Insight from ozone and water vapour on transport in the tropical tropopause layer (TTL) 1Institute for Chemistry and Dynamics of the Geosphere (ICG-1), Forschungszentrum Jülich, Jülich, Germany
14 Jan 2011
2Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, UK
3CAO, Dolgoprudny, Russia
4Institute of Atmospheric Sciences and Climate, ISAC-CNR, Bologna, Italy
5Dept. of Geosciences, Princeton University, Princeton, NJ, USA
Received: 25 Aug 2010 – Published in Atmos. Chem. Phys. Discuss.: 01 Oct 2010 Abstract. We explore the potential of ozone observations to constrain transport processes
in the tropical tropopause layer (TTL), and contrast it with insights
that can be obtained from water vapour.
Global fields from Halogen Occultation Experiment (HALOE)
and in-situ observations are predicted
using a backtrajectory approach that captures advection,
instantaneous freeze-drying and photolytical ozone production.
Two different representations of transport (kinematic and diabatic 3-month
backtrajectories based on ERA-Interim data) are used to evaluate the sensitivity to differences in transport.
Results show that mean profiles and seasonality of both tracers can be
reasonably reconstructed. Water vapour predictions are similar
for both transport representations, but predictions for
ozone are systematically higher for kinematic transport.
Compared to global HALOE observations, the diabatic model prediction
underestimates the vertical ozone gradient. Comparison of the kinematic
prediction with observations obtained during the tropical SCOUT-O3 campaign
shows a large high bias above 390 K potential temperature.
We show that ozone predictions and vertical dispersion of the trajectories
are highly correlated, rendering ozone an interesting tracer
for aspects of transport to which water vapour is not sensitive.
We show that dispersion and mean upwelling have similar
effects on ozone profiles, with slower upwelling
and larger dispersion both leading to higher ozone concentrations.
Analyses of tropical upwelling based on mean transport
characteristics, and model validation
have to take into account this ambiguity
between tropical ozone production and in-mixing from the stratosphere.
In turn, ozone provides constraints on transport in the TTL and
lower stratosphere that cannot be obtained from water vapour.
Revised: 22 Dec 2010 – Accepted: 05 Jan 2011 – Published: 14 Jan 2011
Citation: Ploeger, F., Fueglistaler, S., Grooß, J.-U., Günther, G., Konopka, P., Liu, Y.S., Müller, R., Ravegnani, F., Schiller, C., Ulanovski, A., and Riese, M.: Insight from ozone and water vapour on transport in the tropical tropopause layer (TTL), Atmos. Chem. Phys., 11, 407-419, doi:10.5194/acp-11-407-2011, 2011.