The following User's Guide outline is contained in the README
file which is included with the model source code. It should be
sufficient to give the user enough information run the sea ice
model in conjunction with the other components of CSM (e.g.,
detailed description of the namelist variables).
1. Introduction
a. More Detailed Info
The following documentation is provided for informational purposes, and
is not intended to be complete. A description of the CSM Sea Ice Model
can be found in:
Bettge,T.W., J.W. Weatherly, W.M. Washington, D. Pollard,
B.P. Briegleb, and W. G. Strand, Jr., 1996: "The CSM
Sea Ice Model." NCAR Technical Note NCAR/TN-425+STR,
National Center for Atmospheric Research, Boulder,
Colorado.
b. Found Below
Below are several sets of notes pertinent to using the CSM Sea Ice
Model. Namely, the conceptual flowchart of the model, a description
of the namelist input variables, and a description of how the model
can be used to generate climatological sea ice as it's output to
the Flux Coupler in the event an active ice lower boundary is not
desired.
2. Conceptual Flowchart
Sea Ice Model Driver (PVM_ice_driver.F)
o read namelist input (rdnam.F)
o read land/ocean/marginal sea mask (rdsav.F)
o read the restart dataset (rdsav.F)
o initialize communication with Flux Coupler
o loop over time
* exchange information with Flux Coupler
------- * integrate ice model
| over one time period (mdlice.F)
| * write history dataset (icecdf.F)
| * write restart dataset (wrsav.F)
|
|
|
------------------
|
|
MDLICE (mdlice.F)
o prepare data for model timestep
|
|
STEPICE (stepic.F)
------- o thermodynamics
| ----- o dynamics
| | o update surface albedo
| |
| |
| ---------------------------------------
| |
THERMODYNAMICS (thermo.F) DYNAMICS (dynice.F)
o lateral ice growth o main loop over hemispheres
o lateral ice melt o iterative solution to ice
o vertical energy balance velocities (cavset.F,
model (tice3l.F *or* ticezl.F) cavit.F, icefre.F, and
icedia.F)
o advection (advect.F)
3. Namelist Input Variables
Preliminary Documentation of Sea Ice Model NAMELIST Input
---------------------------------------------------------
domain INTEGER Domain of computation. If 0, global. If
1, southern hemisphere only. If 2, northern
hemisphere only.
Example: domain = 1
Default: 0
histdump INTEGER Frequency of netCDF history dataset dumps,
keyed to day of month. If histdump=1,
dumps will be made every day (at end of
day). If histdump=10, dumps will be
made on days 10, 20, and 30 (except Feb!)
of month.
Examples: histdump = 30
histdump = 2
Default: 10
Note: The netCDF files produced will
be placed into the 'mspathw'
directory on the mass store. The
filename will be:
yyyymmdd.nc
where yyyymmdd is date. (This is
subject to change).
icemode CHAR Mode of the current ice model integration.
Must be either:
'active' - full ice computations,
including both thermodynamics
and dynamics
'sstclim' - ice is specified from SST
climatology (see namelist
input variable 'sstpath');
only thermodynamics are
performed, computing a valid
ice surface temperature
Example: icemode = 'sstclim'
Default: 'active'
ice_dynam INTEGER Ice dynamics are active if ice_dynam is
non-zero. Ice dynamics turned off if
ice_dynam is zero.
Example: ice_dynam = 0
Default: 1 (ice dynamics are ON)
idate INTEGER Date of current restart dataset. In the
form [yyyyddmm]. If a positive value,
the date on the restart dataset is ignored
and this date is used. If negative, the
date on the restart dataset is used.
Examples: idate = 19950401
idate = -1
Default: -1
locpathr CHAR Local path of input (read) restart dataset.
Limited to 56 characters. Can be an
environment variable such as '$TMPDIR'.
Example: locpathr = '$TMPDIR'
Default: '.'
monavg INTEGER Produce monthly averaged ice netCDF
history dataset. Produced if monavg
is non-zero. No data produced if
monavg is zero. If written, the
filename on the mass store is
yyyymm00.nc For example, 00411200.nc
is the average of month 12, year 41.
Example: monavg = 0
Default: 1 (monthly averages ARE produced)
msfiler CHAR Mass store file name of input (read) restart
dataset. Limited to 56 characters.
Example: msfiler = '19950901.restart'
Default: [see Example 1]
msg_group CHAR The CSS-MP (Computing Support Section -
Message Passing) message group name/id.
Limited to 56 characters.
Example: msg_group = 'The_X-Files'
Default: '$CASE'
msg_maxt INTEGER The CSS-MP (Computing Support Section -
Message Passing) message passing time-out
limit on start-up, in seconds.
Example: msg_maxt = 1313
Default: 900
mspathr CHAR Mass store path of input (read) restart
dataset. Limited to 56 characters.
Example: mspathr = '/SMITH/ice'
Default: '/$LOGNAME/$CASE/ice'
mspathw CHAR Mass store path of output (write) restart
dataset. Limited to 56 characters.
Examples: mspathw = '/SMITH/ice'
mspathw = '/SMITH/$CASE/ice'
Default: '/$LOGNAME/$CASE/ice'
nadv INTEGER Number of timesteps per model day.
Example: nadv = 12
Default: 72
naldays INTEGER Number of days to run the model in
"standalone" mode.
Example: naldays = 10
Default: 1
savretpd INTEGER Mass store retention period in days for
output (write) restart dataset. Can be as
large as 4096.
Example: savretpd = 731
Default: 367
savwcomm CHAR Mass store comment associated with output
(write) restart file. Can be as long as
56 characters.
