Contribution of mixing to upward transport across the tropical tropopause layer (TTL) P. Konopka1, G. Günther1, R. Müller1, F. H. S. dos Santos1, C. Schiller1, F. Ravegnani2, A. Ulanovsky3, H. Schlager4, C. M. Volk5, S. Viciani6, L. L. Pan7, D.-S. McKenna7, and M. Riese1 1Forschungszentrum Jülich (ICG-1: Stratosphäre), Germany 2CNR-ISAC, Bologna, Italy 3CAO, Dolgoprudny, Russia 4Institut für Physik der Atmosphäre, DLR Oberpfaffenhofen, Germany 5Institut für Meteorologie und Geophysik, Universität Frankfurt, Germany 6INOA, Firenze, Italy 7National Center for Atmospheric Research, Boulder, CO, USA
Abstract. During the second part of the
TROCCINOX campaign that took place in Brazil in early 2005,
chemical species were measured on-board the high-altitude research aircraft
Geophysica (ozone, water vapor, NO, NOy, CH4 and CO)
in the altitude range up to 20 km (or up to 450 K potential temperature),
i.e. spanning the entire TTL region roughly extending
between 350 and 420 K.
Here, analysis of transport across the TTL is performed
using a new version of the
Chemical Lagrangian Model of the Stratosphere (CLaMS). In this new
version, the stratospheric model has been extended to the earth surface.
Above the tropopause, the isentropic and cross-isentropic advection in CLaMS
is driven by meteorological analysis winds
and heating/cooling rates derived from a radiation calculation.
Below the tropopause, the model smoothly transforms from the isentropic to
the hybrid-pressure coordinate and, in this way, takes into account the
effect of large-scale convective transport
as implemented in the vertical wind of the meteorological analysis.
As in previous CLaMS simulations, the irreversible transport, i.e. mixing,
is controlled by the local horizontal strain and vertical shear rates.
Stratospheric and tropospheric signatures in the TTL can
be seen both in the observations and in the model.
The composition of air above ≈350 K is mainly controlled
by mixing on a time scale of weeks or even months. Based on
CLaMS transport studies where mixing can be completely switched
off, we deduce that vertical mixing, mainly driven by the vertical shear in
the tropical flanks of the subtropical jets and, to some extent, in the
the outflow regions of the large-scale convection, offers an
explanation for the upward transport of trace species
from the main convective outflow at around 350 K up to the tropical
tropopause around 380 K.
Citation: Konopka, P., Günther, G., Müller, R., dos Santos, F. H. S., Schiller, C., Ravegnani, F., Ulanovsky, A., Schlager, H., Volk, C. M., Viciani, S., Pan, L. L., McKenna, D.-S., and Riese, M.: Contribution of mixing to upward transport across the tropical tropopause layer (TTL), Atmos. Chem. Phys., 7, 3285-3308, doi:10.5194/acp-7-3285-2007, 2007.