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| Titel |
Aerosol-induced Changes in Boreal Winter Extratropical Circulation |
| VerfasserIn |
Yi Ming, V. Ramaswamy |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250033412
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| Zusammenfassung |
| We examine some key aspects of the boreal winter extratropical
circulation changes in response to aerosols, simulated with a
coupled atmosphere-slab ocean general circulation model. The
zonal-mean response features a pronounced equatorward shift of the
North Hemisphere subtropical jet owing to the mid-latitude aerosol
cooling. The circulation changes are also characteristic of strong
zonal asymmetry. In particular, the cooling is more concentrated
over North Pacific than over North Atlantic in spite of similar
forcings. With the help of an idealized model, we show that the
zonally asymmetric response is tightly linked to the stationary
Rossby waves excited by the anomalous diabatic heating over Tropical
Indian Ocean and West Pacific. The wave pattern leads to a
southeastward shift of the Aleutian low (and associated changes in
winds and precipitation), while leaving the Atlantic circulation
relatively unchanged.
Despite the rich circulation changes, the change in the
extratropical meridional latent heat transport is controlled
strongly by the dependence of tropospheric water vapor on
temperature, as in the global warming case. An important implication
of this finding is that one can understand/predict reliably the
variations in zonal-mean extratropical precipitation solely from
global-mean temperature change, even without a highly confident
knowledge of the detailed circulation changes caused by aerosols. On
the other hand, such a knowledge is indispensable for understanding
zonally asymmetric (regional) precipitation change. Finally, we
offer an explanation of the nonlinearity in the low and mid-latitude
temperature response based on a baroclinic instability view of the
Hadley circulation. |
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