Looking for evidence of changes in stratospheric circulation using measurements of halocarbons and N20
Abstract
The stratospheric lifetimes of the halocarbons and nitrous oxide are dominated by simple photolysis. For this class of trace gases measured by our airborne GC, local lifetimes span two orders of magnitude at any given altitude. Similarly, for each species the local photolytic lifetimes decrease by more than two orders of magnitude from the tropopause to 32 km. This range in lifetimes covers the dynamic time scales of stratospheric transport, and makes these halocarbons extremely sensitive to the altitude degree of freedom in the stratospheric transport. Tagging an irreducible air parcel (air particle) in terms of the maximum height encountered during its path to a final location takes advantage of this logarithmic decrease with altitude in the local photolytic lifetimes. In particular, maximum path height identifies the molecular species that will have undergone substantial loss as opposed to paths whose maximum height affords little loss. A measurement of these photolytic species at a given location in the stratosphere can then be used to calculate the distribution of maximum path heights corresponding to the distribution of irreducible air particles that make up the particular air parcel measured. Changes in the vertical profiles of these photolytic species and the path distributions generated from them are powerful tools for studying change in stratospheric dynamics with far more sensitivity to changes in the vertical path than to changes in the time scales of transport. This approach therefore complements the use of age of air to monitor changes in stratospheric circulation. We will focus on the time period before and after the observed changes in stratospheric water vapor in the year 2000.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.A21C0180M
- Keywords:
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- 0341 Middle atmosphere: constituent transport and chemistry (3334);
- 3334 Middle atmosphere dynamics (0341;
- 0342)