MJOENSO interactions

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MJO-ENSO interactions

• Discussion items
• Axel Timmermann, Chidong Zhang

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Slingos strawman, revisited
????
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State dependence of WWBs
From Eisenman
What physical mechanisms determine the
state-dependence of WWBs? What effect does the
state-dependence have on ENSO predictability? What
effect does the state-dependence have on the
seasonal evolution of ENSO?
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(Why) Did the MJO-ENSO interaction increase?
MJO-ENSO interaction increased during the last
50 years from Jin et al. 2007 Is there still a
data-issue?
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Why are CGCMs doing such a poor job in simulating
the MJO? What basic process is misrepresented? Wha
t effect does the state-dependence have on the
seasonal evolution of ENSO?
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Precipitation spectra in Demeter
Lin et al.
Space-time spectrum of 15N-15S symmetric
component of precipitation divided by the
background spectrum
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But progress is happening
3.5km resolution
From Satoh, NICAM model
From GFDL
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But progress is happening
Lag Correlation between Noise Variance and ENSO
indices
NCEP/NCAR Coupled control simulation
SNU Coupled control simulation SNU with
Cumulus momentum transfer (CMT) CMT mixes down
westerly momentum Intensifies noise variance
probably by Rossby wave instability
Courtesy of Kug, 2007
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Key Issues

• What are the relative roles of additive and
  multiplicative noise in different basic states or
  different ENSO regimes (unstable-chaos,
  unstable-limit cycle, neutral, stable)? What are
  the contributions to additive and multiplicative
  stochastic forcing of ENSO from the MJO and WWB?
• To what degree do misrepresentations of the
  MJO/WWB in coupled models affect their ENSO
  prediction? What are scientific and practical
  merits to empirically correct such
  misrepresentations for improving ENSO prediction?
  To what degree would better MJO/WWB
  representations in coupled models improve their
  ENSO prediction?
• Do ENSO - MJO/WWB relationships vary on decadal
  or longer timescales? If they do, to what extent
  does this suggest an effect of the changing basic
  state on the receptiveness of ENSO to stochastic
  forcing or on stochastic forcing itself? What are
  its implications to ENSO prediction and
  predictability?
• How should various CLIVAR and broader WCRP and
  regional activities be coordinated to expedite
  the progress of improving the representations of
  the MJO in CGCMs for the purpose of improving
  ENSO prediction?

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Coordinated experiments and diagnostics

• Develop standardized diagnostics for CGCMs and
  observations to quantify (a) ENSO - stochastic
  forcing (distinguishing the MJO and non-MJO WWB)
  connections, and (b) the additive and
  multiplicative nature of stochastic forcing
  (especially the MJO and WWB)
• Recommend CGCM centers/groups to use the
  standardized diagnostics to evaluate their models
• Suggest coordinated CGCM experiments (with
  improved parameterizations) to be compared and
  evaluated with the standardized diagnostics
  resolve diurnal cycle, cumulus momentum transfer

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Plan

• Write a review paper on Stochastic forcing of
  ENSO (authors needed, more discussion in Pacific
  panel meeting)