 |
| Titel |
Representation of the Antarctic Oscillation and related precipitation in the MPI Earth System Model |
| VerfasserIn |
Stella Babian, Henning W. Rust, Jens Grieger, Ulrich Cubasch |
| Konferenz |
EGU General Assembly 2015
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250112475
|
| Publikation (Nr.) |
 EGU/EGU2015-12635.pdf |
|
|
|
|
|
| Zusammenfassung |
| The Antarctic Oscillation (AAO) is the dominant mode of atmospheric
variability on the southern hemisphere. It is obtained via a principal
component analysis (PCA) for geopotential height anomalies. In this
study the 700hPa geopotential field are used to comply with the NOAAs
definition of the AAO. Being the southern hemisphere's dominant mode, an
adequate representation in earth system models is desirable.
This study evaluates to what extend the AAO and related precipitation
is represented in the Max Planck Institute's earth system model
(MPI-ESM). To this end the AAO spatial patterns (Empirical Orthogonal
Functions, EOFs), spectral properties of the associated principal
components (PCs) and AAO-related precipitation of MPI-ESM are compared
to three reanalyses: the ECMWF's ERA-40 and ERA-Interim, and the
NCEP/NCAR 40-year reanalysis project. Differences between MPI-ESM and
ERA-Interim leading EOFs reveal that the three typical centres of
action are less pronounced and slightly shifted in the model.
Spectral density estimates of the associated PCs show reduced
variability in the MPI-ESM for periods between 4 to 5 months.
The relation between AAO and southern hemispheric precipitation is
assessed via composites and correlation analysis. In both, model and
reanalyses, a negative AAO index leads to a general increase of
precipitation between 30°S and 50°S and a decrease south of 50°S.
Differences between correlation maps are most prominent near Indonesia
and Antarctica. In summary, the MPI-ESM underestimates the relation of
AAO and southern hemispheric precipitation but gives the correct sign
and spatial distribution of correlation values. |
|
|
|
|
|
|