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2.3 Model Input Datasets
CCM3.6 is a combination of atmosphere, land, and ocean components. Input
datasets needed for the atmospheric component define initial state and
ozone boundary data. The land component requires initial state data over
land only. If the ocean component is run as a slab ocean model (SOM) it
requires initial state and boundary data, whereas if it is run as a data
ocean model (DOM), it requires SST input data. The default ocean configuration
is the data ocean model. All initial state and boundary data are in netCDF
format. All time-varying input datasets (e.g. ozone boundary dataset) are
based on 365 days per year with no leap years.
Initial and ozone boundary data for the atmosphere component is specified
via the CCMEXP namelist variables NCDATA and BNDTVO,
respectively. The ocean boundary dataset is specified via the CCMEXP
namelist variable BNDTVS. Finally, the initial land dataset is
obtained from the LSMEXP namelist variable FINIDAT. Initial
state data are only provided at T42 resolution.
See "Obtaining the Source Code and
Datasets" for information describing how to obtain these datasets.
2.3.1 Atmosphere Component Datasets
The atmospheric component requires initial conditions and ozone datasets.
2.3.1.1 Initial Conditions Dataset
The, initial conditions, dataset is specified by namelist variable NCDATA.
This dataset contains initial values of prognostic variables (U,V,T,Q,PS,
and TS1 through TS4), the surface geopotential field
(PHIS), the orography flag (ORO), and the standard deviation
of geopotential height (SGH). Required initial fields are outlined
in the table below. By default, the model writes an instantaneous
history file containing these fields each simulated month (controlled by
namelist variable INITHIST) for possible use as an initial dataset
in another run. In order to use one of these files as an initial
dataset, the utility ccm2nc
must first be run to convert it to netCDF format.
Table 2.7: Atmospheric Component Initial Dataset
Fields
|
History file
Field Name
|
Variable Name
|
Description
|
|
Multi-Level Fields
|
| T |
T |
temperature (K) |
| U |
u |
zonal wind component (m/sec) |
| V |
v |
meridional wind component (m/sec) |
| Q |
q |
water vapor specific humidity
(KgH2O/Kgair) |
|
Single Level Fields
|
| PHIS |
 |
surface geopotential (m2/s2) |
| PS |
Ps |
surface pressure (Pa) |
| SGH |
SGH |
standard deviation of geopotential height (m) |
| ORO |
ORO |
surface type flag:
= 0 over ocean
= 1 over land
= 2 over sea ice |
| TS1,TS2,TS3,TS4 |
Ts |
Four subsurface temperature
levels (K)
(TS1 is surface temperature) |
All fields are instantaneous values. In addition to the prognostic
fields, the initial dataset contains information on the time for which
the data are valid, the dimensionality of the fields, the spectral truncation,
and the latitudes, longitudes, and vertical levels of the data.
When running with the SOM, the standard initial dataset is replaced
by a SOM initial dataset. In addition to the initial fields shown above,
the SOM initial dataset requires a sea ice thickness (SICTHK)
and snow cover (SNOWH) to initialize the ice component of SOM
as shown below.
Table 2.8: Additional Slab Ocean Model Initial
Dataset Fields
|
History file
Field Name
|
Variable Name
|
Description
|
|
Single Level Fields
|
| SICTHK |
hi |
sea ice thickness (m) |
| SNOWH |
hs |
Snow cover (liquid water equivalent) (m) |
An 18-level initial dataset on a, 128 X 64, transform grid (T42) is
provided with the CCM3.6 dataset tar file.
2.3.1.2 Producing Initial Condition Datasets at Various Resolutions
In order to run the model at other horizontal or vertical resolutions,
utility programs have been included to create an, initial conditions, file
at whatever resolution the user wishes. Directory ccm/tools/interpic
(created when untarring ccm3.6.code.tar) contains code to interpolate
a netCDF format CCM3 history file to a 3-D grid specified by command-line
arguments. If a horizontal interpolation is performed (by specification
of -x and/or -y command line arguments) the required input
field ORO will not be produced on the output file. Otherwise,
ORO will be produced. ORO is a land/ocean/sea-ice discrete flag field
for which horizontal interpolation would be meaningless. For the
case where ORO is not produced, the user must then refer to directory
ccm/tools/definesurf . This directory contains code to read
a high-resolution topography dataset and produce the required input
fields SGH, PHIS, and ORO on an existing CCM3 history file in netCDF format.
The high resolution topography dataset is named topo.nc and is
included with the standard CCM datasets tar file. The user is referred
to README files in the above directories for further information and specific
instructions on how to build and run these utilities. An example
sequence of commands to produce a horizontally interpolated T21 initial
dataset would be:
interpic -x 64 -y 32 SEP1.T42.0198.nc
SEP1.T21.nc
definesurf -t topo.nc SEP1.T21.nc
Because of the horizontal interpolation from T42 to T21,
both of the above commands are required and must be run in
the indicated sequence for a complete initial dataset to be produced.
interpic interpolates the initial prognostic fields and definesurf
creates the T21 ORO field from the high resolution topography.
2.3.1.3 Ozone Dataset
The ozone boundary dataset contains ozone volume mixing ratios. These values
are interpolated to the model vertical levels at each model grid point.
The ozone dataset is in netCDF format and contains the fields PS and
OZONE . PS is a constant 1000 mb pressure field.
The ozone dataset is specified by namelist variable BNDTVO.
Sub Sections
-
2.3.1 Atmosphere Component Datasets
-
-
2.3.2 Ocean Component Datasets
-
-
2.3.3 Land Surface Model Input Datasets
-
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Questions on these pages can be sent to...
erik@ucar.edu .
$Name: ccm3_6_6_latest2 $ $Revision: 1.44.2.1 $ $Date: 1999/03/25 21:38:04 $ $Author: erik $