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Seminar MJO Hamilton

Seminar MJO Hamilton

Extra-tropical impacts of the Madden-Julian-Oscillation over New Zealand from a weather regime perspective

Nicolas Fauchereau

February 15, 2016
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  1. Extra-tropical impacts of the
    Madden-Julian-Oscilla8on over
    New Zealand from a weather
    regime perspec8ve*
    Nicolas Fauchereau1
    Benjamin Pohl2
    Andrew Lorrey3
    * Journal of Climate, in press, DOI hEp://dx.doi.org/10.1175/JCLI-D-15-0152.1
    1: NIWA, Hamilton, New Zealand
    2: Centre de Recherches de Climatologie, Dijon, France
    3: NIWA, Auckland, New Zealand

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  2. Who is this guy ?
    •  Nicolas (Nico) Fauchereau
    •  Ph. D. in France in 2004
    •  One year post-doc in Paris: stats, EVT, Weather
    Regimes over NA / Europe
    •  Post-doctoral fellowship at the ocean. dept., University
    of Cape-Town: scale-interac8ons in the climate system
    •  Senior Researcher at the CSIR (Cape-Town): climate
    controls on primary produc]on in the Southern Ocean
    •  Joined NIWA in 2012 (in Auckland): from paleo-climate
    reconstruc]ons to seasonal forecas]ng

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  3. Interests
    •  Sta]s]cs
    •  Time-series analysis (EMD, wavelets, etc.)
    •  Machine Learning
    •  Scien]fic Compu]ng (Python !)
    •  Open source and open science (Soaware
    Carpentry instructor)
    •  Surf !

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  4. Back to science !

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  5. What is the Madden-Julian-Oscilla8on
    (MJO) ?

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  6. •  An oscilla8on in tropical climate discovered by Roland
    Madden and Paul Julian in 1971
    •  Largest mode of intra-seasonal variability in the
    tropics
    •  Involves coupling between deep convec]on,
    atmospheric circula]on, SSTs
    •  Propagates eastward at ~ 4 to 8 m/s: typically circles
    the globe in 30 to 60 days: intra-seasonal

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  7. From: hEps://www.climate.gov/news-features/blogs/enso/what-mjo-and-why-do-we-care
    “dipole” in convec8on, precipita8on, etc.

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  8. Measuring and monitoring the MJO
    Wheeler and Hendon (2004):
    EOF of combined OLR, zonal wind at 850 and 200 hPa
    in the tropics
    First 2 PCs (RMM1 & RMM2) are in quadrature
    Composite OLR anomalies
    (Nov. – Mar.)
    Phase space representa]on of the MJO propaga]on

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  9. The MJO significance in the tropics
    – Rainfall
    – SSTs
    – Subsurface ocean (> 1500m deep !)
    – Tropical Cyclones
    – …

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  10. The MJO outside the tropics: impacts,
    predictability
    Northern Hemisphere:
    –  European sector (Cassou 2008, Nature)
    –  American sector (Riddle et al 2012, J. Climate)
    Weather Regime (WR) view (WR~ aEractor basins in the phase
    space of the atmospheric circula]on / recurrent archetypes in
    circula]on anomalies)
    Interac]ons with the Arc]c Oscilla]on (AO) / North Atlan]c
    Oscilla]on (NAO) regimes
    Significant source of predictability (Cassou 2008) at ]me-scales >
    15 days

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  11. Southern Hemisphere:
    –  South Africa (Pohl, Fauchereau et al, 2010)
    –  South America (Carvalho, 2008)
    –  Southern high la]tudes (debatable)
    –  Interac]ons possible with the Southern Annular Mode
    (debatable)
    No Weather Regime view
    No discussion of poten8al for predictability
    The MJO outside the tropics: impacts,
    predictability

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  12. This study
    •  Is there a signal of the MJO over NZ ?
    •  Can we explain it adop]ng the paradigm of
    weather regimes ?
    •  Is there any poten]al for predictability for NZ
    climate arising from the MJO ?
    •  Is the Southern Annular Mode involved ?

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  13. The MJO over the NZ sector
    rainfall
    circula]on

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  14. The MJO over the NZ sector
    Interac]ons with
    topography

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  15. The MJO over the NZ sector
    ~ Opposite spa]al
    PaEerns between
    opposite phases of
    the MJO
    Interac]ons with
    topography

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  16. Weather regimes and the Kidson
    Types
    •  WRs: aYractors in the climate system
    •  Archetypes in atmospheric circula]on
    •  Usually extracted using clustering methods
    •  Provide the link between weather (day to day variability) and climate (e.g. large-scale
    modes of variability)
    North Atlan]c / European WRs

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  17. •  Kidson (2000): EOF then k-means clustering of 1000 hPa NCEP / NCAR field (1958-1997)
    •  Updated on an opera]onal basis (Renwick, 2011)
    •  12 “types” (WRs)
    •  3 “regimes” (groups)
    Circula]on (1000 hPa) and rainfall anomalies associated
    with each KT

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  18. A regime view of the MJO signal
    How is the probability of the Kidson Types modulated by the MJO ?
    Test is based on a Monte-Carlo approach using 10000 ar]ficial realiza]ons (discrete ]me Markov Chains)
    of the Kidson Types sequences
    MJO phase
    Kidson Types

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  19. A regime view of the MJO signal
    “Zonal” WRs occurences increased during the 1st half of the MJO cycle / reduced during the 2nd half

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  20. A regime view of the MJO signal
    NE type (WR) almost 2 8mes more likely than normal during phase 6 of the MJO

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  21. A regime view of the MJO signal

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  22. Predictability ?
    Lag (days)
    Kidson Type

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  23. Predictability ?
    •  Significant changes in the
    frequency of some WRs up to ~
    20 days aaer given MJO phase is
    observed

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  24. Predictability ?
    •  Significant changes in the
    frequency of some WRs up to ~
    20 days aaer given MJO phase is
    observed
    •  Difference (in days) between the
    ]ming of ~ maximum delayed
    response consistent with MJO
    phase speed.

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  25. Summary
    •  Significant impacts of the MJO on NZ
    •  Explained partly by changes in the probability
    or regional Weather Regimes (Kidson types)
    •  Lagged rela]onships
    •  Not primarily mediated by the Southern
    Annular Mode
    •  Poten]al for predictability beyond
    meteorological ]me-scales

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  26. Supplementary slides

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