MASS Seminar - Peter Haynes (University of Cambridge)
Date Time Location
December 11th, 2012 12:00pm-1:00pm 54-915
Lagrangian studies of tropical troposphere-to-stratosphere transport

Abstract

Troposphere-to-stratosphere transport (TST) in the tropics is governed in part by rapid convective transport within the troposphere and in part by large-scale quasi-horizontal transport in the 'tropical tropopause layer'. TST plays a major role in determining the stratospheric concentrations of important chemical species, including so-called 'Very Short-Lived Species' (VSLS) which may potentially deplete stratospheric ozone and where
stratospheric concentrations depend on the timescales for transport from the surface to the stratosphere, and water vapour, where stratospheric concentrations are determined by the temperatures encountered by air parcels as they move from troposphere to stratosphere. This talk will describe the application of Lagrangian techniques to study both these cases. For VSLS a Lagrangian technique can be used to calculate geographically and seasonally varying ozone depletion potentials (ODPs) (Pisso et al 2010). For water vapour Lagrangian calculations such as those of Fueglistaler et al (2005) showed that provided the sampling of the space and time variations of the large-scale temperature field were taken into account there was good agreement between predicted and observed water vapour concentrations. More
recently (Liu et al, 2010) the Lagrangian calculations have been refined to use trajectories based on improved meteorological analyses, in some cases using diabatic heating information to calculate vertical velocity. These calculations seem to predict water vapour concentrations that are anomalously low. Careful analysis, reported in Liu et al(2010), establishes that the anomaly is significant relative to the uncertainty in the calculation and therefore makes it worthwhile to consider what extra physics might be added to the A-C paradigm to increase predicted water vapour concentrations to bring them closer to those observed.


Fueglistaler, S., Bonazzola, M., Haynes, P.H., Peter, T., 2005:
Stratospheric water vapor predicted from the Lagrangian
temperature history of air entering the stratosphere in the
tropics J. Geophys. Res., 110, D10, D10S16,
doi:10.1029/2004JD005516.

Liu, Y.-L., Fueglistaler, S.,
Haynes, P. H., 2010: The advection-condensation paradigm
for stratospheric water vapour, J. Geophys. Res., 115,
D24307, doi:10.1029/2010JD014352.

Pisso, I., Haynes, P. H., Law, K. S. 2010: Emission location dependent ozone depletion
potentials for very short-lived halogenated species. Atmos. Chem. Phys., 10, 12025-12036.

Speaker's website : http://www.damtp.cam.ac.uk/user/phh/