Middle stratospheric polar vortex ozone budget during the warming Arctic winter, 2002–2003

The ozone budget inside the middle stratospheric polar vortex (24–36 km) during the 2002–2003 Arctic winter is studied by analyzing Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) satellite data. A comprehensive global chemical transport model (Model for Ozone and Related Chemical Tracers, MOZART-3) is used to analyze the observed variation in polar vortex ozone during the stratospheric sudden warming (SSW) events. Both MIPAS measurement and MOZART-3 calculation show that a pronounced increase (26–28 DU) in the polar vortex ozone due to the SSW events. Due to the weakening of the polar vortex, the exchange of ozone mass across the edge of the polar vortex increases substantially and amounts to about 3.0×107 kg according to MOZART-3 calculation. The enhanced downward transport offsets about 80% of polar vortex ozone mass increase by horizontal transport. A “passive ozone” experiment shows that only ∼55% of the vertical ozone mass flux in February and March can be attributed to the variation in vertical transport. It is also shown that the enhanced downward ozone above ∼32 km should be attributed to the springtime photochemical ozone production. Due to the increase of air temperature, the NOx reaction rate increases by 40%–80% during the SSW events. As a result, NOx catalytic cycle causes another 44% decrease in polar vortex ozone compared to the net ozone changes due to dynamical transport. It is also shown that the largest change in polar vortex ozone is due to horizontal advection by planetary waves in January 2003.