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Indian summer monsoon and ENSO (Wu and Kirtman 2003, 2004) PowerPoint PPT Presentation

Indian summer monsoon and ENSO (Wu and Kirtman 2003, 2004) Daehyun Kim, Yoo-geun Ham Climate Dynamics Laboratory 2005. 3. 30 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

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Indian summer monsoon and ENSO (Wu and Kirtman 2003, 2004)

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Indian summer monsoon and ENSO

(Wu and Kirtman 2003, 2004)

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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AGCM

AGCM

Atmosphere

Ocean

OGCM

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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zonal advection

mean upwelling

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

Heat contents

Wind

Warm-normal(SSTA)

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

Heat contents

Wind

Cold-normal(SSTA)

Cold-dry minus

Cold-normal

Cold-wet minus

Cold-normal


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The effect of monsoon on ENSO – 3. to normal phase

Heat contents

Wind

SSTA

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

ENSO transition

Monsoon transition


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Composite anomalies

Warm

Dry

Cold

Wet

Warm

Dry

Cold

Wet

Wet

Cold

Warm

Dry


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Divergence

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

  • -> 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

Warm Central Pacific

Weak monsoon

  • Anomalous

  • Surface

  • Westerly

  • Air-seaInteraction

Thank you!


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TBO – Tropical Biannual Oscillation

Meehl


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