TC ISO Coupling

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TC - ISO Coupling in the Western North
Pacific Huang-Hsiung Hsu, An-Kai Lo and Y.-L.
Chen Department of Atmospheric Sciences National
Taiwan University
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Interaction between ISO and TC
clustering effect
TC
ISO
TC
e.g., Nakazawa (1986), Heta (1992), Hartmann et
al. (1992), Liebmann et al. (1994), ,
Maloney and Dickinson (2003), Hsu and
Chen (2005),
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Strong ISO-TC Coupling in 2004 Typhoon
Season H.-H. Hsu and Y.-L. Chen (2005)

• recruving tracks - 10 typhoon landfalls in Japan
• appearing in clusters

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monsoon trough index MSLP (10N-20N, 120E-150E)
Largest variance in 1951-2004
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32-76-day variance and percentile in 2004
MSLP
OLR
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2004 JJASO
MSLP 120E-150E
MSLP 10N-20N
OLR 0-10N
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Interaction between ISO and TC
clustering effect
TC
ISO
TC
?
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Kurihara(1995) Approach used in TC initialization
Global field
Smoothing operator
Basic field
Disturbance field
Filter domain
Non-TC component
TC component
Environment flow
Specified vortex
What we need !!
Initial field
Wu et al. (2002)
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Total
Basic
Typhoon
Environment
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Remove tropical cyclones from ERA40 850 hPa
vorticity field (JJASO 1992-2001)
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10-year mean 850 hPa vorticity
Before
After
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Total Variance
Before
19922001 6/1610/16 1530N 123138E
After
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Before
9201
After
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before
after
15
1993
original
TC activity contributes half of intraseasonal
variance due to the clustering effect of ISO on
TC.
TC removed
from An-Kai Lo
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Interaction between ISO and TC
clustering effect
TC
ISO
TC
enhance ISO variability
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• Possible implication for climate simulation and
  prediction in the western North Pacific
• Fact
• Poor GCM simulation and low predictability in
  East Asia summer rainfall
• Better simulation
• Need reasonable simulation of ISO and TC ?