To text describing this figure   To MLS home page    To MLS scientific results page equivalent latitude plot of O3 change in the northern hemisphere beteween February and March of 1993
This shows the change in northern hemisphere ozone observed by MLS between 10 February and 17 March 1993, as a function of equivalent latitude and height. `Equivalent latitude' is the latititude enclosing the same amount of poleward area as a given contour of potential vorticity, and the black line indicates the approximate edge of the Arctic vortex. During this period of time ClO, the predominant form of reactive chlorine that destroys ozone, was observed by MLS to be enhanced inside the vortex (right of the black line) and below ~25 km. Transport processes tend to increase ozone in the vortex at all altitudes shown here for this period of time, and analysis of tracer data shows that the observed decrease of vortex ozone below ~25 km cannot be due to transport processes. The observed ozone decrease is consistent with depletion expected from the amount of observed ClO. The maximum decrease of ~1 ppmv (part per million by volume) corresponds to ~25% in a narrow layer. The data and analyses are discussed by Manney et al. [1994]. See also MacKenzie et al. [1996].

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