Information of Potential use to the IPCC lead authors and the AR4

Model Information of Potential Use to the IPCC Lead Authors and the AR4.

GISS-AOM

16 February 2005

I. Model Identity:

A. Institution: NASA Goddard Institute for Space Studies (NASA/GISS),

USA

B. Model name: AOM 4x3

C. Vintage: AOM 5x4 was first published in 1995;

AOM 4x3 was completed in 2004

D. References: Web site for AOM 4x3: http:/aom.giss.nasa.gov

Refereed publication of AOM 5x4 formulation:

Russell GL, Miller JR, Rind D, 1995. A coupled

atmosphere-ocean model for transient climate change

studies. Atmosphere-Ocean 33 (4), 683-730.

E. Model performance: of AOM 5x4:

Lucarini L, Russell GL, 2002. Comparison of

mean climate trends in the northern hemisphere

between National Centers for Environmental

Prediction and two atmosphere-ocean model

forced runs. JGR, 107 (D15),

10.1029/2001JD001247

F. Climate sensitivity: Early version of AOM 5x4 was estimated to

have dTeq = 2.65 (C) for doubling CO2 by

diagnosing ocean heat intake;

AOM 4x3 has not been examined

G. Contacts: For all pieces: Gary L. Russell,

Gary.L.Russell@nasa.gov

II. What can be included (interactively) and was it active in the model

version that produced output stored in the PCMDI database?

A. Atmospheric chemistry: no

B. Interactive biogeochemistry: no

C. Aerosols: Boucher's monthly-decade sulfate burden (mg/m^2)

(downloaded from PCMDI web site) was converted to an

optical depth by global coefficient [.030 (m^2/mg)]

and treated as tropospheric sulfate aerosols with

particular vertical distribution;

indirect effects were not separately modeled

D. Dynamic vegetation: no

E. Ice sheets: nothing other than that covered under IV. D. 9.

III. Projects: AMIP: 5x4 atmospheric model between AOM 5x4 and AOM 4x3

CMIP: early version of AOM 5x4, should be discarded

IV. Component model characteristics (of current IPCC model version):

A. Atmosphere

1. Resolution: 4 degrees longitude, 3 degrees latitude, 12

vertical layers, heat and water vapor have mean

value and three prognostic directional gradients

inside each cell

2. Numerical scheme: grid point model;

forward step, linear upstream shceme used

for linear advection (heat and water vapor);

leap frog, second order center-difference

C-grid scheme for non-linear advection

(momentum);

combination of fixed mass and sigma

coordinate vertical layering;

4 layers above 204 hPa on average;

2 layers below 875 hPa on average;

3. Prognostic variables: all are three dimensional;

MA = mass (kg/m^2)

UA = eastward velocity (m/s) on C-grid

VA = northward velocity (m/s) on C-grid

H0M = mean potential enthalpy (J)

HXM, HYM, HZM = eastward, northward

and vertical gradients of potential

enthalpy (J)

Q0M = mean water vapor (kg)

QXM, QYM, QZM = eastward, northward

and vertical gradients of water

vapor (kg)

4. Parameterizations: AOM web site:

http://aom.giss.nasa.gov/DOC4X3/ATMOC4X3.TXT

a. Clouds: see AOM web site

b. Convection: see AOM web site

c. Boundary layer: see AOM web site

d. Radiation: see AOM web site;

Lacis AA, Oinas V, 1991. A description of the

correlated k distributed method for modeling

nongray gaseous absorption, thermal emission,

and multiple scattering in vertically

inhomogeneous atmospheres. JGR, 96, 9027-9063.

e. Drag at model top: a drag proportional to the square of

wind is applied to top layer velocity

components

B. Ocean

1. Resolution: 4 degrees longitude, 3 degrees latitude, up to 16

vertical layers, heat and salt have mean value

and three prognostic directional gradients inside

each cell

2. Numerical scheme: grid point model;

forward step, linear upstream shceme used

for linear advection (heat and salt);

leap frog, second order center-difference

C-grid scheme for non-linear advection

(momentum);

sigma coordinate vertical layering but

variable number of layers (consequently

each layer has approximately the same mass

per unit area in all cells);

free surface;

Bousinesq approximation not used;

freshwater fluxes change ocean mass

3. Prognostic variables: all are three dimensional;

MO = mass (kg/m^2)

UO = eastward velocity (m/s) on C-grid

VO = northward velocity (m/s) on C-grid

G0M = mean potential enthalpy (J)

GXM, GYM, GZM = eastward, northward

and vertical gradients of potential

enthalpy (J)

S0M = mean salt (kg)

SXM, SYM, SZM = eastward, northward and

vertical gradients of salt (kg)

4. Parameterizations: AOM web site:

http://aom.giss.nasa.gov/DOC4X3/ATMOC4X3.TXT

a. Eddy parameterization: none

b. Bottom boundary: bottom drag, see AOM web site

c. Mixed-layer: KPP vertical mixing scheme;

Large WG, McWilliams JC, Doney SC, 1994.

