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A method for estimating global subgrid-scale gravity-wave temperature perturbations in chemistry-climate models
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  • Michael Weimer,
  • Catherine Wilka,
  • Douglas Edward Kinnison,
  • Rolando R. Garcia,
  • Julio T. Bacmeister,
  • M. Joan Alexander,
  • Andreas Dörnbrack,
  • Susan Solomon
Michael Weimer
Massachusetts Institute of Technology

Corresponding Author:[email protected]

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Catherine Wilka
Massachusetts Institute of Technology
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Douglas Edward Kinnison
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Rolando R. Garcia
National Center for Atmospheric Research (NCAR)
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Julio T. Bacmeister
National Center for Atmospheric Research (UCAR)
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M. Joan Alexander
NorthWest Research Associates, CoRA Office
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Andreas Dörnbrack
DLR, Institut für Physik der Atmosphäre
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Susan Solomon
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Many chemical processes depend non-linearly on temperature.
Gravity-wave-induced temperature perturbations have been previously shown to affect atmospheric chemistry, but accounting for this process in chemistry-climate models has been a challenge because many gravity waves have scales smaller than the typical model resolution.
Here, we present a method to account for subgrid-scale orographic gravity-wave-induced temperature perturbations on the global scale for the Whole Atmosphere Community Climate Model (WACCM).
The method consists of deriving the temperature perturbation amplitude $\hat{T}$ consistent with the model’s subgrid-scale gravity wave parametrization, and imposing $\hat{T}$ as a sinusiodal temperature perturbation in the model’s chemistry solver.
Because of limitations in the gravity wave parameterization, scaling factors may be necessary to maintain a realistic wave amplitude.
We explore scaling factors between 0.6 and 1 based on comparisons to altitude-dependent $\hat{T}$ distributions in two observational datasets.
We probe the impact on the chemistry from the grid-point to global scales, and show that the parametrization is able to represent mountain wave events as reported by previous literature.
The gravity waves for example lead to increased surface area densities of stratospheric aerosols.
This in turn increases chlorine activation, with impacts on the associated chemical composition.
We obtain large local changes in some chemical species (e.g., active chlorine, NOx, N2O5) which are likely to be important for comparisons to airborne or satellite observations, but find that the changes to ozone loss are more modest.
This approach enables the chemistry-climate modeling community to account for subgrid-scale gravity wave temperature perturbations in a consistent way.