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Simulating the extratropical response to the Madden-Julian Oscillation

Simulating the extratropical response to the Madden-Julian Oscillation. Hai Lin RPN-A, Environment Canada International S2S Conference, College Park February 10-13, 2014. Introduction. MJO Global impact (boreal winter): NAO (Lin et al 2009); PNA (Mori and Watanabe 2008)

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Simulating the extratropical response to the Madden-Julian Oscillation

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  1. Simulating the extratropical response to the Madden-Julian Oscillation Hai Lin RPN-A, Environment Canada International S2S Conference, College Park February 10-13, 2014

  2. Introduction • MJO • Global impact (boreal winter): NAO (Lin et al 2009); PNA (Mori and Watanabe 2008) AO (L’Heureux and Higgins 2008) Canadian temperature (Lin and Brunet 2010) Canadian precipitation (Lin et al 2010) • Atmospheric response to MJO forcing: Matthews et al. (2004) Lin et al. (2010) Seo and Son (2012)

  3. Outlines • Introduction • Numerical experiments: Dependence on heating location Nonlinearity Dependence on initial condition • Summary

  4. Correlation when PC2 leads PC1 by 2 pentads: 0.66 Lin et al. (2010)

  5. Normalized Z500 regression to PC2 Lin et al. (2010)

  6. Model and experiment • Primitive equation AGCM (Hall 2000) – similar configuration of model forcing as the Marshall-Molteni model, but not Q-G. • T31, 10 levels • Time-independent forcing to maintain the winter climate • Linear integration, winter basic state

  7. Thermal forcing Exp1 forcing Exp2 forcing Lin et al. (2010)

  8. Z500 response Exp1 Exp2 Lin et al. (2010)

  9. Why the response to a dipole heating is the strongest ? • Linear integration, winter basic state • with a single center heating source • Heating at different longitudes along the equator from 60E to 150W at a 10 degree interval, 16 experiments • Z500 response at day 10

  10. 80E Day 10 Z500 linear response Similar pattern for heating 60-100E 110E 150E Similar pattern for heating 120-150W

  11. Questions: • Are the responses to opposite signs of MJO forcing mirror images? (nonlinearity) • Which response is less sensitive to initial condition and background flow? with less spread? • How does the response depend on extratropical jet initial condition?

  12. Nonlinearity • 3 sets of experiments: 1) Control 2) +MJO forcing 3) –MJO forcing • From 360 different initial conditions • 30-day nonlinear integrations

  13. Thermal forcing +MJO thermal forcing Exp1 forcing Exp2 forcing Lin et al. (2010)

  14. Nonlinearity Z500 response

  15. spread +MJO response has less spread, less sensitive to initial condition

  16. EOF of 360 Z500 day 6-10responses to the same +MJO Downstream shift Intensify

  17. Dependence on initial condition U200 Jet intensifies Jet moves southward

  18. Summary • There is significant nonlinearity in response in mean response and spread • Response to –MJO is more sensitive to initial condition (when the heating is over central Pacific) • Response sensitive to the strength and position of East Asian jet • Implication to subseasonal forecasting: MJO phase and jet initial condition

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