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

Future Plans

Rolando Garcia

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Outline

1. WACCM overview

2. 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…

• Doug Kinnison (ACD)

• Dan Marsh (ACD)

• Katja Matthes (Free University Berlin)

• Astrid Maute (HAO)

• Jadwiga Richter (CGD)

• Fabrizio Sassi (CGD)

• Stan Solomon (HAO)

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

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and, of course, Byron Boville …

… to whose memory this talk is dedicated

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1. Overview of WACCM

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NCAR Whole Atmosphere Community Climate Model

MOZART-3

CAM3

WACCM-3

TIME-GCM

Chemistry

Dynamics +

Physical processes

MLT Processes

+ extensions

• Based on The Community Atmosphere Model (CAM3)

• 0-140 km (66 levels; z =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

WACCM

140 K

270 K

200 K

• SABER: broadband IR radiometer onboard TIMED satellite; measures T, O3, H2O, CO2

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Zonal-Mean U: JULY

WACCM

• URAP/UKMO: UARS/UK Met Office reference atmosphere, based upon UARS satellite observations

assimilated with the UK Met Office GCM

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Zonal-Mean O3 : JULY

11 ppm

WACCMSABER

• SABER: broadband IR radiometer onboard TIMED satellite; measures T, O3, H2O, CO2

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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

• 15 years ea. solar maximum and minimum conditions

• Smax: F10.7 = 210, Kp = 4• Smin: F10.7 = 77, Kp = 2.7

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

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SSU/MSU4 (1979-2003)

Courtesy of Bill Randel (2005)

WACCM (annual mean)Stratospheric temperature response

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SAGE I/II ozone change

2.4% 3.6%

% ozone change for 1% change in Mg II(~6% Mg II change over solar cycle)

WACCM (annual mean)

% ozone change over solar cycle

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Ozone column vs. f10.7 regressions: WACCM and observations

WACCM 1950-2003 WACCM 1979-2003

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• 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)

1950-2003 trends simulation

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Calculated and Observed Ozone Trends

SAGE-I 1979-1981 and SAGE-II 1984-2000

• Red inset on left covers approximately same region as observations on right• Agreement is quite good, including region of apparent “self-healing” in lower tropical stratosphere

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Total Column Ozone Trends (Global)

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Calculated and Observed Temperature Trends

SSU + MSU 1979-1998

• Red inset on left covers approximately same region as observations on right• Note comparable modeled vs. observed trend in upper stratosphere, although model trend is somewhat smaller

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Temperature Trends (Global), K / Decade

Courtesy of Bill Randel (NCAR)

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Whole-atmosphere zonal-mean T trend 1950-2003

Note lack of trend at 80-90 km

Ozone decrease and CO2 increase

CO2 increase(greenhouse effect)

Antarctic O3 hole

CO2 decrease

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• 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.

21st century prognostic simulations

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Global-mean ozone column

1950-2003 sim

1980-2050 sim(A1B scenario)

column minimum ~2000-2010

recovery to 1980 values ~2040

smoothed with 12-month running mean

• 21st century prognostic simulation (red) shown together with the results of the 1950–2003 simulation (black) discussed earlier

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Global-mean ozone column

all smoothed with 12-month running mean

A1B scenario

“no-climate change” scenario

• 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

1950-2003

1980-2050 A1B

1980-2050 fix

GHG

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• 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

Upper atmosphere dynamics: The 2-day wave

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SABER T Spectrum

Similar spectral behavior in WACCM calculations as in SABER data

Wavenumber/frequency T spectra at 36°N and 80 km (July)

Note concentration of variance along line of constant c in both

data and model

WACCM T Spectrum

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Components of 2-day wave in SABER data and WACCM simulation

k=3, ~2-day

SABER

k=4, ~1.8 day

SABER

SABER observations and WACCM results for July

WACMM WACMM

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… more components of 2-day wave in SABER data and WACCM

k=2, ~3 day

SABER

k=2, ~ 2 day

SABERWACCM 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