WP 2: Dynamics

Leaders: N. Huret, A. Engel

The main objectives are:

All results obtained will be used to diagnose and improve transport and mixing representation in model and investigate mixing processes parameterization.

This proposal is thematically linked to the WP Dynamics (Leader N. Huret, Franck Lefevre) from ANR, IPEV,CNRS funded StraPolÉté project coordinated by N. Huret. Within StraPolÉté the summer stratosphere has been investigated using 8 balloon flights during August 2009 to investigate the dynamical processes occurring in polar region during summer. The data set obtained here will be helpful for the data interpretation of tracer measurements from StraPolÉté project because with the joint two dataset the period from February to August will be covered and we could highlight the evolution of mixing processes occurring during several seasons. Note that this part has been submitted last year and is this year enriched by the measurements planned MIPAS payload.

A. Dynamical evolution of the polar stratosphere from vortex to springtime

Questions we will try to answer

The measurements of (N2O,CH4,SF6,H2O) on the four payloads will be compared to previous measurements obtained during the last 15 years to investigate possible changes in correlations over the vortex edge from the entire data set.
A sophisticated scheme for detrending such correlations is currently being developed at University Frankfurt. As long term trends are very small for most trace gases under present atmospheric conditions, the correlations are quite insensitive to the parameterisations of the detrending scheme, allowing us to determine a quasi-steady state correlation function. This will serve as a reference to find the best detrending parameterisations for previously observed correlations, where atmospheric trends had a stronger impact.

B. Brewer-Dobson circulation

Questions we will try to answer

We will use observations of age tracers (CO2, SF6, CF4, C2F6) available from the whole air sampler and from the MIPAS-B2 data to extend the time series of high latitude mean age observations and to investigate these with respect to long term change and short term variability. The inclusion of new age tracers (CF4 and C2F6) will corroborate the results of mean age determination from the classical age tracers CO2 and SF6. As these latter age tracers are less influenced by mesospheric loss and by non-linearities in their tropospheric time series, they will provide a valuable internal validation of mean age determination.

C. Filamentation and thin dynamical structures

Questions we will try to answer

The observation of the evolution of the tracer-tracer correlations from vortex conditions to spring time will allow us to diagnose mixing across the vortex edge, characterize vortex filamentation and springtime specific dynamical structures. Note that FrIAC's very recently observed from satellite seems to be linked the QBO phase (ThiƩblemont et al., 2011, EGU conf. and JAS, in preparation) and this assumption has to be confirmed.
Tracer measurements of each the four payload (CH4, N2O, H2O, O3, CO) will be used to evaluate the ability of the CLaMS and MIMOSA Model to represent the dynamical evolution of the stratosphere from vortex conditions to spring time.

Link to the description of the other workpackages.