Name of proposer: 
Bernard Legras

Institution:
Laboratoire de Meteorologie Dynamique
Ecole Normale Superieure
24 rue Lhomond
F-75231 PARIS Cedex 05

Contact:
phone: +33-1-44-32-22-28; fax: +33-1-43-36-83-92
email: legras@lmd.ens.fr
www:   http://gershwin.ens.fr/legras

Title of contribution:
"Vertical diffusivity from Lagrangian reconstructions of ozone profiles"

Main elements:
(a) Random back-trajectories and reconstruction of tracer 
distribution along observed profiles and transects;
(b) Statistical properties of tracers in the tropopause region;
(c) Evaluation of turbulent diffusion. Test of physical hypothesis and
parameterizations used in climate models;
(d) Spatial and temporal variability of turbulent diffusion;


Relationship to MoU Objectives:
This work contributes directly to objectives 3, 4 and 5 by using gathered
data to improve our understanding of the dynamical processes in the 
tropopause region and improving our ability to modelize these processes.
It will improve assimilation through the dependance of assimilation on
the diffusive parameterization in the assimilating models. 

Relationship to scientific program:
The contributions are mainly related to part C-3 "Understanding" of
the scientific program.

Deliverables:
Main elements (a) to (d) above will produce scientific papers. Main
element (c) and (d) will produce results available to improve the diffusive 
parameterization in numerical models.


Indicative timetable:
Element (a) is already available for balloon profiles or airborne transects
(MOZAIC or research aircraft carrying ozone or methane sensors).
(c) will be conducted in 2003 on a selected number of cases. 
(b) and (d) will be done in 2004 through a systematic exploitation
of the available datasets. This work will be the core of a starting
doctoral thesis.

Manpower:
One doctoral student and the proposer himself will work on these subjects.

Assurance of availability of resources:
At the moment the work is funded through basic funding of CNRS and is also
for the investigation of tropical region part of the EU project Hibiscus.

Foreseen collaboration:
Other participants, in particular those producing tarcer in-situ measurements 
and ECMWF.

Previous experience:

The proposer has 25 years of experience in turbulence and geophysical fluid
dynamics. Recent relevant work includes

Joseph and Legras, 2002, Relation between kinematic boundaries, stirring,
and barriers for the antarctic polar vortex, J. Atmos. Sci., 59, pp. 1198-1212.

Koh and Legras, 2002, Hyperbolic lines and the stratospheric polar vortex, Chaos, 
12, pp. 382-394

Legras, Joseph and Lefevre, Vertical diffusivity in the lower
stratosphere from Lagrangian back-trajectory reconstructions of ozone
profiles, submitted to J. Geophys. Res.