the PMIP models (Bonfils et al. 1998)
PMIP Documentation for CLIMBER-2
CLIMate and BiosphERe groupe-Climate
System Department - Potsdam Institute for Climate Impact Research : Model
PIK CLIMBER-2 (7x18) 1998
Andrey Ganopolski, PIK, PO BOX 60 12 03, D-14412 Potsdam, Germany, Phone
: +49-331 288 2594; Fax : +49-331 288 2695; e-mail : Andrey.Ganopolski@pik-potsdam.de,
Martin Claussen, PIK, PO BOX 60 12 03, D-14412 Potsdam, Germany; Phone
: : +49-331 288 2522; Fax : +49-331 288 2600; e-mail : Martin.Claussen@pik-potsdam.de,
World Wide Web URL: http://www.pik-potsdam.de.
PIK CLIMBER-2 (7x18) 1998.
Model Identification for PMIP
0fix, 6fix, 0cal, 21fix
Number of days in each month: 30 30 30 30 30 30 30 30 30 30 30 30
Petoukhov, V., A. Ganopolski, V. Brovkin, M. Claussen, A. Eliseev, C. Kubatzki,
S. Rahmstorf, CLIMBER-2 : A climate model of intermediate complexity. Part
I : Model description and performance for present climate, Clim. Dyn.,
submitted (already published as PIK-report).
Ganopolski, A. , S. Rahmstorf, V. Petoukhov, M. Claussen, 1998 : Simulation
of modern and glacial climates with a coupled global model of intermediate
complexity, Nature, 391, 351-356.
Regular spherical grid, 10x51 degrees latitude-longitude.
From the surface to the top of the atmosphere.
Different for different processes (vertically integrated thermodynamics,
10 levels dynamis, 16 levels radiative sheme).
IBM SP2 / AIX.
2 model-years per minute.
Isothermal atmosphere, no snow, saturated soil.
Time Integration Scheme(s)
Explicit time scheme, one day time step for dynamics and surface processes,
five days for radiative schemes.
Smoothing of some dynamical fields, correction of global averaged sea level
Statistical-dynamics approach. Large-scale atmospheric dynamics are described
in stationary approximation. Sea level pressure is represented as a sum
of zonally averaged and azonal component, computed separately. Pronostic
equations for vertically integrated temperature and specific humidity.
Solar constant (1 365 W/m2) and orbital parameters are calculated after
PMIP recommendations. No diurnal cycle.
Radiative active gases : CO2 (200 ppm for 21 ky BP, 280 ppm for 6 ky BP),
fixed ozone concentration.
Shortwave radiation is divided into two subintervals : ultraviolet + visible
and near infrared. The radiative scheme accounts for water vapor, aerosols,
and ozone (Feigelson et al., 1975).
Longwave radiation is based on a two-stream approximation, it accounts
for water vapor and carbon dioxide. Energy fluxes are calculated using
the integral transmission functions based on the Curtis-Godson approximation(Feigelson
et al., 1975).
One layer effective cumulus and stratus cloudiness (randomly overlapped)
with prescribed optical properties of aerosol in shortwave radiation is
taken from A. A. Lacis and J. E. Hansen (1974).
Convection is treated as in Hansen et al. (1983).
One layer effective stratiform cloudiness. Cloud amount depends on relative
humidity and vertical velocity at cloud base height. The height of cloud
layer is a fonction of planetary boundary layer height, height of tropopause,
and vertical velocity.
The fraction of cumulus cloudiness is a function of surface specific
humidity, temperature, and vertical velocity.
Precipitation is function of total atmospheric water content and cloud
Planetary Boundary Layer
The PBL is described using the modified Ekman formulation of Taylor which
includes a spiral layer above a surface layer (Hansen et al., 1983).
Very schematic orography is prescribed in the model to represent Tibetan
plateau and the high Antartic elevation. Fraction of ocean is prescribes
for every grid cell.
For control and 6fix experiment, SST and sea-ice prescribed at the present-day
climatological values. For 21cal, prescribed present-day oceani heat flux.
In control and 6fix experiment, climatological sea-ice thickness and fraction
are prescribed. In 21cal sea-ice thickness and fraction are calculated
using a simple thermodynamic model. Surface temperature is calculated from
energy balance. Effect of snow is not taken into consideration.
The fraction of precipitation in the form of snow is a function of air-temperature.
Fraction of snow is a function of temperature and snow thickness. Constant
snow density. Influence of sublimation is neglected. Surface temperature
and melting rate are defined from surface energy balance.
Land-surface scheme is based on BATS (Dickinson et al., 1986).
Six surface types : ocean, sea-ice, trees, grass, bare soil, glaciers.
Model employs two vegetation types (trees end grass), for each grid-cell
fraction of each and maximum LAI are prescribed corresponding to potential
vegetation for present-day climate (Brovkin et al., 1997).
Two soil types, distinguished only in albedo.
For each surface type roughness length is prescribed (and modified in
the case of snow) and albedo is calculated seperately for snow-free and
snow-covered conditiond. For vegetation minimum stomatal resistance and
distribution of roots is prescribed following BATS.
Surface solar absorption is determined by surface albedos. Longwave emissivity
is set to be 1.0. The surface turbulent fluxes of heat and moisture are
formulated in terms of bulk formulas with stability-dependent grag/transfer
coefficient. Over vegetated land, transpiration is calculated following
Land Surface Processes
Surface temperature is computed from energy balance. The heat conductivity
in soil is neglected. Two-layer pronostic soil moisture model accounts
for surface and sub-surface runoff and draiage . Both precipitation and
snow-melt contribute to soil moisture.
Last update November 9, 1998. For further information, contact: Céline