 |
| Titel |
Effect of North Atlantic sea-surface temperature biases on the simulated atmospheric response |
| VerfasserIn |
Nora Specht, Jürgen Bader |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250151184
|
| Publikation (Nr.) |
 EGU/EGU2017-15741.pdf |
|
|
|
|
|
| Zusammenfassung |
| Like many state-of-the-art coupled ocean-atmosphere models, the Earth System Model
(ESM) of the Max Planck Institute for Meteorology (MPI-M) simulates strong sea surface
temperature (SST) biases in the extra-tropical North Atlantic region. A series of
SST-sensitivity experiments are performed with the corresponding atmospheric model
component ECHAM6 to investigate the effect of the North Atlantic SST biases on the
atmospheric response in particular on precipitation, storminess and atmospheric circulation.
The atmosphere-only model ECHAM6 was forced by a seasonally varying climatology of
observed global SSTs. Through the superposition of a varying extra-tropical North Atlantic
bias pattern extracted from the MPI-M ESM on top of the control field, the relevance of the
seasonal variation of extra-tropical North Atlantic biases for the simulated response is
analysed.
Results show that the SST biases have a substantial effect on the pressure distribution in
the North Atlantic region in all season. Anomalous warmer SSTs are associated with an
increase in the geopotential height and vice versa. The resulting large-scale pressure gradient
modification induces a significant southward shift of the zonal wind system including the jet.
To first order the precipitation change follows the SST bias pattern. An analysis of the
thermodynamic and dynamic mechanisms for the changes in the hydrological cycle shows
that the dynamic components modify the precipitation response not only locally over the
SST bias region, but even have a significant effect on the American and European
continents. The SST bias pattern has a substantial effect on the Eady growth rate
leading to a reduction of the storminess mainly in the northern part of the North
Atlantic. |
|
|
|
|
|
|