 |
| Titel |
Seasonal predictions of equatorial Atlantic SST in a low-resolution CGCM with surface heat flux correction |
| VerfasserIn |
Tina Dippe, Richard Greatbatch, Hui Ding |
| Konferenz |
EGU General Assembly 2016
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250128192
|
| Publikation (Nr.) |
 EGU/EGU2016-8151.pdf |
|
|
|
|
|
| Zusammenfassung |
| The dominant mode of interannual variability in tropical Atlantic sea surface temperatures
(SSTs) is the Atlantic Niño or Zonal Mode. Akin to the El Niño-Southern Oscillation in the
Pacific sector, it is able to impact the climate both of the adjacent equatorial African
continent and remote regions. Due to heavy biases in the mean state climate of the
equatorial-to-subtropical Atlantic, however, most state-of-the-art coupled global
climate models (CGCMs) are unable to realistically simulate equatorial Atlantic
variability.
In this study, the Kiel Climate Model (KCM) is used to investigate the impact of a simple
bias alleviation technique on the predictability of equatorial Atlantic SSTs. Two sets of
seasonal forecasting experiments are performed: An experiment using the standard KCM
(STD), and an experiment with additional surface heat flux correction (FLX) that efficiently
removes the SST bias from simulations. Initial conditions for both experiments are generated
by the KCM run in partially coupled mode, a simple assimilation technique that forces the
KCM with observed wind stress anomalies and preserves SST as a fully prognostic
variable. Seasonal predictions for both sets of experiments are run four times yearly for
1981-2012.
Results: Heat flux correction substantially improves the simulated variability in the
initialization runs for boreal summer and fall (June-October). In boreal spring (March-May),
however, neither the initialization runs of the STD or FLX-experiments are able to capture the
observed variability.
FLX-predictions show no consistent enhancement of skill relative to the predictions of the
STD experiment over the course of the year. The skill of persistence forecasts is hardly beat
by either of the two experiments in any season, limiting the usefulness of the few forecasts
that show significant skill. However, FLX-forecasts initialized in May recover skill in July
and August, the peak season of the Atlantic Niño (anomaly correlation coefficients of about
0.3). Further study is necessary to determine the mechanism that drives this potentially useful
recovery. |
|
|
|
|
|
|