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| Titel |
Dynamics and predictability of Asian Monsoon and nonlinear dimensionality reduction |
| VerfasserIn |
Abdel Hannachi, Andy Turner |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250075671
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| Zusammenfassung |
| The Asian summer monsoon is a high dimensional and highly nonlinear phenomenon
involving considerable moisture transport into land from ocean, and is critical for
the whole region. We have used the European Reanalysis ERA-40 sea-level pressure
(SLP) anomalies, with respect to the seasonal cycle, over the region
$(50E-145E, 20S-35N)$ to study the nonlinearity of the Asian monsoon using
Isomap. We have focussed on the two-dimensional embedding of the SLP anomalies.
Unlike the unimodality obtained from the empirical orthogonal function space, the
probability density function, within the two-dimensional Isomap space, turns out
to be bimodal. A clustering procedure is applied and reveals that the data support
three clusters, which are identified using a three-component bivariate Gaussian
mixture model. The modes are found to be associated respectively with the
break and the active phases of the monsoon in addition to a third phase: the
China sea active phase. Using the low-level wind field anomalies the active phase
is found to be characterised by a strengthening and an eastward extension of the
Somali jet whereas during the break phase the Somali jet is weakened and
reversed by an easterly flow emanating from the West Pacific. The effect of
large scale seasonal mean monsoon and lower boundary forcing is also investigated
and discussed. |
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