Dynamical and chemical influences on the ozone layer
The EU project CANDIDOZ and the German BMBF project AFO2000-DYCHO focus on the different chemical and dynamical processes that determine the global ozone distribution. While the chemical change was investigated quite thoroughly in the last 20 years, the transport of ozone by the residual circulation has just recently been put into perspective as an important contributor to the year-to-year variability in ozone columns and profiles at all latitudes (Fusco and Salby, 1999, Randel et al., 2002).
Transport of ozone by the residual circulation is the dominant source of ozone at mid to high latitudes. Interannual variability in the residual circulation contributes significantly to the interannual variability in the ozone column at these latitudes. In addition to the direct dynamical effect, the residual circulation is closely connected to high-latitude stratospheric temperatures, which influence ozone chemistry. The circulation is driven by tropospheric waves propagating into the stratosphere, which can be characterized by the integrated Eliassen-Palm flux entering the stratosphere as a proxy.
Figure 1: Interannual variation of the observed late winter (late March or time of vortex breakdown, whatever came earlier) total ozone column in the geographical region covered by the polar vortex (black), the dynamical supply of ozone to the polar vortex over the winter (blue), and the chemical loss of ozone over the winter (red). The range of the ozone column observations in October each year are marked by the grey shaded area. The range of variability of these quantities over the last decade is given on the right hand side.
Figure 2: Correlation between the winter upward EP flux through 100 hPa and the change of the total ozone column during winter (black), the dynamical supply of ozone (blue), and the chemical loss of ozone (red). The total change is based on about 2000 ozonesonde observations within the Arctic polar vortices since 1992.