Isomap nonlinear dimensionality reduction and bimodality of Asian monsoon convection

Hannachi, A. and Turner, A. G. ORCID: https://orcid.org/0000-0002-0642-6876 (2013) Isomap nonlinear dimensionality reduction and bimodality of Asian monsoon convection. Geophysical Research Letters, 40 (8). pp. 1653-1658. ISSN 1944-8007 doi: 10.1002/grl.50351

Abstract/Summary

It is known that the empirical orthogonal function method is unable to detect possible nonlinear structure in climate data. Here, isometric feature mapping (Isomap), as a tool for nonlinear dimensionality reduction, is applied to 1958–2001 ERA-40 sea-level pressure anomalies to study nonlinearity of the Asian summer monsoon intraseasonal variability. Using the leading two Isomap time series, the probability density function is shown to be bimodal. A two-dimensional bivariate Gaussian mixture model is then applied to identify the monsoon phases, the obtained regimes representing enhanced and suppressed phases, respectively. The relationship with the large-scale seasonal mean monsoon indicates that the frequency of monsoon regime occurrence is significantly perturbed in agreement with conceptual ideas, with preference for enhanced convection on intraseasonal time scales during large-scale strong monsoons. Trend analysis suggests a shift in concentration of monsoon convection, with less emphasis on South Asia and more on the East China Sea.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/31508
Identification Number/DOI	10.1002/grl.50351
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > NCAS
Publisher	American Geophysical Union
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