The role of the winter residual circulation in the summer mesopause regions in WACCM
High winter planetary wave activity warms the summer polar mesopause via a link between the two hemispheres. Complex wave–mean-flow interactions take place on a global scale, involving sharpening and weakening of the summer zonal flow. Changes in the wind shear occasionally generate flow...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-03-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/18/4217/2018/acp-18-4217-2018.pdf |
| _version_ | 1818970841397854208 |
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| author | M. S. Kuilman B. Karlsson |
| author_facet | M. S. Kuilman B. Karlsson |
| author_sort | M. S. Kuilman |
| collection | DOAJ |
| description | High winter planetary wave activity warms the summer polar mesopause via a
link between the two hemispheres. Complex wave–mean-flow interactions take place on a global scale, involving sharpening and weakening of the summer zonal flow. Changes in the wind shear occasionally generate flow instabilities. Additionally, an altering zonal wind modifies the breaking of vertically propagating gravity waves. A crucial component for changes in the summer zonal flow is the equatorial temperature, as it modifies latitudinal gradients. Since several mechanisms drive variability in the summer zonal flow, it can be hard to
distinguish which one is dominant. In the mechanism coined interhemispheric
coupling, the mesospheric zonal flow is suggested to be a key player for how
the summer polar mesosphere responds to planetary wave activity in the winter
hemisphere. We here use the Whole Atmosphere Community Climate Model (WACCM)
to investigate the role of the summer stratosphere in shaping the conditions
of the summer polar mesosphere. Using composite analyses, we show that in the
absence of an anomalous summer mesospheric temperature gradient between the
equator and the polar region, weak planetary wave forcing in the winter would
lead to a warming of the summer mesosphere region instead of a cooling, and
vice versa. This is opposing the temperature signal of the interhemispheric
coupling that takes place in the mesosphere, in which a cold and calm winter
stratosphere goes together with a cold summer mesopause. We hereby strengthen
the evidence that the variability in the summer mesopause region is mainly
driven by changes in the summer mesosphere rather than in the summer
stratosphere.</p> |
| first_indexed | 2024-12-20T14:42:53Z |
| format | Article |
| id | doaj.art-e431bb25d2fe4fe99fdb201ff192da5e |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-20T14:42:53Z |
| publishDate | 2018-03-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-e431bb25d2fe4fe99fdb201ff192da5e2022-12-21T19:37:14ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242018-03-01184217422810.5194/acp-18-4217-2018The role of the winter residual circulation in the summer mesopause regions in WACCMM. S. Kuilman0B. Karlsson1Department of Meteorology, Stockholm University, 10691 Stockholm, SwedenDepartment of Meteorology, Stockholm University, 10691 Stockholm, SwedenHigh winter planetary wave activity warms the summer polar mesopause via a link between the two hemispheres. Complex wave–mean-flow interactions take place on a global scale, involving sharpening and weakening of the summer zonal flow. Changes in the wind shear occasionally generate flow instabilities. Additionally, an altering zonal wind modifies the breaking of vertically propagating gravity waves. A crucial component for changes in the summer zonal flow is the equatorial temperature, as it modifies latitudinal gradients. Since several mechanisms drive variability in the summer zonal flow, it can be hard to distinguish which one is dominant. In the mechanism coined interhemispheric coupling, the mesospheric zonal flow is suggested to be a key player for how the summer polar mesosphere responds to planetary wave activity in the winter hemisphere. We here use the Whole Atmosphere Community Climate Model (WACCM) to investigate the role of the summer stratosphere in shaping the conditions of the summer polar mesosphere. Using composite analyses, we show that in the absence of an anomalous summer mesospheric temperature gradient between the equator and the polar region, weak planetary wave forcing in the winter would lead to a warming of the summer mesosphere region instead of a cooling, and vice versa. This is opposing the temperature signal of the interhemispheric coupling that takes place in the mesosphere, in which a cold and calm winter stratosphere goes together with a cold summer mesopause. We hereby strengthen the evidence that the variability in the summer mesopause region is mainly driven by changes in the summer mesosphere rather than in the summer stratosphere.</p>https://www.atmos-chem-phys.net/18/4217/2018/acp-18-4217-2018.pdf |
| spellingShingle | M. S. Kuilman B. Karlsson The role of the winter residual circulation in the summer mesopause regions in WACCM Atmospheric Chemistry and Physics |
| title | The role of the winter residual circulation in the summer mesopause regions in WACCM |
| title_full | The role of the winter residual circulation in the summer mesopause regions in WACCM |
| title_fullStr | The role of the winter residual circulation in the summer mesopause regions in WACCM |
| title_full_unstemmed | The role of the winter residual circulation in the summer mesopause regions in WACCM |
| title_short | The role of the winter residual circulation in the summer mesopause regions in WACCM |
| title_sort | role of the winter residual circulation in the summer mesopause regions in waccm |
| url | https://www.atmos-chem-phys.net/18/4217/2018/acp-18-4217-2018.pdf |
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