Stratosphere � Troposphere Coupling Mechanism

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Stratosphere � Troposphere Coupling Mechanism Powered By Docstoc
					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
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)
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
Previous Study: Stratosphere-Troposphere
Connection




                           Limpasuvan & Thompson [in prep]
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
   Tools – NCEP Reanalysis Data (daily: 1958-2002)

Variables                      NP          air
air = temperature
vwnd = meridian wind
                           vwnd
uwnd = latitudinal wind
                                                 lev
                                    uwnd
Parameters
Latitude
Longitude
Height (Lev)
                               SP
Time (Date)
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)
 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
Temperature Anomalies




 Onset           Mature   Decay
Wind Anomalies
                                            uwnd


    Conclusions and Future Work


                                                   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
Comments !
    or
Questions ?

				
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posted:9/1/2012
language:English
pages:12