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| Titel |
A new mechanism for ocean-atmophere coupling in midlatitudes |
| VerfasserIn |
Arnaud Czaja, Nicholas Blunt |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250048113
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| Zusammenfassung |
| The role of moist convection in “transferring” upward surface ocean conditions throughout
the troposphere is studied in reanalysis data for the Northern and Southern extra-tropical
Hemispheres in winter. It is found that conditions for the development of a convective air
column from the sea surface to the tropopause are met frequently over all major
western boundary currents and their extension in the oceanic interior (sometimes
by as much as 50% of the time). These large occurences are shown to be jointly
controlled by oceanic advection of warm waters and, on the atmospheric side, by
the downward displacement of the tropopause associated with synoptic weather
systems.
Based on these results, it is proposed that the oceans can influence the atmosphere
directly through convection in midlatitudes, as is commonly thought to occur in the Tropics.
Analysis of the Richardson number Ri found at low levels suggest that moist symmetric
instability (0 < Ri -¤ 1) is a key process involved in linking surface ocean temperatures to
atmospheric lapse-rates, in addition to standard upright convection. These low Ri processes
are not currently parameterized in climate models, which raises the possibility that the
extra-tropical oceanic influence on climate might be underestimated in the current generation
of models. |
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