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| Titel |
Forced and internal modes of variability of the East Asian summer monsoon |
| VerfasserIn |
J. Liu, B. Wang, J. Yang |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 4, no. 4 ; Nr. 4, no. 4 (2008-11-03), S.225-233 |
| Datensatznummer |
250001865
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| Publikation (Nr.) |
 copernicus.org/cp-4-225-2008.pdf |
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| Zusammenfassung |
The modern instrumental record (1979–2006) is analyzed in an attempt to
reveal the dynamical structure and origins of the major modes of interannual
variability of East Asian summer monsoon (EASM) and to elucidate their
fundamental differences with the major modes of seasonal variability. These
differences are instrumental in understanding of the forced (say orbital)
and internal (say interannual) modes of variability in EASM. We show that
the leading mode of interannual variation, which accounts for about 39%
of the total variance, is primarily associated with decaying phases of major
El Nino, whereas the second mode, which accounts for 11.3% of the total
variance, is associated with the developing phase of El Nino/La Nina. The
EASM responds to ENSO in a nonlinear fashion with regard to the developing
and decay phases of El Nino. The two modes are determined by El Nino/La Nina
forcing and monsoon-warm ocean interaction, or essentially driven by
internal feedback processes within the coupled climate system. For this
internal mode, the intertropical convergence zone (ITCZ) and subtropical
EASM precipitations exhibit an out-of-phase variations; further, the Meiyu
in Yangtze River Valley is also out-of-phase with the precipitation in the
central North China.
In contrast, the annual cycle forced by the solar radiation shows an
in-phase variation between the ITCZ and the subtropical EASM precipitation.
Further, the seasonal march of precipitation displays a continental-scale
northward advance of a southwest-northeastward tilted rainband from mid-May
toward the end of July. This coherent seasonal advance between Indian and
East Asian monsoons suggests that the position of the northern edge of the
summer monsoon over the central North China may be an adequate measure of
the monsoon intensity for the forced mode. Given the fact that the annual
modes share the similar external forcing with orbital variability, the
difference between the annual cycle and interannual variation may help to
understand the differences in the EASM variability on the orbital time scale
and in the modern records. |
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