Characterizing regimes of atmospheric circulation in terms of their global superrotation
The global superrotation index S compares the integrated axial angular momentum of the atmosphere to that of a state of solid-body corotation with the underlying planet. The index S is similar to a zonal Rossby number, which suggests it may be a useful indicator of the circulation regime occupied by...
| Main Authors: | , , |
|---|---|
| Format: | Journal article |
| Language: | English |
| Published: |
American Meteorological Society
2021
|
| _version_ | 1797068218878132224 |
|---|---|
| author | Lewis, NT Colyer, GJ Read, PL |
| author_facet | Lewis, NT Colyer, GJ Read, PL |
| author_sort | Lewis, NT |
| collection | OXFORD |
| description | The global superrotation index S compares the integrated axial angular momentum of the atmosphere to that of a state of solid-body corotation with the underlying planet. The index S is similar to a zonal Rossby number, which suggests it may be a useful indicator of the circulation regime occupied by a planetary atmosphere. We investigate the utility of S for characterizing regimes of atmospheric circulation by running idealized Earthlike general circulation model experiments over a wide range of rotation rates Ω, 8ΩE to ΩE/512, where ΩE is Earth’s rotation rate, in both an axisymmetric and three-dimensional configuration. We compute S for each simulated circulation, and study the dependence of S on Ω. For all rotation rates considered, S is on the same order of magnitude in the 3D and axisymmetric experiments. For high rotation rates, S ≪ 1 and S ∝ Ω−2, while at low rotation rates S ≈ 1/2 = constant. By considering the limiting behavior of theoretical models for S, we show how the value of S and its local dependence on Ω can be related to the circulation regime occupied by a planetary atmosphere. Indices of S ≪ 1 and S ∝ Ω−2 define a regime dominated by geostrophic thermal wind balance, and S ≈ 1/2 = constant defines a regime where the dynamics are characterized by conservation of angular momentum within a planetary-scale Hadley circulation. Indices of S ≫ 1 and S ∝ Ω−2 define an additional regime dominated by cyclostrophic balance and strong equatorial superrotation that is not realized in our simulations. |
| first_indexed | 2024-03-06T22:07:33Z |
| format | Journal article |
| id | oxford-uuid:50aaef08-e242-4832-8054-16b91d6023a2 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T22:07:33Z |
| publishDate | 2021 |
| publisher | American Meteorological Society |
| record_format | dspace |
| spelling | oxford-uuid:50aaef08-e242-4832-8054-16b91d6023a22022-03-26T16:14:57ZCharacterizing regimes of atmospheric circulation in terms of their global superrotationJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:50aaef08-e242-4832-8054-16b91d6023a2EnglishSymplectic ElementsAmerican Meteorological Society2021Lewis, NTColyer, GJRead, PLThe global superrotation index S compares the integrated axial angular momentum of the atmosphere to that of a state of solid-body corotation with the underlying planet. The index S is similar to a zonal Rossby number, which suggests it may be a useful indicator of the circulation regime occupied by a planetary atmosphere. We investigate the utility of S for characterizing regimes of atmospheric circulation by running idealized Earthlike general circulation model experiments over a wide range of rotation rates Ω, 8ΩE to ΩE/512, where ΩE is Earth’s rotation rate, in both an axisymmetric and three-dimensional configuration. We compute S for each simulated circulation, and study the dependence of S on Ω. For all rotation rates considered, S is on the same order of magnitude in the 3D and axisymmetric experiments. For high rotation rates, S ≪ 1 and S ∝ Ω−2, while at low rotation rates S ≈ 1/2 = constant. By considering the limiting behavior of theoretical models for S, we show how the value of S and its local dependence on Ω can be related to the circulation regime occupied by a planetary atmosphere. Indices of S ≪ 1 and S ∝ Ω−2 define a regime dominated by geostrophic thermal wind balance, and S ≈ 1/2 = constant defines a regime where the dynamics are characterized by conservation of angular momentum within a planetary-scale Hadley circulation. Indices of S ≫ 1 and S ∝ Ω−2 define an additional regime dominated by cyclostrophic balance and strong equatorial superrotation that is not realized in our simulations. |
| spellingShingle | Lewis, NT Colyer, GJ Read, PL Characterizing regimes of atmospheric circulation in terms of their global superrotation |
| title | Characterizing regimes of atmospheric circulation in terms of their global superrotation |
| title_full | Characterizing regimes of atmospheric circulation in terms of their global superrotation |
| title_fullStr | Characterizing regimes of atmospheric circulation in terms of their global superrotation |
| title_full_unstemmed | Characterizing regimes of atmospheric circulation in terms of their global superrotation |
| title_short | Characterizing regimes of atmospheric circulation in terms of their global superrotation |
| title_sort | characterizing regimes of atmospheric circulation in terms of their global superrotation |
| work_keys_str_mv | AT lewisnt characterizingregimesofatmosphericcirculationintermsoftheirglobalsuperrotation AT colyergj characterizingregimesofatmosphericcirculationintermsoftheirglobalsuperrotation AT readpl characterizingregimesofatmosphericcirculationintermsoftheirglobalsuperrotation |