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5. Conclusions
In
this paper, July 1994 extratropical total ozone field is comprehensively
explored over time scales ranging from monthly to synoptic. The structure
of stationary ozone field shows a clear signature of wave number 1 at middle-to-high
latitudes with a minimum well above the climatological mean over southern
SA. This minimum seems to be related to enhanced stationary atmospheric
activity over the region, as well as to a subpolar jet maximum displaced
westward over the southern Atlantic. For middle to low latitudes (up to
25ºS) ozone stationary fluctuations are determined by "tropopause
effect".
Transient
ozone fluctuations were also analysed in relation with upper-tropospheric
wave activity. Mayor zones of standard deviation of ozone daily perturbations
are shown to coincide with the regions of maximum standard deviation of
300-hPa geopotential height perturbations, although the former usually
attain their maximum slightly poleward and downstream. In particular, southern
SA display a maximum of both ozone and geopotential height standard deviation
in association with the presence of a quasi-stationary, equivalent-barotropic
ridge centered near 55ºS, 90ºW.
During July 7th to 10th a transient ozone wave evolving along subpolar jet latitudes was modulated and maintained by atmospheric activity. In order to determine the relative dynamical contributions from atmospheric waves to ozone distribution two approaches were pursued. Firstly, ozone local daily changes were explained in terms of a simple ozone transport equation and by use of the mapping technique. This approach yielded results that although overestimate local ozone changes, were able to reproduce comparable spatial patterns. The second approach proposed a multivariate linear regression model that relates ozone content to tropopause pressure and potential vorticity on isentropic surfaces. Results suggested that these quantities are valid predictors for ozone field; the most important contribution given by the potential vorticity on 315ºK and by tropopause pressure.
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