Response of tropical stratospheric O3, NO2 and NO3 to the equatorial Quasi-Biennial Oscillation and to temperature as seen from GOMOS/ENVISAT
The stellar occultation spectrometer GOMOS (Global Ozone Monitoring by\nOccultation of Stars) on ESA's Envisat satellite measures vertical\nprofiles O-3, NO2 and NO3 with a high long-term stability due to the\nself-calibrating nature of the technique. More than 6 years of GOMOS\ndata from August 2002 to end 2008 have been analysed to study the\ninter-annual variation of O-3, NO2 and NO3 in the tropics. It is shown\nthat the QBO of the equatorial wind induces variations in the local\nconcentration larger than 10% for O-3 and larger than 25% for NO2.\nQuasi-Biennial Oscillation signals can be found in the evolution of the\nthree constituents up to at least 40 km. We found that NO3 is positively\ncorrelated with temperature up to 45 km in the region where it is in\nchemical equilibrium with O-3. Our results confirm the existence of a\ntransition from a dynamical control of O-3 below 28 km with O-3\ncorrelated with temperature and a chemical/temperature control between\n28 and 38 km with O-3 anti-correlated with NO2 and temperature. Above 38\nkm and up to 50 km a different regime is found with O-3 and NO2\ncorrelated with each other and anti-correlated with temperature. For the\nNO2/temperature anti-correlation in the upper stratosphere, our proposed\nexplanation is the modulation of the N2O ascent by the QBO up to 45 km.\nThe oxidation of N2O is the main source of NOy in this altitude region.\nAn enhancement of the ascending motion will cool adiabatically the\natmosphere and will increase the amount of N2O concentration available\nfor NOy formation.