Daehyun Kim, Yoogeun Ham

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Daehyun Kim, Yoo-geun Ham Climate Dynamics
Laboratory
2005. 3. 30
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Method in these papers - Composite

• Wu and Kirtman 2003
• In reality, ENSO and the monsoon are integral
  parts of the coupled system and interact with
  each other
• The monsoon anomalies include both ENSO-related
  and unrelated variations. Similarly, the Pacific
  SST anomalies likely have monsoon signals.
• This leads to difficulty in separating the wind
  anomalies induced by either ENSO or monsoon
  alone.
• Because of the tendency for a warm(cold) event
  to concur with a dry(wet) monsoon (Meehl 1987
  Webster and Yang 1992), the obtained anomalous
  circulation features display a high degree of
  similarity for these two types of composite.
• Thus the composites cannot separate the
  anomalies induced by the monsoon from those
  induced by ENSO.

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Monsoon and ENSO Signal or Noise?
CGCM (Interactive ensemble)
Real world
CGCM
AGCM
OGCM
Continuous, totally coupled
Discontinuous, coupled with few variables

• What we want to see?
• How can we interpret the result of model?

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Statistical appearance of monsoon-ENSO
relationship
Observation

• It is hard to analyze with OBS data because the
  period is short
• (for the many essential variables)
• In the model result, we can see that there is
  similar appearance of monsoon ENSO relationship

CGCM
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How the monsoon affect to ENSO?
In the weak monsoon period
anomalous depression
low level divergence
wind forcing to Ocean
Sea surface
Oceanic Kelvin wave propagation
ThermoclineDepth
Indian Ocean
Maritime continent
Pacific Ocean
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The effect of monsoon on ENSO 1. to warm phase
(model)
SSTA
Warm-normal(SSTA)
Heat contents
Wind
Warm-dry minus Warm-normal
Warm-wet minus Warm-normal
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The effect of monsoon on ENSO 2. to cold phase
(model)
SSTA
Cold-normal(SSTA)
Heat contents
Wind
Cold-dry minus Cold-normal
Cold-wet minus Cold-normal
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The effect of monsoon on ENSO 3. to normal phase
SSTA
Heat contents
Wind
Normal -Dry

• Even in the normal years, the monsoon effect is
  similar with in the warm and cold years

Normal -Wet
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The effect of monsoon on ENSO 4. observation
normal
dry-normal
wet-normal
Warm

• the amplitude is small
• but same sign with model

Cold
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The effect of monsoon on ENSO 4. observation
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Statistical appearance of monsoon-ENSO
relationship 2
Monsoon transition
ENSO transition
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Composite anomalies
Warm
Dry
Cold
Wet
Warm
Dry
Cold
Wet
Wet
Cold
Warm
Dry
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Moisture divergence caused by anomalous Walker
circulation
Wet
Cold
Dry
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Conclusion

• Indian monsoon can affect to the ENSO evolution
• a strong or weak monsoon has significant effects
  on an ongoing warm event through surface zonal
  wind-stress anomalies in the equatorial western
  central Pacific
• ENSO can affect to the Indian monsoon transition
• through modulating tropical east-west
  circulation over the tropical Indian and Pacific
  Oceans
• -gt low-level anomalous moisture convergence
  precondition of following monsoon

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Indian monsoon and ENSO relationship

• AnomalousSurface
• Easterly

• Air-seaInteraction

Cold Central Pacific
Strong monsoon

• Modulation
• of Walker
• Circulation

• Enhanced
• Moisture
• Convergence

• Reduced
• Moisture
• Convergence

• Modulation
• of Walker
• Circulation

Weak monsoon
Warm Central Pacific

• Anomalous
• Surface
• Westerly

• Air-seaInteraction

Thank you!
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TBO Tropical Biannual Oscillation
Meehl