Oceanic vertical mixing: review and a model

with non-local boundary layer

parameterization. Rev. Geophys., 32, 363-403.

d. Sunlight: penetrates into top 3 layers (about 51 meters);

Paulson CA, Simpson JJ, 1977. Irradiance

measurements in the upper ocean. J. Appl.

Oceanogr., 7, 952-956.

e. Tidal mixing: none

f. River flow: enters into top ocean layer affecting mass,

mean heat, and horizontal gradients of heat

and salt

g. Isolated seas: subresolution straits connect isolated

seas to main ocean (Mediterranean Sea,

Baltic Sea, Black Sea, Red Sea, White Sea,

Persian Gulf), see AOM web site

h. North pole: treated same as in atmosphere, single vector

velocity at pole (which appears to rotate);

mass, heat and salt have same value at all

polar longitudes, GXM=GYM=SXM=SYM=0;

C. Sea Ice

1. Resolution: same as ocean (4x3), 2 mass layers, 4 thermal

layers, single ice thickness

2. Numerical scheme: velocity components defined on C-grid;

advection of ice use modified linear

upstream scheme;

call once each hour with other source terms

3. Prognostic variables: RSI = horizontal sea ice cover

RSIX,RSIY = eastward and northward

gradients of horizontal sea ice cover

MSI(2) = snow and sea ice mass (kg/m^2)

HSI(4) = heat content of layer (J/m^2)

PSI = internal sea ice pressure

USI = eastward velocity (m/s) on C-grid

VSI = northward velocity (m/s) on C-grid

4. Completeness: sea ice velocity accelerated by seven terms:

atmospheric stress, ocean drag, Coriolis and

metric term, surface pressure and ocean tilt,

internal sea ice pressure, parallel sea ice

stresses, island and coastline blocking factor;

minimum open ocean is 6% / [ice thickness (m)];

snow thicker than 91.66 (kg/m^2) is compacted

into ice

5. Salinity: none

6. Brine rejection: all salt drops into ocean when ice forms

7. North pole: velocity not defined nor used;

RSI,MSI,HSI,PSI have same value at all polar

longitudes, RSIX=RSIY=0

D. Continents: each 4x3 cell is either all ocean or all continent

1. Resolution: fixed fractions of continental cell are

ground, land ice, or lake,

ground can be partially covered by snow,

lake can be partially covered by lake ice;

ground has 4 layers plus fith layer for snow,

ground layer thicknesses: .0625, .25, 1, 4 (m);

land ice has 4 layers;

liquid lake has 2 layers,

lake ice is treated like sea ice

2. Frozen soil: each ground layer has water mass and heat

content which determines frozen fraction

3. Rivers: excess precipitation and snow melt (surface runoff)

is fed into lake in same cell;

underground runoff depends on soil types and

standard deviation of topography;

hand made river direction file:

http://aom.giss.nasa.gov/rdv4x3.html

4. Snow on ground: precipitation is uniform over a grid cell;

snow on snow-free ground adds to snow-covered

ground at rate of 21 (kg/m^2);

when snow on snow-covered ground exceeds 42

(kg/m^2) it spreads covering snow-free ground;

rain compacts some snow into ice;

if snow melts below 20 (kg/m^2), snow-covered

ground is reduced horizontally

5. Water storage: each 4 layers of ground cells have fractions

of soil types: sand, silt, clay, peat, rock;

hydraulic diffusivity depends on soil types

and liquid water availability;

water flux depends on hydraulic diffusivity,

liquid water, and air space;

evaporation from root layers 2, 3 and 4 during

growing season when sun is up, only from layer

1 othertimes

6. Albedo: determined by visible and near infrared separately;

integrated snow albedo ranges from .50 to .85

depending on thickness and age;

integrated ice albedo is .45;

integrated ground albedo depends on vegetation and

season and ranges from .50 for bright desert to .11

for rain forest

7. Vegetation: fixed fractions for 10 different types of ground

cells;

affects surface albedo, surface roughness,

evpaoration, hydraulic and thermal diffusivities,

and underground runoff

8. Prognostic variables: see

http:/aom.giss.nasa.gov/CODE4X3/C477C.S

9. Ice sheets: ice in layers 1 and 2 is 182, 3 is 910, 4 is 6370

(kg/m^2) [sums to about 8.3 (m)];

