EL NIO-SOUTHERN OSCILLATIONS EFFECT ON AMERICAN TORNADOS Jake
Mittelman April 24 2012
Slide 2
Overview ENSO Tornados Data Hypothesis Periodogram Correlations
Bootstrap Jacknife Title Source:
http://en.wikipedia.org/wiki/Tornado Image Source:
http://dailypicksandflicks.com/wp-content/uploads/2012/04/Dallas-Tornado-Throwing-Semi-Trucks-and-Trailers.jpg
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El Nio-Southern Oscillation Quasiperiodic Tropical Pacific
Ocean Variations in SST El Nino Warm Phase La Nina Cool Phase Image
Source:
http://en.wikipedia.org/wiki/El_Ni%C3%B1o-Southern_Oscillation
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ENSO
Slide 5
Image Source:
http://en.wikipedia.org/wiki/El_Ni%C3%B1o-Southern_Oscillation El
Nino La Nina
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Tornados Severe Weather Instability Wind Shear Lifting Moisture
Moisture Tornados more likely with low LCL Can increase instability
Image Source:
http://en.wikipedia.org/wiki/File:Binger_Oklahoma_Tornado.jpg
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Hypothesis Whole U.S. Little to no correlation Southeast
Positive Correlation with El Nino Negative Correlation with La Nina
(Winter) Midwest Positive Correlation with La Nina Image Source:
http://en.wikipedia.org/wiki/File:Dimmit_Sequence.jpg
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Nino 3.4 Index 1950-2007 Middle Ocean NCAR CGDs Climate
Analysis Section Compute area averaged total SST from Nio 3.4
region. Compute monthly climatology (1950-1979) for area averaged
total SST from Nio 3.4 region, and subtract climatology from area
averaged total SST time series to obtain anomalies. Smooth the
anomalies with a 5-month running mean. Normalize the smoothed N3.4
by its standard deviation over the climatological period 1950-
1979. Image Source:
http://en.wikipedia.org/wiki/File:Enso-index-map.png
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Nino 3.4 Index
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Tornado Data Initial Problem Severe Weather Database from SPC
1950-2007 EF0-EF5
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LSQR On Tornado
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Pearson Correlation Coefficients Strength of Linear Dependence
Nino 3.4 & Tornado (all) r =.0411
El Nino and La Nina Correlations Southeast La Nina r = 0 El
Nino r = 0 Midwest (IL, IN, IA, KS, MI, MO, NE, ND, OH, SD, WI) La
Nina r =.11 El Nino r = -.06 Total r =.02 Total La Nina r =.13 El
Nino r = 0
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Periodograms
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CPSD
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Coherence
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Bootstrap Tends to be overly optimistic Seasons Still Working
On Summer r =.15
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Bootstrap
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Jackknife
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Other Research Cook, A. R., Schaefer, J.T. 2007 Used Tornado
Days Problem: Not a lot of Data Total ~220 Days Found Jet Stream
Movement Had Effect Used Trends Bove, Mark 1999 Boostrap Method to
Increase Data Most Places Show No Change Knowles, J., Pielke, R.
1993 Used 7 El Nino and 5 La Nina Events Found Little Difference in
Number But Found El Nino to have Weaker Tornado Outbreaks
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More I can Do Take out More Neutral ENSO Months Create Smaller
Areas Look at Numbers not Linear Correlations Image Source:
http://en.wikipedia.org/wiki/Tornado
Slide 25
Conclusion No Correlation Overall Number of Tornados and ENSO
Phase Go More Into Year ENSO still can have an effect Tornado
Strength Number per Outbreak Location Image Source:
http://uncyclopedia.wikia.com/wiki/File:Animated_tornado.gif
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Any Questions? Image Source:
http://www.google.com/imgres?imgurl=http://a.abcnews.com/images/US/Severe_Weather_110427_wg.jpg