Etude des tendances d'ozone et de dioxyde d'azote dans la stratosphère tropicale

Maud Pastel 1
1 STRATO - LATMOS
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
Abstract : The tropical region is the main entry point of the chemical species in the troposphere lifted into the stratosphere. They are then redistributed to higher latitudes via the Brewer Dobson. Thus any change of stratospheric constituents in the tropics will have an impact on their distribution at mid latitudes. Long series of O3 and NO2 columns in the tropics are available from 2 SAOZ stations (UV-Vis spectrometers): at Bauru (22°S-49°W) since 1995 and in La Réunion (21°S-55°E) since 1993. The most significant modulation for both components is the seasonal cycle (40%). A multiple regression analysis of O3 and NO2 columns at Bauru and La Reunion has quantified the impact of solar and geophysical parameters on their variability. Following this analysis, the cycles of the most influential parameters are, in decreasing order: the Quasi-Biennal Oscillation with 40% for both species, the El-Niño Southern Oscillation with 25% for O3 and 20% for NO2, the solar flux with 15 and 18%, and the aerosols with 20 and 12%. After subtracting these influences, the residual variations of O3 are not significant. Those of NO2 indicate an increase from 2001 to 2006, followed by a decrease in 2007. From variations of the Eddy heat flux, variations in average intensity of meridional exchange through the southern subtropical barrier have been identified since 2001. These distortions have been detected through the modulation of the 2 tropical stations equivalent latitude. Taking into account these changes yields to an increase in the concentration of NO2 in the tropics (3%/dec) consistent with the one estimated of N2O (2.5%/dec), the gas source of nitrogen oxides in the stratosphere
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Maud Pastel. Etude des tendances d'ozone et de dioxyde d'azote dans la stratosphère tropicale. Océan, Atmosphère. Université Pierre et Marie Curie - Paris VI, 2011. Français. ⟨tel-00734917⟩

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