Articles | Volume 12, issue 14
Atmos. Chem. Phys., 12, 6157–6172, 2012
Atmos. Chem. Phys., 12, 6157–6172, 2012

Research article 17 Jul 2012

Research article | 17 Jul 2012

Aerosol observations and growth rates downwind of the anvil of a deep tropical thunderstorm

D. A. Waddicor1, G. Vaughan1, T. W. Choularton1, K. N. Bower1, H. Coe1, M. Gallagher1, P. I. Williams1, M. Flynn1, A. Volz-Thomas2, H. -W. Pätz2, P. Isaac3, J. Hacker3, F. Arnold4, H. Schlager5, and J. A. Whiteway6 D. A. Waddicor et al.
  • 1School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, UK
  • 2Forschungszentrum Jülich, Germany
  • 3Flinders University, Adelaide, Australia
  • 4Max-Planck-Institute for Nuclear Physics, Heidelberg, Germany
  • 5Deutsches Zentrum für Luft- und Raumfahrt, Oberpfaffenhofen, Germany
  • 6Centre for Research in Earth and Space Sciences, York University, Toronto, Canada

Abstract. We present a case study of Aitken and accumulation mode aerosol observed downwind of the anvil of a deep tropical thunderstorm. The measurements were made by condensation nuclei counters flown on the Egrett high-altitude aircraft from Darwin during the ACTIVE campaign, in monsoon conditions producing widespread convection over land and ocean. Maximum measured concentrations of aerosol with diameter greater than 10 nm were 25 000 cm−3 (STP). By calculating back-trajectories from the observations, and projecting onto infrared satellite images, the time since the air exited cloud was estimated. In this way a time scale of about 3 hours was derived for the Aitken aerosol concentration to reach its peak. We examine the hypothesis that the growth in aerosol concentrations can be explained by production of sulphuric acid from SO2 followed by particle nucleation and coagulation. Estimates of the sulphuric acid production rate show that the observations are only consistent with this hypothesis if the particles coagulate to sizes >10 nm much more quickly than is suggested by current theory. Alternatively, other condensible gases (possibly organic) drive the growth of aerosol particles in the TTL.

Final-revised paper