Maximum Path Height Distributions: a Measurable Quantity Independent of Mean Age and Age Distributions for Model Comparisons
Abstract
The stratospheric lifetimes of the halocarbons and nitrous oxide measured by the LACE in situ GC are dominated by simple photolysis. Between these species, 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 in going from the tropopause to 32 km. This range in lifetimes cover the dynamic time scales of stratospheric transport, making these halocarbons extremely sensitive to the altitude degree of freedom in the stratosphere and a powerful tool for studying stratospheric dynamics. 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 (≈ 100 %). A measurement of these simple 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. We will demonstrate a measured "maximum path height distribution" using LACE midlatitude data. Comparison of measured maximum path height distributions to model estimates will represent a check that would be independent from those obtained via. comparisons to mean age, and age distributions (calculated from SF6 and CO2 measurements). A short discussion of the interplay between maximum path height, time scales for transport, and the vertical resolution of models will be given to demonstrate the usefulness of the maximum path height concept. We hope to convince modelers to included maximum path height as an effective tracer for comparisons with measurements.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2001
- Bibcode:
- 2001AGUFM.A11C..10M
- Keywords:
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- 0341 Middle atmosphere: constituent transport and chemistry (3334);
- 3334 Middle atmosphere dynamics (0341;
- 0342)