Table of Contents - The Atmospheric Studies Group at TRC

Section 7: Prognostic Meteorological Interfaces
7.4 CALRAMS Preprocessor
CALRAMS operates on the output from the NOAA Air Resources Laboratory (ARL) Regional
Atmospheric Modeling System (RAMS), Version 4.3. It extracts and reformats a subset of the gridded
model output fields, and creates a 3D.DAT file for CALMET (see section 7.5).
RAMS was developed at the Colorado State University and the *ASTeR division of Mission Research
Corporation in the 1980’s. The main goal of the modeling system is for simulating and forecasting
mesoscale meteorological fields, although it may be applied at both smaller and global scales.
Specialized studies have applied RAMS at scales as small as 1m for boundary layer simulations and flows
around individual buildings. RAMS can be initialized from NCEP model fields (Eta, AVN, NGM, etc.)
in ARL packed form. Many different spatially varying surface variables such as soil moisture, soil and
vegetation type, canopy temperature and water content, terrain height, land roughness, land percentage
and sea surface temperature (SST) are ingested into RAMS on the model grid.
The horizontal coordinate used in RAMS is the Arakawa-C staggered grid of thermodynamic and
momentum variables. The advantage of this staggered grid coordinating is to reduce finite differencing
errors. The grid configuration is shown in Figure 7-8. The momentum variables of wind U and V
components are defined at * points, while the thermodynamic variables of temperature (T), specific
humidity (Q), pressure (P) are defined at + points.
*V(I,J)
T,Q,P
U(I-1,J) * + *
U(I,J)
(I,J)
Figure 7-8:
Arakawa-C grid used in RAMS.
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