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Title: Atmospheric Chemistry Signatures of an Equatorially Symmetric Matsuno–Gill Circulation Pattern
Abstract Matsuno–Gill circulations have been widely studied in tropical meteorology, but their impact on stratospheric chemistry has seldom been explicitly evaluated. This study demonstrates that, in a model nudged to reanalysis, anticyclonic Rossby wave gyres that form near the tropopause as a result of equatorially symmetric heating in the troposphere provide a dynamical mechanism to influence tropical and subtropical atmospheric chemistry during near-equinox months. The anticyclonic flow entrains extratropical air from higher latitudes into the deep tropics of both hemispheres and induces cooling in the already cold upper-troposphere/lower-stratosphere (UTLS) region. Both of these aspects of the circulation allow heterogeneous chlorine activation on sulfuric acid aerosols to proceed rapidly, primarily via the HCl + ClONO 2 reaction. Precipitation rates and heating rates from reanalysis are shown to be consistent with these heating and circulation response patterns in the months of interest. This study analyzes specified dynamics simulations from the Whole Atmosphere Community Climate Model (SD-WACCM) with and without tropical heterogeneous chemistry to demonstrate that these circulations influence substantially the distributions of, for example, NO 2 and ClO in the UTLS tropics and subtropics of both hemispheres. This provides a previously unrecognized dynamical influence on the spatial structures of atmospheric composition changes more » in the UTLS during near-equinox months. « less
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Publication Date:
Journal Name:
Journal of the Atmospheric Sciences
Page Range or eLocation-ID:
107 to 116
Sponsoring Org:
National Science Foundation
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