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2. Using CCM3.6

    2.3 Model Input Datasets

2.3.3 Land Surface Model Input Datasets

Table 2.10: Land Surface Model: Initial Dataset Time Invariant Fields

Field Name	Description
latixy	latitude
longxy	longitude
surf2d	surface type
soic2d	soil color
sand2d	percent sand
silt2d	percent silt
clay2d	percent clay
pctlak	percent lake
pctwet	percent wetland
drngarea	LSM grid cell areas
drngfrac	Fractional drainage matrix
drngbasn	Basin type drainage matrix

Time variant initial data fields are 1-dimensional vectors for the LSM subgrid points. The fields are summarized in the following table and are all single level except where indicated.

Table 2.11: Land Surface Model: Initial Dataset Time Variant Fields

Field Name	Description
h2osno	Snow water (KgH2O/m2)
h2ocan	Canopy water (KgH2O/m2)
h2osoi	Volumetric soil water content (mm3H2O)/(mm3soil) (multi-level) (0<=h2osoi<=watsat)
tv	Vegetation temperature (K)
tg	Ground temperature (K)
tsoi	Soil temperature (K) (multi-level)

Initial LSM data can be generated at run time or can be obtained from a previously generated LSM initial dataset (see Initial runs  in the LSM User's Guide). If LSM namelist variable FINIDAT is set to the name (or full pathname) of an LSM initial file, initial LSM data will be obtained from that file. The LSM initial dataset must, however, have the same grid resolution and number of LSM subgrid points as the run for which it is intended.

Alternatively, if FINIDAT is set to "arbitrary initialization", LSM initial data fields are computed at run time and output to file lsmi_arbini.nc.  In this case, LSM initializes the time-variant initial fields to reasonable values (but which are not in equilibrium with the atmosphere).  Six additional datasets independent of the LSM grid resolution are also required. These files are summarized below:

Table 2.12: Land Surface Model: Resolution Independent Datasets

Dataset	Description
olson.data	land type data on 1/2 x 1/2 degree grid (ASCII format)
bats.data	soil color data on T42 gaussian grid (ASCII format)
webb.1x1	soil texture data on 1x1 degree grid (ASCII format)
flak.1x1	inland water data on 1x1 degree grid (ASCII format)
swmp.1x1	swamp data on 1x1 degree grid (ASCII format)
drainage.p5xp5.nc	drainage data on 1/2x1/2 degree grid (netCDF format)

LSM initial datasets are simply instantaneous LSM netCDF history files containing the fields necessary for initialization. During a model run, they can be generated monthly, yearly or not at all depending on the value of the LSM namelist variable INITHIST. LSM initial datasets produced during a model run have the names lsmi_yyyymmdd_sssss.nc where yyyy is the year, mm is the month, dd is the day, and sssss is the seconds into the day of the simulation.

When the LSM attempts to acquire input data files, it first looks in the current working directory (i.e. the model executable directory). If the required files are not there, the directory specified by the LSM namelist variable, DATADIR, is searched. If the files are still not found, it looks for the full pathname of the file, first on disk and then on the MSS (Mass Storage System). Note that if the LSM initial data is created at run time, the six additional input datasets must either be in the model executable directory or in the directory specified by DATADIR.

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Questions on these pages can be sent to... erik@ucar.edu .