Ryder1, J. B. McQuaid2,6, C. Flamant3, P. D. Rosenberg2, R. Washington4, H. E. Brindley5, E. J. Highwood1, J. H. Marsham2,6, D. J. Parker2, M. C. Todd7, J. R. Banks5, J. K. Brooke2,8, S. Engelstaedter4, V. Estelles9,a, P. Formenti10, L. Garcia-Carreras2, C. Kocha3, F. Marenco8, H. Sodemann11,b, C. J. T. Allen4, A. Bourdon12, M. Bart2,c, C. Cavazos-Guerra7,d, S. Chevaillier10, J. Crosier13, E. Darbyshire1,13, A. R. Dean14, J. R. Dorsey13, J. Kent8, D. O'Sullivan8, K. Schepanski2,e, K. Szpek8, J. Trembath14, and A. Woolley14 C. L. Ryder et al.
  • 1Department of Meteorology, University of Reading, Reading, RG6 6BB, UK
  • 2School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
  • 3Sorbonne Universités, UPMC, Université Paris 06, CNRS & UVSQ, UMR 8190 LATMOS, Paris, France
  • 4School of Geography and the Environment, University of Oxford, Oxford, UK
  • 5Space and Atmospheric Physics, Department of Physics, Imperial College London, London, UK
  • 6National Centre for Atmospheric Science, University of Leeds, Leeds, LS2 9JT, UK
  • 7Department of Geography, University of Sussex, Brighton BN1 9QJ, UK
  • 8Met Office, Exeter, EX1 3PB, UK
  • 9Dept. Física Fundamental y Experimental, Electrónica y Sistemas, Universidad de La Laguna, San Cristóbal de La Laguna, Spain
  • 10LISA, UMR CNRS 7583, Université Paris Est Créteil et Université Paris Diderot, Institut Pierre Simon Laplace, Créteil, France
  • 11Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
  • 12SAFIRE, UMS CNRS-CNES-Météo-France, Francazal, France
  • 13National Centre for Atmospheric Science, University of Manchester, Manchester, M13 9PL, UK
  • 14Facility for Airborne Atmospheric Measurements, Cranfield, MK43 0AL, UK
  • anow at: Department of Earth Physics and Thermodynamics, Universitat de València, Santa Cruz de Tenerife, Spain
  • bnow at: Geophysical Institute, University of Bergen, Bergen, Norway
  • cnow at: Aeroqual Ltd, 109 Valley Road, Auckland, New Zealand
  • dnow at: Institute for Advanced Sustainability Studies (IASS), Berliner Straße 130, 14467 Potsdam, Germany
  • enow at: Leibniz Institute for Tropospheric Research, Permoserstr. 15, 04318 Leipzig, Germany

Abstract. The Fennec climate programme aims to improve understanding of the Saharan climate system through a synergy of observations and modelling. We present a description of the Fennec airborne observations during 2011 and 2012 over the remote Sahara (Mauritania and Mali) and the advances in the understanding of mineral dust and boundary layer processes they have provided. Aircraft instrumentation aboard the UK FAAM BAe146 and French SAFIRE (Service des Avions Français Instrumentés pour la Recherche en Environnement) Falcon 20 is described, with specific focus on instrumentation specially developed for and relevant to Saharan meteorology and dust. Flight locations, aims and associated meteorology are described. Examples and applications of aircraft measurements from the Fennec flights are presented, highlighting new scientific results delivered using a synergy of different instruments and aircraft. These include (1) the first airborne measurement of dust particles sizes of up to 300 microns and associated dust fluxes in the Saharan atmospheric boundary layer (SABL), (2) dust uplift from the breakdown of the nocturnal low-level jet before becoming visible in SEVIRI (Spinning Enhanced Visible Infra-Red Imager) satellite imagery, (3) vertical profiles of the unique vertical structure of turbulent fluxes in the SABL, (4) in situ observations of processes in SABL clouds showing dust acting as cloud condensation nuclei (CCN) and ice nuclei (IN) at −15 °C, (5) dual-aircraft observations of the SABL dynamics, thermodynamics and composition in the Saharan heat low region (SHL), (6) airborne observations of a dust storm associated with a cold pool (haboob) issued from deep convection over the Atlas Mountains, (7) the first airborne chemical composition measurements of dust in the SHL region with differing composition, sources (determined using Lagrangian backward trajectory calculations) and absorption properties between 2011 and 2012, (8) coincident ozone and dust surface area measurements suggest coarser particles provide a route for ozone depletion, (9) discrepancies between airborne coarse-mode size distributions and AERONET (AERosol Robotic NETwork) sunphotometer retrievals under light dust loadings. These results provide insights into boundary layer and dust processes in the SHL region – a region of substantial global climatic importance.

Short summary
Measurements of the Saharan atmosphere and of atmospheric mineral dust are lacking but are vital to our understanding of the climate of this region and their impacts further afield. Novel observations were made by the Fennec climate programme during June 2011 and 2012 using ground-based, remote sensing and airborne platforms. Here we describe the airborne observations and the contributions they have made to furthering our understanding of the Saharan climate system.
Final-revised paper