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Description of RAMS

GENERAL

The Regional Atmospheric Modeling System (RAMS) developed at Colorado State University utilizes the full set of nonhydrostatic, Reynold's averaged primitive equations (Tripoli and Cotton, 1986). The model solution is advanced in time using a hybrid timestep scheme in which the momentum and scalar fields are integrated using a second-order accurate leapfrog and forward scheme respectively. RAMS uses the staggered C grid (Mesinger and Arakawa, 1976) adn a terrain-following sigma-z coordinate scheme in the vertical (Gal-Chen and Somerville, 1975; Clark, 1977; Tripoli and Cotton, 1982). Numerous options for the boundary conditions, turbulence parameterization, radiation schemes, microphysical parameterizations, and surface schemes are available. For a more general discussion of the numerous options available in the model, users are referred to Pielke et al. (1992) and Cotton et al. (2001). In addition, the RAMS code is currently owned by ATMET (ATmospheric, Meteorological and Environmental Technologies)

The options specific to the forecast model configuration are described below.

FORECAST MODEL CONFIGURATION

GRIDS
Number: 3

Horizntal Grid Spacing:
Grid 1: 48 km
Grid 2: 12 km
Grid 3: 3 km

Vertical Grid Spacing:
35 levels Variable spacing with finest resolution in the lowest levels
Model Top: ~19 km

TIMESTEP
Grid 1: 60 sec
Grid 2: 20 sec
Grid 3: 6.667 sec

DURATION OF SIMULTION
48 hours

INITIALIZATION
80 km Eta data

BOUNDARY CONDITIONS
Radiative lateral boundary conditions (Klemp and Wilhelmson, 1978)

RADIATION SCHEME
Two-stream radiation parameterization (Harrington, 1997; Harrington et al., 1999)

SURFACE PARAMETERIZATION
LEAF2 (Walko et al., 2000)

TURBULENCE SCHEME
Mellor and Yamada (1974, 1982) (employs prognostic TKE)

MICROPHYSICS PARAMETERIZATION
Single-moment bulk microphysics (Walko et al., 1995)
Species activated:

- cloud water
- rain
- pristine ice
- snow
- aggregates
- graupel
- hail

Official documentation for RAMS can be found here.




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