The stellar occultation spectrometer GOMOS (Global Ozone Monitoring by Occultation of Stars) on ESA's Envisat satellite measures vertical profiles O<sub>3</sub>, NO<sub>2</sub> and NO<sub>3</sub> with a high long-term stability due to the self-calibrating nature of the technique. More than 6 years of GOMOS data from August 2002 to end 2008 have been analysed to study the inter-annual variation of O<sub>3</sub>, NO<sub>2</sub> and NO<sub>3</sub> in the tropics. It is shown that the QBO of the equatorial wind induces variations in the local concentration larger than 10% for O<sub>3</sub> and larger than 25% for NO<sub>2</sub>. <br><br> Quasi-Biennial Oscillation signals can be found in the evolution of the three constituents up to at least 40 km. We found that NO<sub>3</sub> is positively correlated with temperature up to 45 km in the region where it is in chemical equilibrium with O<sub>3</sub>. Our results confirm the existence of a transition from a dynamical control of O<sub>3</sub> below 28 km with O<sub>3</sub> correlated with temperature and a chemical/temperature control between 28 and 38 km with O<sub>3</sub> anti-correlated with NO<sub>2</sub> and temperature. Above 38 km and up to 50 km a different regime is found with O<sub>3</sub> and NO<sub>2</sub> correlated with each other and anti-correlated with temperature. For the NO<sub>2</sub>/temperature anti-correlation in the upper stratosphere, our proposed explanation is the modulation of the N<sub>2</sub>O ascent by the QBO up to 45 km. The oxidation of N<sub>2</sub>O is the main source of NO<sub>y</sub> in this altitude region. An enhancement of the ascending motion will cool adiabatically the atmosphere and will increase the amount of N<sub>2</sub>O concentration available for NO<sub>y</sub> formation.