snow is distributed uniformly over land ice cell;

snow exceeding 91.66 (kg/m^2) is compacted into

ice, equal amount of ice is removed from layer 4,

and ice is then relayered;

surface melt water can refreeze in any of 4

layers, after that it seeps out into ocean via

river direction file

E. Coupling details:

1. Frequency: atmosphere and subsurface reservoirs exchange

fluxes once each hour

2. Conservation: water mass and static energy are conserved

exactly;

surface momentum stresses are conserved between

atmosphere and ocean

3. Fluxes:

a: atmo-ocean: PREC = precipitation (kg/m^2)

EPRE = energy of precipitation (J/m^2)

SRHDT = solar radiation absorbed (J/m^2)

TRHDT = thermal radiation emitted (J/m^2)

DMUA = eastward momentum stress (kg/m*s)

DMVA = northward momentum stress (kg/m*s)

W0 = dew minus evaporation (kg/m^2)

E0 = turbulent plus radiation fluxes (J/m^2)

b: atmo-land: PREC = precipitation (kg/m^2)

EPRE = energy of precipitation (J/m^2)

SRHDT = solar radiation absorbed (J/m^2)

TRHDT = thermal radiation emitted (J/m^2)

W0 = dew minus evaporation (kg/m^2)

E0 = turbulent plus radiation fluxes (J/m^2)

WR = evaporation from roots (kg/m^2)

c: land-ocean: MFLUX = mass flux from rivers (kg)

EFLUX = energy flux from rivers (J)

BERGM = ice bergs from Antarctica (kg)

BERGE = energy of ice bergs from Antarctica (J)

d: sea ice-ocean: DMOO = ice formed on open ocean (kg/m^2)

DEOO = energy of ice formation on open ocean

DMOI = ice formed beneath old ice (kg/m^2)

DEOI = energy of ice formation beneath ice

RUNS = melted surface ice (kg/m^2)

ENRG = heat from ocean to melt sea ice

DMO = ice melted at bottom of ice

DRSI = ice melted horizontally

DMUI = eastward momentum stress (kg/m*s)

DMVI = northward momentum stress (kg/m*s)

E1 = conductive energy flux (J/m^2)

e: atmo-sea ice: PREC = precipitation (kg/m^2)

EPRE = energy of precipitation (J/m^2)

SRHDT = solar radiation absorbed (J/m^2)

TRHDT = thermal radiation emitted (J/m^2)

DMUA = eastward momentum stress (kg/m*s)

DMVA = northward momentum stress (kg/m*s)

W0 = dew minus evaporation (kg/m^2)

E0 = turbulent plus radiation fluxes (J/m^2)

f: land ice-sea ice: DRSI = increase in horizontal sea ice

cover from Antarctic ice calving

HGIT = energy from Antarctic ice calving

4. Flux adjustments: no

V. Simulation Details

A. PIcntrl: 1850 to 2100

C480: B. 200-year spinup from Levitus climatological conditions

C490: B. 250-year spinup from Levitus climatological conditions

C. Monthly varying, but annually fixed, some industrial and

natural aerosols and Boucher's 1850 sulfate burden, see

solar constant is fixed at 1367 (W/m^2)

A. 20C3M: 1850 to 2000

C483: B. 200-year spinup from Levitus climatological conditions

C493: B. 250-year spinup from Levitus climatological conditions

D. Greenhouse gases: http://aom.giss.nasa.gov/IN/GHGA1B.LP ;

Boucher's time varying sulfate burden (1850 to 2000), see

http://aom.giss.nasa.gov/cp4x3in.html (#16);

other forcing agents have monthly changes, but no annual

changes

A. SRES B1: 2000 to 2100

C484: B. Initialized from end of C483

C494: B. Initialized from end of C493

D. Greenhouse gases: http://aom.giss.nasa.gov/IN/GHGB1.LP ;

Boucher's time varying sulfate burden (2000 to 2100) for

IPCC SRES B1, see

http://aom.giss.nasa.gov/cp4x3in.html (#16);

other forcing agents have monthly changes, but no annual

changes

A. SRES A1B: 2000 to 2100

C485: B. Initialized from end of C483

C495: B. Initialized from end of C493

D. Greenhouse gases: http://aom.giss.nasa.gov/IN/GHGA1B.LP ;

Boucher's time varying sulfate burden (2000 to 2100) for

IPCC SRES A1B, see

http://aom.giss.nasa.gov/cp4x3in.html (#16);

other forcing agents have monthly changes, but no annual

changes