A numerical study of tropical cross-tropopause transport by convective overshoots J.-P. Chaboureau1, J.-P. Cammas1, J. Duron1, P. J. Mascart1, N. M. Sitnikov2, and H.-J. Voessing3 1Laboratoire d'Aérologie, Université Paul Sabatier and CNRS, Toulouse, France 2Central Aerological Observatory, Dolgoprudny, Russia 3Institute for Atmospheric Physics, University of Mainz, Germany
Abstract. Observations obtained during the Tropical Convection, Cirrus and Nitrogen
Oxides (TROCCINOX) golden day have revealed the presence of ice particles up
to 410 K (18.2 km) 2 km above the local tropopause. The
case was investigated using a three-dimensional quadruply nested
non-hydrostatic simulation and Meteosat Second Generation (MSG) observations.
The simulation reproduced the measurements along the flight
track fairly well. A reasonable agreement with MSG observations was also achieved: the
10.8-μm brightness temperature (BT) minimum of 187 K was
reproduced (a value 6 K colder than the environmental cold-point
temperature) as was the positive BT difference between the 6.2- and
10.8-μm bands, an overshoot signature. The simulation produced
several overshooting plumes up to 410 K yielding an upward transport
of water vapour of a few tons per second across the tropical tropopause. The
estimated mass flux agrees with those derived from over tracer budgets,
indicating that convection transports mass across the tropopause.
Citation: Chaboureau, J.-P., Cammas, J.-P., Duron, J., Mascart, P. J., Sitnikov, N. M., and Voessing, H.-J.: A numerical study of tropical cross-tropopause transport by convective overshoots, Atmos. Chem. Phys., 7, 1731-1740, doi:10.5194/acp-7-1731-2007, 2007.