2.5 Model Input Datasets

CAM2.0.2 is a combination of atmosphere, land, ocean and sea-ice components. In what follows we discuss the input datasets required by each of these components. CSMDATA refers to the root directory where the distribution datasets have been untarred by the user.

2.5.1 Atmosphere Component Datasets

Input datasets needed for the atmospheric component provide initial state data, ozone boundary data and water vapor absorptivity/emissivity data. Only the ozone dataset contains time-variant input data which is based on a 365 day year with no leap years. All initial and boundary datasets are in NetCDF format.

In general, input dataset names follow the convention:

$<$type$>$$<$simulation date$>$$<$resolution$>$$<$Spectral truncation$>$ $<$Vertical levels$>$$<$creation date$>$ Where

• Simulation date = The specific date that the given dataset is valid for. In the case of initial condition datasets this is typically given in YYYY-MM-DD form. Datasets that are valid over a span of dates typically list the year range.
• Resolution = Number of latitudes by the number of longitudes for the grid being used (i.e. 64x128, 32x64 etcetera).
• Spectral truncation = For Spectral dynamical cores (eul or sld) the spectral truncation applied to the dataset (T42, T63 etcera). This is only given if the dataset in question has had spectral truncation applied to it.
• Vertical levels = Number of vertical levels (L26, L18 etc.)
• Creation date = The date the file was created in cYYMMDD format.

2.5.1.1 Initial Conditions Dataset

The initial conditions dataset is specified by namelist variable NCDATA. This dataset contains initial values of the prognostic variables U, V, T, Q, PS, TSICE, SNOWHICE and TS1 through TS4, the surface geo-potential field PHIS, the grid-box land fraction LANDFRAC, the land ocean transition mask LANDM, and the standard deviation of geo-potential height SGH. When running flux-coupled the fields: TSICE, SNOWHICE, LANDFRAC and TS1 through TS4 are not included on the dataset. Required initial fields are outlined in 2.5.

Table 2.5: Atmospheric Component Initial Dataset Fields

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 (Kg$_{H2O}$/Kg$_{air}$)
Single Level Fields
PHIS	$\phi_s$	Surface geo-potential (m$^{2}$/s$^{2}$)
PS	P$_{s}$	Surface pressure (Pa)
SGH	SGH	Standard deviation of geo-potential height (m)
LANDM	landm	Land Ocean transition mask: LANDM = 0 indicates ocean, LANDM = 1 indicates land, and 0 $<$ LANDM $<$ 1 indicates a transition region.
TS	T$_{s}$	Surface temperature.
TSICE	T$_{ice}$	CSIM sea-ice model snow/ice surface temperature (not stored on CCSM flux-coupled simulations).
SNOWHICE		Snow depth over ice
LANDFRAC		Land fraction
TS1, TS2, TS3, TS4	T$_{s}$	Four CSIM sea-ice subsurface temperature levels (not stored on CCSM flux-coupled simulations) (K)

At times it may be desirable to start the model from a more exact state of the atmosphere, with some of the fast processes (spin-up time $<$ 1 day) also represented on the initial conditions file. Table 2.6 lists optional fields which the model will read if they exist on the file. Fields which don't exist will be set to arbitrary values as indicated in the table:

Table 2.6: Optional Atmospheric component initial dataset fields (representing "fast" processes)

Field Name	Variable Name	Description
Multi-Level Fields
CLDLIQ	q(:,:,,ixcldliq,:)	Cloud liquid water mass mixing ratio (Kg$_{liq}$/Kg$_{air}$); set to 0. if READTRACE=.false. or field not on file
CLDICE	q(:,:,,ixcldice,:)	Cloud ice mass mixing ratio (Kg$_{ice}$/Kg$_{air}$); set to 0. if READTRACE=.false. or field not on file
CLOUD	cld	Cloud fraction ; set to 0. if field not on file
QCWAT	q$_{cwat}$	Specific humidity associated with cloud water routines ; (Kg$_{H2O}$/Kg$_{air}$); set to Q if field not on file
TCWAT	T$_{cwat}$	Temperature associated with cloud water routines ; (K); set to T if field not on file
LCWAT	lcwat	Total cloud water amount (liquid + ice) associated with cloud water routines ; (Kg$_{cwat}$/Kg$_{air}$); set to "CLDLIQ+CLDICE" if field not on file
Single-Level Fields
PBLH	pblht	PBL height (m); set to 0. if field not on file
TPERT	T$_{pert}$	Perturbation temperature (eddies in PBL) (K); set to 0. if field not on file
QPERT	q$_{pert}$	Perturbation specific humidity (eddies in PBL) (KG$_{H2O}$/KG$_{air}$); set to 0. if field not on file
TSICERAD	T $_{ice\_rad}$	Radiatively equivalent Surface T over seaice (K); set to TSICE if field not on file
TBOT	T$_{bot}$	Lowest model level temperature (K); set to T(:,plev,:) if field not on file

By default, the model periodically writes an instantaneous initial conditions file containing all the fields in Table 2.5 and Table 2.6 for possible use as initial datasets in other runs. The frequency with which these datasets are written is controlled by the namelist variable INITHIST.

Finite-volume dynamics uses the same set of prognostic variables as shown above, except that U and V are on a staggered grid and are identified with names US and VS. When running with finite-volume dynamics, the initial dataset must contain US and VS; U and V are Ignored.

