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Implication of Stratospheric Vortex Intensification on Climate Variability

Implication of Stratospheric Vortex Intensification on Climate Variability. Kumar Jeev (kjeev@coastal.edu) Coastal Carolina University Conway, South Carolina Faculty Mentor: Dr. Var Limpasuvan. Aim : Does the stratosphere affect the troposphere ? NAO and the Stratosphere Vortex

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Implication of Stratospheric Vortex Intensification on Climate Variability

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  1. Implication of Stratospheric Vortex Intensification on Climate Variability Kumar Jeev (kjeev@coastal.edu) Coastal Carolina University Conway, South Carolina Faculty Mentor: Dr. Var Limpasuvan • Aim : Does the stratosphere affect the troposphere ? • NAO and the Stratosphere Vortex • Tools & Methods • Stratosphere & NAO Index Composites • Wind and Temperature Anomalies • Conclusions

  2. The NAO High Phase • Stronger subtropical high • Deeper Icelandic Low • Increased pressure difference • Stronger storms move north • Warm & wet winters in Europe • Cold & dry winters in Canada • Mild & wet winters in East US • Intense “vortex” (circumpolar winds in stratosphere)

  3. The NAO Low Phase • Weak subtropical high • Weak Icelandic low • Less Pressure difference • Fewer storms move west • Mediterranean is moist • Northern Europe is cold • US east cost is cold & snowy • Weak stratospheric polar vortex

  4. Previous Study: Stratosphere-Troposphere Connection • Limpasuvan & Thompson [in prep]

  5. Tools – Indices Numerical description of phase/vortex strengths The NAM Index High Phase => greater than 0 Low Phase => less than 0 The Stratosphere Vortex Index Strong Vortex => greater than 0 Weak Vortex => less than 0

  6. Tools – NCEP Reanalysis Data (daily: 1958-2002) Variables air = temperature vwnd = meridian wind uwnd = latitudinal wind NP air vwnd lev uwnd Parameters Latitude Longitude Height (Lev) Time (Date) SP

  7. Methods: Lead-Lag Composite • Event Selection (25 events) Selecting time intervals • greater than 10 days • with stratospheric index > 1 • ending within that winter (not ending in late spring) The midday and 30 days before and after it form your event • Zonal Averaging • Sweeping the globe (average around latitude circle) • Compositing • Averaging over the 25 events • Finding Anomaly Anomaly = (Variable value) – (Climatological variable value)

  8. Index Average Comparison over an event -30 -15 0 +15 +30 -30 -15 0 +15 +30  60 days   60 days  The Stratosphere Index The NAO Index

  9. Temperature Anomalies Onset Mature Decay

  10. Wind Anomalies

  11. Conclusions and Future Work uwnd latitude time • Stratospheric vortex intensification leads to the NAO High • Wind and Temperature anomalies descend from upper stratosphere to middle troposphere during intensification • We are still looking into wave structure related to intense vortex • Momentum and Heat Fluxes • Wave forcing • We intend to use Global Climate Model to study the NAO and its relationship with the Stratosphere vortex

  12. Comments ! or Questions ?

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