Atmospheric Chemistry and Physics, vol. 10, issue 18 (2010) pp. 8873-8879
The stellar occultation spectrometer GOMOS (Global Ozone Monitoring by
Occultation of Stars) on ESA's Envisat satellite measures vertical
profiles O-3, NO2 and NO3 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-3, NO2 and NO3 in the tropics. It is shown
that the QBO of the equatorial wind induces variations in the local
concentration larger than 10% for O-3 and larger than 25% for NO2.
Quasi-Biennial Oscillation signals can be found in the evolution of the
three constituents up to at least 40 km. We found that NO3 is positively
correlated with temperature up to 45 km in the region where it is in
chemical equilibrium with O-3. Our results confirm the existence of a
transition from a dynamical control of O-3 below 28 km with O-3
correlated with temperature and a chemical/temperature control between
28 and 38 km with O-3 anti-correlated with NO2 and temperature. Above 38
km and up to 50 km a different regime is found with O-3 and NO2
correlated with each other and anti-correlated with temperature. For the
NO2/temperature anti-correlation in the upper stratosphere, our proposed
explanation is the modulation of the N2O ascent by the QBO up to 45 km.
The oxidation of N2O is the main source of NOy in this altitude region.
An enhancement of the ascending motion will cool adiabatically the
atmosphere and will increase the amount of N2O concentration available
for NOy formation.
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