Abstract:
CCSM coupled model is based on a framework which divides the complete climate
system into component models connected by a coupler. This design requires four
component models -- atmosphere, sea-ice, land, and ocean -- each connected to
the Coupler, and each exchanging data with the Coupler only.
The latm6 Observational Data Atmosphere Model functions as the atmosphere
component in a CCSM
... configuration. The latm6 atmosphere component interacts
with the Coupler just like any atmosphere model would, but it is not an active
model, rather, it takes atmosphere data from input data files and sends it to
the Coupler, ignoring any forcing data received from the Coupler. Typically the
input data files contain climatological or time averaged observational data,
although some data fabrication is usually necessary as it's unlikely that real
world observations exists for all the required fields. Such a "dummy"
atmosphere model is useful for doing ocean + ice spinup runs.
This latm code is a variant of the datm code, the difference being that the
datm cycles thru daily average data fields normally created by the CCSM active
atmosphere component (CCM, now called CAM), while the latm6 cycles thru data
from other sources (for example NCEP). The latm cycles thru separate data file
streams for atmospheric states, precipitation, and radiation. Further, these
three data streams can have different sampling intervals, for example,
radiation data can be daily average data while precipitation data is monthly
average data.
The CCSM Observational Data Atmosphere Model, version 6.0 (latm6), was released
in June 2004, as part of the CCSM3.0 release.
http://www.ccsm.ucar.edu/models/ccsm3.0/datm6/ 