Examples: savwcomm = ' this is nonsense '
savwcomm = ' $CASE $CASESTR '
Default: ' ' (blank)
savwpass CHAR Mass store write password associated with
output (write) restart file.
Example: savwpass = 'fgump'
Default: ' ' (blank)
safpath CHAR Full mass store directory AND file pathname
to the standalone forcing file. File will
be named locally (in pwd) as 'saf.data'.
Example: sstpath =
'/BETTGE/CSM-T01/ice/B05.30dforc.ieee'
Default: ' ' (blank)
sstpath CHAR Full mass store directory AND file pathname
to the SST climatology for use when icemode=
'sstclim'. File will be named locally (in
pwd) as 'sst.climatology'.
Example:
sstpath = '/KAUFF/DATA/sst.str.mom2x2'
Default: ' ' (blank)
The following variables MUST be specified:
None - all the defaults will suffice in simplest case,
see example 1.
Example 1:
$SEAICE
$END
In this case, the user has specified that the restart date is
as appears on the restart dataset (idate=-1). The restart
dataset will be taken for the mass store directory
/$LOGNAME/$CASE/ice ($LOGNAME will be resolved in all upper
case, and $CASE is an environment variable which MUST be set).
Under these conditions, the ice model will access and read
the mass store file /$LOGNAME/$CASE/ice/latest-restart-date,
which contains the date (yyyymmdd) of the most recent restart
dataset (this file is updated every time a restart dataset is
generated). Thus, the restart dataset is implicitly taken to
be:
/$LOGNAME/$CASE/ice/[contents of 'latest-restart-date'].restart
Also, in this case, all restart and history files will be placed
into the /$LOGNAME/$CASE/ice directory on the mass store.
This example represents a standard operating procedure during
an extended integration restart.....that is, no namelist
input needs to be updated or changed.
Example 2:
$SEAICE
, idate=19950901
, mspathr='/SMITH/CSM-xxx/ice'
, msfiler='19950901.restart'
, mspathw='/SMITH/$CASE/ice'
, savwpass='jssmith'
, savwcomm=' $CASE $CASESTR '
, savretpd=32
, icemode='active'
, histdump=10
$END
(1) The mass store restart file is /SMITH/CSM-xxx/ice/19950901.restart
(2) All restart and netcdf history files generated during the run will
be written onto the mass store in the /SMITH/$CASE/ice subdirectory.
($CASE will be resolved at run time.)
(3) Under normal circumstances, the first restart will be written at the
beginning of the next month, and will be moved to the mass store
under the pathname/filename /SMITH/CSM-xxx/ice/19951001.restart.
(4) The first history dataset generated will be placed on the mass store
under the name /SMITH/CSM-xxx/ice/19950910.nc
(6) All restart and history files written will have a password of
'jssmith', a comment ' $CASE $CASESTR ', and a retention period of
32 days on the mass store ($CASE and $CASESTR will be resolved at
run time).
4. Sea Ice Climatology Mode
The Dummy Ice Model 24 October 1995
Updated: 29 February 1996
The ice model has been set up to read a climatological SST
dataset, and produce a climatological sea ice distribution.
Use icemode='sstclim' in the namelist input.
Description:
icemode CHAR Mode of the current ice model integration.
Must be either:
'active' - full ice computations,
including both thermodynamics
and dynamics
'sstclim' - ice is specified from SST
climatology (see namelist
input variable 'sstpath');
only thermodynamics are
performed, computing a valid
ice surface temperature
Example: icemode = 'sstclim'
Default: 'active'
Details:
When icemode='sstclim' is set, the ice model performs ice
thermodynamic calculations only....returning a "valid" ice
surface temperature to the flux-coupler from computations
in tice3l.f.
When ice is determined to exist within a grid box, it's
concentration is set as described in 'ficeh' below. The
ice thickness is set to 1.0 meters, and never varies...
....it is *always* 1.0 meters, regardless of the
concentration.
Here is a list and description of the fields and fluxes
returned by the ice model to the flux-coupler during
'sstclim' integrations.....
(1) tsice ! ice/snow surface temperature (K)
a realistic value, consistent with
the same calculation made during an
'active' ice integration
(2) snowd ! snow depth on ice (m of equiv h2o)
a realistic value, calculated by
accumulating snow on top of the seaice
which has been specified by climatology;
same as active ice integration
(3) fwfice ! wtr flx at bot of ice[(kg/s)/m**2]
currently, is calculated as in 'active'
during ice growth and melt phases; however,
since no lateral melt occurs, and since the
seaice is specified as described in 'ficeh'
below, and held to a constant thickness of
1.0 meters, this term is *not* consistent
with any process occurring, and should be
*ignored*
(4) s4bot ! solar passing thru ice (W/m**2)
as with 'active' model, is computed
(5) h4 ! heat flx frm sno/ice melt (W/m**2)
since no lateral melt takes place
(ice is specified!), is zero
(6) uiceh ! eastward ice velocity (m/s)
(7) viceh ! northward ice velocity (m/s)
ice is specified, ice velocity is zero
(8) ficeh ! ice concentration on h-grid
is set as follows:
ficeh = max ( 0.0,
min(ficemax, tfreez+1.0 - SST) )
that is, ramps up linearly starting
within one degree of the freezing point
of sea water (-1.8 in the SSTs); never
greater than ficemax, which is 0.96 in
SH and 0.99 in NH (identical to 'active'
model)
(10) albsi ! ice albedo shortwave direct
(11) albli ! ice albedo longwave direct
(12) albsf ! ice albedo shortwave diffuse
(13) alblf ! ice albedo longwave diffuse
set as in active model