Séminaire LATMOS à Guyancourt (amphithéâtre Gérard Mégie) le 27 Mars à 11h

Orateur: Federico Fierli (ISAC-CNR, Bologne)

Titre: "Variability and trend of the stratospheric subtropical barrier"


Résumé: We analyse the average structure and the variability of the stratospheric dynamical barrier located in the subtropics. For this we use Probability Density Functions (PDFs) of the long-lived tracers

nitrous oxide (N2O) and methane (CH4) from different satellite instruments: the Microwave Limb Sounder (MLS) on board Aura, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS)

on board Envisat, the Sub-Millimetre Radiometre (SMR) on board Odin and the Halogen Occultation Experiment (HALOE) on board UARS, overall covering the time period of 1992–2009. In addition we

apply the same analysis to CCMVAL model data for the same set of tracers and within a compatible time window. We present the analysis of the consistency among the different datasets and their capability

of identifying mixing regions and barrier-to-transport regions in the stratosphere and the subtropical barrier location. There is a strong seasonality consistently represented by observations and models,

characterized by the wintertime shift of the subtropical edge toward the summer hemisphere; in addition the barrier position is modulated by the QBO, due to the role of planetary waves breaking and

residual circulation. We conclude our analysis evaluating possible trends in the barrier morphology and position at decadal timescale.