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Geophysical Fluid Dynamics Laboratory Presented by Andrew

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									Tropical Climate Change and ENSO




            Presented by
          Andrew Wittenberg
     Geophysical Fluid Dynamics Laboratory
    Geophysical Fluid Dynamics Laboratory      NOAA
                                             GOES-11
                 17 October 2012             5 Oct 2011
                                             1800 UTC
                     The Tropics: Firebox of the global circulation




                                                                     Thompson
                                                                  Higher Education

Geophysical Fluid Dynamics Laboratory
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                           Projected surface temperature changes

      Vecchi et al. (2008)
   Vecchi & Wittenberg (2010)
      Collins et al. (2010)
        Xie et al. (2010)


     Strongest warming
         over land &
      equatorial Pacific

         More warming
         in calm areas,
           and where
         winds weaken

       Feedbacks from
         low clouds &
       ocean advection

Geophysical Fluid Dynamics Laboratory
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                                        Projected water vapor changes

   Vecchi & Wittenberg (2010)
      Collins et al. (2010)
        Xie et al. (2010)




            Tropics today:
         ~40 kg of water vapor




               2050: +4 kg


      Warming pumps
      water vapor into
      the atmosphere

Geophysical Fluid Dynamics Laboratory
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                                        Projected rainfall changes

     Held & Soden (2006)
   Vecchi & Wittenberg (2010)
      DiNezio et al. (2010)
        Xie et al. (2010)




           Broadly:
     “the wet get wetter,
      the dry get drier”.

          Over tropical
             oceans:
          “the warmer
           get wetter”.

Geophysical Fluid Dynamics Laboratory
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                    Projected tropospheric temperature changes

      Held & Soden (2006)
       Vecchi et al. (2006)
      Frierson et al. (2007)
       Collins et al. (2010)




          Increased
       static stability
       of atmosphere

        Helps expand
         Hadley Cell

          Weakens
         convective
       mass fluxes &
        trade winds

Geophysical Fluid Dynamics Laboratory
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                    Projected upper-ocean temperature changes

          DiNezio et al.
      (JC 2009, EOS 2010)
       Collins et al. (2010)




       Tropical ocean
       more stratified

           Stronger,
       shallower, and
      flatter equatorial
         thermocline

Geophysical Fluid Dynamics Laboratory
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                Earth's dominant interannual climate fluctuation




           Normal




           El Niño


                                                         NOAA/CPC

Geophysical Fluid Dynamics Laboratory
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                                      Projected ENSO changes (CMIP3/AR4)

                                                                                       Weak/ambiguous
                                                                                           near-term
                                                                                         anthropogenic
std(SLP.PC1 of SRES.A2 (2051-2100))


   van Oldenborgh et al. (OS 2005)




                                                                                       impacts on ENSO
      / std(SLP.PC1 of 20C3M)
          30S-30N, 30E-60W




                                                                             CM2.1         Intrinsic
                                                                                          modulation

                                                                                            Reviews:
                                                                                            Meehl et al.
                                                                                         (IPCC-AR4 2007)
                                                                                          Guilyardi et al.
                                                                                          (BAMS 2009)
                                                                                       Vecchi & Wittenberg
                                                                                        (WIREs CC 2010)
                                                                                            Collins et al.
                                       correl(SST trend of 1%/yr, SST.PC1 of PICTRL)   (Nature Geosci. 2010)
                                                     10S-10N, 120E-80W
                                               Yamaguchi & Noda (JMSJ 2006)

Geophysical Fluid Dynamics Laboratory
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                           Intrinsic modulation of ENSO: Observed

                                                                     Vecchi & Wittenberg
                                                                      (WIREs CC 2010)
                                        Historical SSTA (ERSST.v3)




      Palmyra corals
         (Cobb et al.,
        Nature 2003)


    Multiproxy reconstructions:
         Emile-Geay et al.
         (2011abc, subm.)

Geophysical Fluid Dynamics Laboratory
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                          Intrinsic modulation of ENSO: Simulated
                                                            Wittenberg (GRL 2009)




Geophysical Fluid Dynamics Laboratory
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                                    The most extreme ENSO epochs




                                                                   Wittenberg et al.
                                                                       (in prep.)

Geophysical Fluid Dynamics Laboratory
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                        Initial conditions for “perfect” reforecasts




                                                                       Wittenberg et al.
                                                                           (in prep.)

Geophysical Fluid Dynamics Laboratory
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                      40 “perfect” reforecasts – best possible skill




                                                                       Wittenberg et al.
                                                                           (in prep.)

Geophysical Fluid Dynamics Laboratory
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                         1860: Spread of 100yr NINO3 SST spectra

                                                          286 ppmv




                                                                   Wittenberg (2009)

Geophysical Fluid Dynamics Laboratory
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                               1990: Stronger annual cycle & ENSO

                                                              353 ppmv




                                                                     Wittenberg (2009)

Geophysical Fluid Dynamics Laboratory
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                                2xCO2: A perfect climate for ENSO?

                                                               572 ppmv




                                                                      Wittenberg (2009)

Geophysical Fluid Dynamics Laboratory
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                     4xCO2: Stronger annual cycle, weaker ENSO

                                                       1144 ppmv




                                                               Wittenberg (2009)

Geophysical Fluid Dynamics Laboratory
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                            Competing changes in ENSO feedbacks

           1. Amplifiers
                 - stronger rainfall & wind stress responses to SSTAs
                 - stronger thermocline, shallower mixed layer
                 - weaker replenishment of surface waters from below

           2. Dampers
                 - stronger evaporative & cloud-shading responses
                 - weaker upwelling -> surface less connected to thermocline
                 - smaller dynamic warm pool -> less room for warming

           3. Ambiguous effects
                 - stronger intraseasonal wind variability

                           Guilyardi et al. (BAMS 2009); Vecchi & Wittenberg (WIREs CC 2010)
                Collins et al. (Nature Geosci. 2010); DiNezio et al. (JC 2009; EOS 2010; JC 2011 subm.)
                                        Ongoing activities with CLIVAR Working Groups,
                      D. Battisti, A. Atwood, M. Cane, C. Karamperidou, F.-F. Jin, J. Brown, F. Graham

Geophysical Fluid Dynamics Laboratory
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                                           Summary

           1. Projections of tropical climate change
                 - tropics moisten, stratify, expand
                 - circulation weakens; ocean thermocline shoals & flattens
                 - SST: calm(er) get warmer; ocean advection changes
                 - rainfall: wet get wetter; warmer get wetter
                 - distinct from El Niño

           2. Is ENSO changing?
                 - diverse projections
                 - competing feedbacks + optima + model biases -> uncertainty

           3. Risk of intrinsic ENSO modulation
                 - ENSO capable of wide swings in behavior on its own
                 - interannual predictability only, except after a big event


Geophysical Fluid Dynamics Laboratory
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