Table of Contents - The Atmospheric Studies Group at TRC

Section 7: Prognostic Meteorological Interfaces
The vertical coordinate is the terrain-following height Z* system, with Z* is defined as
Zagl
Z*
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Zterr
1
Ztop
where Z agl is the height above the ground, the Z terr is the topographical height at grid, and Z top is the height
of model top. In this coordinate system, each level is a given fraction of the distance between the surface
and the model top. The variables are staggered in vertical. The horizontal momentum of U and V
components and all thermodynamic variables are defined at the full Z* levels, while the vertical velocity
(W) is defined at half-Z* levels. The model top height is usually about 15-20 km above the ground.
The 3D.DAT file for CALMET needs a uniform coordinate system in both horizontal and vertical
directions. Since most variables are at thermodynamic points, a two-grid averaging is used to interpolate
momentum variables of U, V, and W in the staggered Arakawa-C coordinate system to its thermodynamic
point. The set of thermodynamic point coordinates is used in the 3D.DAT file.
The CALRAMS processor runs on a UNIX platform and includes a host program called CALRAMS.F90
and a set of subroutines that perform various functions.
CALRAMS Input Files
RAMS Output file
CALRAMS was designed for a particular application of RAMS, with specific file names. Each RAMS
file consists of one hour of model output for one nest. The naming convention is:
iw-A-YYYY-MM-DD-HH0000-g1.vfm
iw-A-YYYY-MM-DD-HH0000-g2.vfm
iw-A-YYYY-MM-DD-HH0000-g3.vfm
iw-A-YYYY-MM-DD-HH0000-g4.vfm
iw-A-YYYY-MM-DD-HH0000-head.txt
where YYYY is the 4-digit year, MM is the 2-digit month, DD is the 2-digit day, and HH is the 2-digit
hour. The file with “head.txt” is the header file providing the RAMS configuration and output variables.
The part “-g1 –g2 –g3 –g4” represents the nesting levels for the output. Because many hours are typically
processed in one simulation, creating a 3D.DAT file requires many RAMS files. These file names are
constructed by CALRAMS for the processing period, so all RAMS files for the period must reside in a
single directory. Applications that use different file names will require changes to the CALRAMS code.
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