Description of the MM5 Mesoscale Model

As implemented at NCMRWF

(Version 3.6: December, 2002 , NCAR)

Domain:

· Horizontal (Triple Nested), see Figure.

Ø Outer Domain-1 (39 E – 121 E, 11 S – 51 N) at 90 km resolution

Ø Middle Domain-2 (64 E – 100 E, 4 N – 45 N) at 30 km resolution

Ø Inner Domain-3 (73 E – 83 E, 32 N – 40 N) at 10 km resolution

Ø Inner Domain-4 (84.1 E - 91.1 E, 19.9 N - 26.2 N) at 10 km resolution

Ø Staggered Arakawa B-Grid

· Vertical: 23 Levels (Sigma-Hybrid), Being increased to 42

· Time Steps: Domain-1: 270 S, Domain-2: 90 S, Domain-3: 30 S

· Topography: USGS (Interpolated depending on resolution)

· Vegetation/ Land use: 25 Categories (USGS)

Dynamics:

· Non-Hydrostatic

· Two-way Nesting

· Prognostic Equations: U, V, T, q, Ps, (Optional: TKE, cloud water, rain, ice, snow, graupel/ hail)

· Time Integration: Semi-implicit

· Boundary Conditions

Ø Time-dependent / Nest

Ø Relaxation/ inflow-outflow

Ø Upper Radiative Condition

· Horizontal Diffusion

Ø Fourth order for inner domains

Ø Second order for the coarser domain

· Four Dimensional Data Assimilation

(To be implemented shortly)

Physics:

· Cumulus Parameterization

Ø Grell (Simplified Arakawa-Schubert)

· PBL Parameterization

Ø MRF PBL

· Explicit Moisture Schemes

Ø Simple Ice (Dudhia)

· Radiation Scheme

Ø Simple cooling

· Land Surface Processes

Ø Five layer soil model

Initial and later boundary conditions are provided by the surface and upper air analysis fields from the NCMRWF global model. Boundary conditions are updated every 12 hours.