The Whole Atmosphere Community Climate Model: Overview, Current Research and Future Plans

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The Whole Atmosphere Community Climate Model
Overview, Current Research and Future Plans

• Rolando Garcia

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Outline

• WACCM overview
• Research with WACCM
• Solar cycle impacts
• 1950-2003 trend simulations
• 21st century prognostic simulations
• Upper atmosphere dynamics (2-day wave)
• 3. Future work

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Acknowledgments
the following colleagues contributed to the work
presented in this talk . . .

• Doug Kinnison (ACD)
• Dan Marsh (ACD)
• Katja Matthes (Free University Berlin)
• Astrid Maute (HAO)
• Jadwiga Richter (CGD)
• Fabrizio Sassi (CGD)
• Stan Solomon (HAO)

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1. Overview of WACCM
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NCAR Whole Atmosphere Community Climate Model

• Based on The Community Atmosphere Model (CAM3)
• 0-140 km (66 levels Dz 1.3 km in lower
  stratosphere to 3 km in thermosphere)
• Finite-volume dynamics
• 30 minute time step
• MOZART-3 chemistry package (55 species)
• Upper atmosphere extensions
• Lindzen GW parameterization
• Molecular diffusion
• NO cooling
• non-LTE long-wave heating in the 15 µm band of
  CO2 and the 9.6 µm band of O3

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WACCM3 additions

• The following processes are now dealt with in a
  self-consistent manner in WACCM
• Solar variability
• Chemical heating
• Airglow
• Ion chemistry (5 ion species electrons)
• EUV and X-ray ionization
• Auroral processes
• Particle precipitation
• Ion drag
• Joule heating
• Chemistry is completely interactive with dynamics

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Current interdivisional collaborators

• Current external collaborations
• Mark Baldwin (NWRA)
• annular modes
• Natalia Calvo (U. of Madrid) and Marco Giorgetta
  (MPI, Hamburg)
• effects of ENSO on the middle atmosphere
  comparison of models and reanalysis data
• Charlie Jackman (NASA/Goddard)
• impacts of solar proton events on ozone
• Judith Perlwitz and Martin Hoerling
  (NOAA/Boulder)
• climate impacts of changing chemistry and SST
• Cora Randall et al. (CU/LASP) plus John Gille
  (ACD/HIRDLS) and Laura Pan (ACD/UTLS initiative)
• process-oriented evaluation of
  chemistry-climate models vs. observations

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Zonal-Mean T JULY
140 K
270 K
200 K
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Zonal-Mean U JULY
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Zonal-Mean O3 JULY
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2. Research with WACCM
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Solar min/max simulations

• Fixed solar minimum and solar maximum conditions
  (constant F10.7 and Kp typical of minimum/maximum)

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definition of solar variability

• Photolysis and heating rates are parameterized
  in terms of f10.7 and Kp

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Stratospheric temperature response
SSU/MSU4 (1979-2003)
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Ozone column vs. f10.7 regressions WACCM and
observations
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1950-2003 trends simulation

• An ensemble of retrospective runs, 1950-2003,
  including solar variability, observed SST,
  observed trends in GHG and halogen species, and
  observed aerosol surface area densities (for
  heterogeneous chemistry)

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Calculated and Observed Ozone Trends
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Total Column Ozone Trends (Global)
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Calculated and Observed Temperature Trends
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Temperature Trends (Global), K / Decade
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Whole-atmosphere zonal-mean T trend 1950-2003
CO2 increase (greenhouse effect)
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21st century prognostic simulations

• An ensemble of prognostic runs, 1975-2050, to
  look at climate change and ozone recovery in the
  21st century. Follows WMO A1B scenario.
• An additional ensemble assumed constant CO2, CH4,
  N2O to assess the role of stratospheric cooling
  by these gases.

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Global-mean ozone column
recovery to 1980 values 2040
1950-2003 sim
1980-2050 sim (A1B scenario)
smoothed with 12-month running mean
column minimum 2000-2010

• 21st century prognostic simulation (red) shown
  together with the results of the 19502003
  simulation (black) discussed earlier

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Global-mean ozone column

• A1B scenario produces super-recovery compared
  to no climate change simulation wherein CO2,
  N2O, CH4 are held at 1995 values.
• This is due to colder stratospheric T in A1B
  scenario.

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Stratospheric age of air is also affected by
changing GHG
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Upper atmosphere dynamics The 2-day wave

• Apart from the tides, the 2-day wave dominates
  high-frequency variability in the MLT
• Has large amplitude at solstice, especially in
  the summer hemisphere
• Has been interpreted as a normal mode (e.g.,
  Salby, 1981), a result of baroclinic instability
  (e.g., Plumb, 1983), and a combination of both
  (e.g., Randel, 1994)
• Comparison of WACCM simulations and observations
  by the SABER instrument on the TIMED satellite

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Similar spectral behavior in WACCM calculations
as in SABER data
Wavenumber/frequency T spectra at 36N and 80 km
(July)
WACCM T Spectrum
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Components of 2-day wave in SABER data and WACCM
simulation
SABER observations and WACCM results for July
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more components of 2-day wave in SABER data
and WACCM
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3. Future Work

• Climate sensitivity to doubling CO2 CAM vs.
  WACCM
• Impact of ozone hole and changing tropical SST
  on Arctic/Antarctic surface climate
• Climatology of stratospheric sudden warmings
  impacts of resolution, gravity wave
  parameterization, SST variability relationship
  to annular modes
• Process-oriented evaluation of model chemistry
  (comparisons with EOS/Aura observations)
• Impact of solar proton events on mesospheric and
  stratospheric composition
• Energy budget and dynamics of the MLT
  comparison with SABER observations

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To keep in touch . WACCM website and new model
release

• WACCM website is being hosted under ACD
  (http//waccm.acd.ucar.edu/index.shtml)
• Website has been updated and reformatted
• 2006 CSL proposal posted on site
• WACCM3 description to be completed
• Release WACCM3 in summer 2006