HR: 08:45h
AN: A11D-04 INVITED     [Abstracts]
TI: Control of Stratospheric Water Vapor
AU: * Fueglistaler, S
EM: stefan@atmos.washington.edu
AF: Atmospheric Science, U. Washington, Seattle, Seattle, WA 98195 United States
AU: Bonazzola, M
EM: Marine.Bonazzola@ecmwf.int
AF: European Center for Medium-range Weather Forecast, Shinfield Park, Reading, RG29AX United Kingdom
AU: Haynes, P H
EM: P.H.Haynes@damtp.cam.ac.uk
AF: DAMTP, U. Cambridge, Wilberforce Road, Cambridge, CB30WA United Kingdom
AU: Peter, T
EM: thomas.peter@ethz.ch
AF: IAC, ETH Zuerich, Hoenggerberg, Zuerich, 8093 Switzerland
AB: We use trajectory calculations based on European Center for Medium-range Weather Forecast reanalysis data (ERA-40) to analyse tropical troposphere to stratosphere transport (TST) for the period 1979-2001. Based on the minimum saturation mixing ratio of tropical TST we calculate estimates for the humidity of air entering the stratosphere ([H2O]e). We show that this estimate, which considers the planetary scale dynamics of tropical TST and the synoptic-scale temperature field, but greatly simplifies cloud microphysics and largely neglects mesoscale temperature perturbations, yields an excellent first order estimate for the annual mean, seasonal cycle and even interannual variability of [H2O]e. Having established a tight relationship between [H2O]e and the Lagrangian mean cold point temperature in the tropics, we argue that it is the synoptic scale temperature field in combination with planetary-scale dynamics at the tropical tropopause that controls [H2O]e, and mesoscale processes such as deep, overshooting convection may play only a secondary role. Finally, we discuss the implications of this hypothesis for the cause of the observed decadal-scale positive trend of stratospheric moisture, and the apparently paradoxical negative trend of tropopause temperatures in the tropics.
DE: 3362 Stratosphere/troposphere interactions
DE: 0341 Middle atmosphere--constituent transport and chemistry (3334)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting