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| Titel |
The impact of extratropical warming on the tropical precipitation |
| VerfasserIn |
Masakazu Yoshimori, Ayako Abe-Ouchi, Hiroaki Tatebe, Toru Nozawa |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250147172
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| Publikation (Nr.) |
 EGU/EGU2017-11290.pdf |
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| Zusammenfassung |
| From paleoclimate evidence to future climate projections, it has been reported that the
asymmetric warming (or cooling) between the northern and southern hemisphere extratropics
induces the meridional shift in the tropical precipitation. Such a shift is often understood by
the energy-flux framework in that the extra energy is transported from more warming to
less warming hemispheres through the change in the Hadley circulation. As the
Hadley circulation transports energy in opposite direction to the moisture, the tropical
precipitation tends to be intensified in the hemisphere of a larger warming. This framework
is shown to be particularly useful for modelling results without ocean dynamical
feedback. In the current study, a fully coupled atmosphere-ocean model is used to
investigate the impact of extratropical warming on the tropical precipitation under the
realistic RCP4.5 scenario. It is shown that the mid-high latitude warming alone in
the poleward of 40∘ (56% global warming) can significantly affect the tropical
precipitation change in the equatorward of 20∘ (38% hemispheric contrast) from
late autumn to early winter. High-latitude warming alone affects much less. This
meridional change in the tropical precipitation is largely explained by the circulation
change, rather than the humidity change. The reduced northward eddy momentum and
heat fluxes in the northern hemisphere induces anomalous Hadley circulation in
the northern tropics. This change seems to weaken the equatorial upwelling in the
Pacific, which leads to the equatorial SST rise. The equatorial sea surface warming
induces the meridionally symmetric pattern of the anomalous Hadley circulation
(though, asymmetric in strength), resulting in the northward migration of the tropical
precipitation. The larger change in the ocean heat transport near the equator, relative to the
atmosphere, requires a more refined theory than the conventional energy-flux framework. |
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