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Lagged Influence of Autumn Eurasian Snow and Arctic Sea-Ice on Winter NAO

This study investigates the predictability of the winter North Atlantic Oscillation (NAO) by examining the lagged influence of autumn Eurasian snow and Arctic sea-ice. The Extended Maximum Covariance Analysis (EMCA) approach is used to capture the time-evolving predictors. The study explores upward-propagating wave activity and transient-eddy feedback mechanisms that impact the polar vortex in the stratosphere and troposphere.

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Lagged Influence of Autumn Eurasian Snow and Arctic Sea-Ice on Winter NAO

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  1. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013 On the predictability of the winter NAO: lagged influence of autumn Eurasian snow and Arctic sea-ice J. García-Serrano, C. Frankignoul, G. Gastineau LOCEAN-IPSL, UPMC, Paris, France

  2. SNOWweek 1 SNOWweek 2 SNOWweek 3 SNOWweek 4 SNOWweek 5 NACLIM CT1 annual meeting, Trieste, 1-2/10/2013 Extended Maximum Covariance Analysis (EMCA) our approach relies on capturing time-evolving predictor in covariance with the winter NAO, but holding its spatial pattern; by means of introducing different time-lags in the MCA analysis Polo et al. & García-Serrano et al. (2008, J.CLIM) ERA-Interim (SD): 1979-2012 NOAA/NSIDC (SCE): 1966-2012 NOAA-CIRES 20CR (SD): 1966-2010 common period 1979-2010 (October) SLP (DJF) Y = nsSLP x nyr X = ( NLAGw * nsSNOW ) x nyr COV = ( X * Yt ) / nyr-1

  3. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013 EMCA-SCE (oct) scf=51.2% ruv=0.77

  4. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013

  5. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013 upward-propagating wave activity (stratospheric mechanism) at 100hPa

  6. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013

  7. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013 transient-eddy feedback(tropospheric mechanism) at 200hPa

  8. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013

  9. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013 upward-propagating wave activity (stratospheric mechanism) at 100hPa

  10. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013

  11. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013

  12. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013 transient-eddy feedback (tropospheric mechanism)

  13. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013 transient-eddy feedback (tropospheric mechanism)

  14. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013 • Summary: • Both, October Eurasian SCE and autumn (Sep-Oct-Nov) Arctic SIE expansion coefficients have a correlation of ~0.7-0.8 with winter Euro-Atlantic SLP variability. • October Eurasian SCE leads to changes in the Siberian High, which further lead to enhanced/reduced vertical wave activity over eastern Eurasia, affecting the stratospheric polar vortex over the North Pacific sector. • Arctic SIC triggers a wavetrain crossing Eurasia in November that (i) impacts vertical wave activity over both the North Pacific and northern European sectors, hence affecting the polar vortex; and (ii) induces transient-eddy feedback over the eastern North Atlantic basin helping to maintain and amplify the tropospheric anomaly. • The winter NAO and EMCA-SCE (October Eurasian SCE) show significant negative correlations over the Kara-Barents Seas in autumn, i.e. SIC reduction over the eastern Arctic, in agreement with MCA-SIC patterns. • There is a negative feedback in SIC over the eastern Arctic between autumn (negative anomalies - reduction) and winter (positive anomalies - increase), which is mediated by the NAO.

  15. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013 SIC (oct) SIC (nov)

  16. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013 • Summary: • Both, October Eurasian SCE and autumn (Sep-Oct-Nov) Arctic SIE expansion coefficients have a correlation of ~0.7-0.8 with winter Euro-Atlantic SLP variability. • October Eurasian SCE leads to changes in the Siberian High, which further lead to enhanced/reduced vertical wave activity over eastern Eurasia, affecting the stratospheric polar vortex over the North Pacific sector. • Arctic SIC triggers a wavetrain crossing Eurasia in November that (i) impacts vertical wave activity over both the North Pacific and northern European sectors, hence affecting the polar vortex; and (ii) induces transient-eddy feedback over the eastern North Atlantic basin helping to maintain and amplify the tropospheric anomaly. • The winter NAO and EMCA-SCE (October Eurasian SCE) show significant negative correlations over the Kara-Barents Seas in autumn, i.e. SIC reduction over the eastern Arctic, in agreement with MCA-SIC patterns. • There is a negative feedback in SIC over the eastern Arctic between autumn (negative anomalies - reduction) and winter (positive anomalies - increase), which is mediated by the NAO.

  17. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013

  18. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013 • Summary: • Both, October Eurasian SCE and autumn (Sep-Oct-Nov) Arctic SIE expansion coefficients have a correlation of ~0.7-0.8 with winter Euro-Atlantic SLP variability. • October Eurasian SCE leads to changes in the Siberian High, which further lead to enhanced/reduced vertical wave activity over eastern Eurasia, affecting the stratospheric polar vortex over the North Pacific sector. • Arctic SIC triggers a wavetrain crossing Eurasia in November that (i) impacts vertical wave activity over both the North Pacific and northern European sectors, hence affecting the polar vortex; and (ii) induces transient-eddy feedback over the eastern North Atlantic basin helping to maintain and amplify the tropospheric anomaly. • The winter NAO and EMCA-SCE (October Eurasian SCE) show significant negative correlations over the Kara-Barents Seas in autumn, i.e. SIC reduction over the eastern Arctic, in agreement with MCA-SIC patterns. • There is a negative feedback in SIC over the eastern Arctic between autumn (negative anomalies - reduction) and winter (positive anomalies - increase), which is mediated by the NAO.

  19. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013 On the predictability of the winter NAO: lagged influence of autumn Eurasian snow and Arctic sea-ice EXTRA SLIDES

  20. Honda et al. (2009, GRL)

  21. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013

  22. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013

  23. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013

  24. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013

  25. NACLIM CT1 annual meeting, Trieste, 1-2/10/2013

  26. The research leading to these results has received funding from the European Union 7th Framework Programme (FP7 2007-2013), under grant agreement n.308299 NACLIM www.naclim.eu

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