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SLP Cyclone anti-cyclone asymmetry and time mean field

SLP Cyclone anti-cyclone asymmetry and time mean field. July 8, 2008. NCEP reanalysis 1948-2008, DJF No filtering. NH Time mean (raw) reflected about equator. Total wavenumber >=6. Normalized by STD^3. Skewness (contours) Time mean (colors. Example Fit. Histograms of extrema.

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SLP Cyclone anti-cyclone asymmetry and time mean field

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  1. SLPCyclone anti-cyclone asymmetryand time mean field July 8, 2008

  2. NCEP reanalysis 1948-2008, DJF No filtering

  3. NH Time mean (raw) reflected about equator Total wavenumber >=6

  4. Normalized by STD^3

  5. Skewness (contours) Time mean (colors

  6. Example Fit

  7. Histograms of extrema • Locate local (time) extrema in daily time series at each gridpoint • Can use a threshold to define unique extrema (doesn’t change much of the results) • Compile the histograms of positive and negative extrema • Do these look the same as raw data histogram?

  8. Mid-Atlantic

  9. North Pacific

  10. Mid_pacific

  11. South Pacific

  12. Tracking of SLP • All data is NCEP mean SLP from 1978-2008 DJFM, daily • Two pre-filtering routines are comparesd • Spatial filter that keeps total planetary wavenumber >= 6 (Hoskins); • A temporal, high pass filter (double pass, sixth order butterworth) with cutoff period of 20 days.

  13. hPa

  14. Define Regions over which the time mean, spatially filtered field is large

  15. North Pacific Histogram

  16. North Atlantic

  17. South (low lat) Pacific

  18. Can we explain the histogram differences by simple adding a time mean to the temporal data • Find the spatial average of the spatially filtered time mean SLP in each boxed domain • Add this constant to all the tracked data magnitudes • Compute the histograms alongside the spatially filtered tracked data

  19. TRACKS AND COMPOSITES BY REGION • Take the 100 largest storms in each region (that way number of tracked features doesn’t get in the way) • Plot tracks, all is lagrangrian data defined by the filter used • Composite around the 100 features onto the RAW SLP Eulerian fields relative to storm center • In plots, the spatial mean of the composite field is subtracted for visual purposes.

  20. Look in the middle of the Atlantic, where there is a node in the mean

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