Climatic variability of dynamics in the winter stratosphere Kanukhina A.Y. Suvorova E.V.

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Climatic variability of dynamics in the winter
stratosphere

Kanukhina A.Y.

Suvorova E.V.
Ulyanets E.K.

Pogoreltsev A.I. 9-13,September,2007

• The Russian State Hydrometeorological
  UniversitySt.Petersburg

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Why it is important?

• A strong longitudinal inhomogeneity of
  meteorological fields is one of the main
  properties of stratospheric dynamics during
  winter. The fundamental problem of atmospheric
  dynamics including seasonal, interannual, and
  decadal variability of temperature and planetary
  wave activity within the troposphere and
  stratosphere, as well as possible effects within
  middle atmosphere caused by these changes becomes
  increasingly relevant for climate research.
• The reason
• the need to study dynamical and photochemical
  processes impacts on observed climatic changes of
  atmospheric temperature
• there is a growing evidence that additional
  extended-range tropospheric forecast skill may
  also come from slow variations of the circulation
  and planetary waves in the stratosphere

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Planetary waves

• oscillations with typical periods of about 230
  days
• large-scale (global) character
• predominantly of tropospheric origin
• 2 types
• 1 - the stationary planetary waves (SPW),
  associated with the quasi-steady meteorological
  structures
• 2 - the travelling planetary waves, which
  propagate predominantly westward, even though
  sometimes (rarely) the eastward propagation
  dominates

• Example of Saturns waves of ionized particles
  http//photojournal.jpl.nasa.gov/catalog/PIA09186

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The main objectives

• analysis of SPW of zonal wavenumber 1 and 2 (not
  shown here) from NCEP/NCAR data since 1959
• interannual, interdecadal and long-term SPW
  variability analysis
• numerical simulation of SPW propagation with
  linearized model and stratospheric background
  conditions that are characteristic for different
  decades, comparison of stratospheric reanalyses
  with numerical model results
• analysis of middle and upper atmosphere
  variability due to SPW based on numerical
  results, and comparison with experimental results
  from literature.

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Previous results

• noticeable climatic changes of the temperature in
  the lower atmosphere which have different signs
  at low and high latitudes
• changes of the positions and intensity of
  tropospheric jets are in a good agreement with an
  increase of temperature latitudinal gradient
• the results of simulation with the background
  zonal wind typical for 1960 and 2000 show an
  increase in amplitude of the SPW1 in the
  stratosphere and mesosphere of the winter
  hemisphere during the last decades

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Modeled amplitudes of geopotential height
disturbances for SPW1 1960
2000

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NCEP/NCAR (National Center for Environmental
Prediction - National Center for Atmospheric
Research) data

• Temperature, geopotential height and zonal wind
  distribution in the tropo- and stratosphere
• in December, January and February during 1948
  and 2007 period of NCEP re-analysis
• 2,50 2,50 grid, 6 hours interval
• Global Grids with 144x73 points
• 1000, 500, 400, 300, 200, 100, 30, 10 hPa levels
• Scientific Reference
• Kistler, R., E. Kalnay, W. Collins, S. Saha,
  G. White, J. Woollen, M. Chelliah, W. Ebisuzaki,
  M. Kanamitsu, V. Kousky, H. van den Dool, R.
  Jenne, M. Fiorino, 2001Bulletin of the American
  Meteorological Society, Feb2001, Vol. 82 Issue 2,
  p247

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• SPW1 amplitude variations (geopotential height)
• 30 hPa level, 62.5 north

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Interpretation of wavelet spectra for travelling
waves

• If AwAe --gt
• ÃwAw-Ae, Ãspw2Ae, Ãe0
• If AwltAe,
• ÃeAe-Aw, Ãspw2Aw, Ãw0
• Ãe, Ãw recalculated eastward and westward PW
  amplitudes
• Ãspw recalculated periodical change of SPW
  amplitudes

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Amplitude wavelet spectra for SPW
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Amplitude wavelet spectra for travelling PW
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Averaged over 1959-2007 spectra for SPW and
westward propagating waves m1, 30 hPa level,
62 N
See next slide (enlaged image)
SPW
Westward wave
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Averaged over 1959-2007 Spectra for SPW and
westward propagating wavesm1, 30 hPa level, 62
N
SPW
Westward wave
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Variability of SPW and 5 day wave amplitudes,
m1, 30 hPa level, 62 N




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Variability of the 10 and 16 - day wave
amplitudes, m1, 30 hPa level, 62 N




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Summary and results

• during the last decades the winter-time averaged
  amplitude of SPW1 increases at the higher-middle
  latitudes of the Northern Hemisphere
• the growth in the amplitude of the stratospheric
  vacillations
• the amplitudes of longer-period normal
  atmospheric modes or the so-called 10- and 16-day
  waves diminish
• stratospheric dynamics becomes more stochastic
• Growth of vacillations amplitude leads to
  increasing travelling PW amplitudes but it isnt
  so. Possible reason is CO2 concentration rising
  (intensifying of radiative dumping and resonance
  quality fall escpessially for normal modes of low
  frequency).

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Future work

• perform similar analysis for July to estimate
  interhemispheric differences
• Estimate the tropospheric manifestations of the
  changes in stratospheric dynamics, and effects in
  the upper atmosphere caused by these changes

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Thank you for attention !