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| Titel |
Monsoon convection dynamics and nonlinear dimensionality reduction vis Isomap |
| VerfasserIn |
A. Hannachi, A. Turner |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250066279
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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 computed within the two-dimensional Isomap space is
shown 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.
Two modes are associated with an active phase over India/Bay of Bengal
and East China sea respectively, whereas the third mode is associated
witha break over East/South China sea. Using the low-level wind field
anomalies the (first mode) active phase is
found to be characterised by a strengthening and an eastward extension
of the Somali jet whereas during the (second mode) 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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