All Fields are instantaneous values. In addition to the fields listed above, the initial dataset contains information on the model date, the dimensionality of the fields, the spectral truncation, and the latitudes, longitudes, and vertical levels of the data.

A T42 (64 latitudes x 128 longitudes grid resolution) 26-level initial dataset is provided with the CAM2.0.2 distribution:

CSMDATA/atm/cam2/inic/gaus/cami_0000-09-01_64x128_T42_L26_c020514.nc.

Other initial datasets at different model resolutions can also be found in the directories

CSMDATA/atm/cam2/inic/gaus

and

CSMDATA/atm/cam2/inic/fv

2.5.1.2 Ozone Dataset

The ozone boundary dataset contains ozone volume mixing ratios which are constant for a given latitude. This dataset is defined on a pressure grid (unlike the hybrid grid of the model). 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 needed for interpolation. The ozone dataset is specified by namelist variable BNDTVO. Unlike the initial conditions file, CAM is capable of interpolating the ozone dataset to any vertical and or horizontal resolution so the user need not specify new ozone datasets when changing model resolution. The default ozone dataset provided with the distribution is

CSMDATA/atm/cam2/ozone/pcmdio3.r8.64x1_L60_clim_c970515.nc.

2.5.1.3 Water vapor absorptivity/emissivity dataset

This is a lookup table for water vapor absorption. It is specified by setting the namelist variable, ABSEMS_DATA. The default dataset provided with the dataset distribution can be found in

CSMDATA/atm/cam2/rad/abs_ems_factors_fastvx.052001.nc.

2.5.1.4 Aerosol Mass dataset

[Science description if any goes here]. As of CAM2.0.2.dev40, CAM requires the input aerosol dataset to be resolution-dependent. Memory and startup CPU overheads proved to be a bottleneck in the original implementation. Now horizontal interpolation to the target CAM grid and vertical integrals are done offline. Code and README describing the procedure are in subdirectory cam/tools/interpaerosols of the CAM distribution.

CSMDATA/atm/cam2/rad/abs_ems_factors_fastvx.052001.nc.

2.5.2 Ocean Component Datasets

CAM 3.0 supports running with either a data ocean model or a prognostic slab ocean model. The data ocean model simply reads and interpolates sea surface temperature (SST) data. Running the data ocean component requires a time-variant SST dataset. The SST dataset must be at the model resolution and is specified by the namelist variable BNDTVS.

The standard SST dataset is a climatological dataset containing 12 monthly time samples. The model can also read multi-year SST datasets. If a multi-year SST dataset is used, the namelist variable, SST_CYC must be set to .false. (it's default value is .true.).

An SST dataset on a (64 X 128) Gaussian grid can be found in

CSMDATA/atm/cam2/sst/sst_HadOIBl_bc_64x128_clim_c020411.nc.

Other SST datasets, at different model resolutions, can also be found in this directory.

The slab ocean model requires that the SST dataset specified by BNDTVS contain two additional fields specifying mixed layer depths and Q-fluxes. Preparation of these special SST datasets for the slab ocean model is described in Section 2.3.2.

2.5.3 Sea-Ice Component Datasets

The sea-ice component in CAM2.0.2 is a simplified version of the CCSM CSIM4 code. This component requires ice coverage data. The ice coverage data is contained in the same file as the SST data required by the ocean component. For the standard configuration, ice-coverage data is found in

CSMDATA/atm/cam2/sst/sst_HadOIBl_bc_64x128_clim_c020411.nc.

2.5.4 Land Component Datasets

For a full discussion of CLM2.1 input datasets see the CLM2.1 User's Guide at

http://www.cgd.ucar.edu/tss/clm/distribution

CLM2.1 always requires a dataset providing plant functional type physiological constants. This dataset is specified via the CLM2.1 namelist variable FPFTCON.

A time-invariant CLM surface dataset will be generated at run time if the CLM namelist variable FSURDAT is set to blank. If this is the case, additional settings must be provided for MKSRF_FGLACIER, MKSRF_FLAI, MKSRF_FLANWAT, MKSRF_FSOICOL, MKSRF_FSOITEX, MKSRF_FURBAN, MKSRF_FVEGTYP. If a surface dataset at the model resolution already exists, then FSURDAT should be set appropriately. The default land surface dataset provided with the distribution is

CSMDATA/lnd/cam/srfdata/cam/clms_64x128_c020514.nc.

Other provided surface datasets at other model resolutions can also be found in this directory.

CLM2.1 initial conditions will be generated at run time if the CLM2.1 namelist variable FINIDAT is blank (the default setting). It is important to note that due to the differences in data structures, CLM2.1 initial datasets are not in the same form as CLM2.0 initial datasets. The directory models/lnd/clm2/tools/convert_inic contains routines needed to perform the conversion of CLM2.0 initial datasets to CLM2.1 form. The README file in that directory contains necessary information to build and utilize the conversion tool. If spun up values exist for a model run, then FINIDAT should be correspondingly set. The default initial dataset provided with the distribution is:

CSMDATA/lnd/clm2/inidat_2.1/cam/clmi_0000-09-01_64x128_T42_c021125.nc.

This initial dataset should only be used in conjunction with the default CLM2.1 surface dataset given above.