Theory of Trace Gas Distributions in the Lower Stratosphere and Near the Tropopause

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The aim of this research is to advance the theory of trace gas transport and trace gas distributions on the global scale, and of tracer-tracer relationships. Existing theory has been quite successful in describing global trace distributions in the stratosphere and in explaining the observed different tracer-tracer relationships in the partly isolated regions of the tropical and midlatitutde stratosphere and the wintertime polar vortex. Yet existing theory has not been sufficiently well developed to exploit the full information content of these remarkably compact and reproducible relationships and, moreover, the theory fails near the tropopause where large vertical gradients of trace gas mixing ratios render some of the underlying assumptions invalid. To address these issues, theoretical development is conducted in concert with modeling of trace gas transport, the model results both guiding the theoretical development and providing tests of theoretical predictions. The four main tasks are: (1) modification of existing theory to render the theory valid near and through the tropopause, (2) investigation of factors controlling the location and shape of the tropopause as defined by trace gases, (3) clarification of the relationship between gross global trace gas fluxes and the shape of tracer-tracer relationships, and (4) analysis of non-compactness in tracer relationships.Broader impacts center on training of young scientists in this type of scientific activity. This training involves a postdoctoral scholar through direct involvement in the work; graduate students taking the principal investigator's regular course on stratospheric meteorology and transport, which will incorporate the latest results of the work; and undergraduates who are offered the opportunity to involve in components of the work through MIT's Undergraduate Research Opportunities Program.