Weather models

MM5 model at NCMRWF

MM5 meso-scale model implemented at National Center for Medium Range Forecasting Center (NCMRWF) is version 3.6, NCAR, 2002 model for weather forecasting services. It is a non-hydrostatic model with prognostic equations like U, V, T, q, Ps with optional parameters like Total Kinetic Energy, rain, cloud water, snow, ice, hail. It works on semi-implicit time integration and two way nesting. The boundary conditions for the model are nested and time dependent, upper radiation condition and inflow-outflow relaxation. The model also considers fourth order horizontal diffusion for inner domains and second order horizontal diffusion for coarser domains. Initial and later boundary conditions are provided by the surface and upper air analysis from the NCMRWF global model. Boundary conditions are updated every 12 hours.

The following are the description of the model and physics involved:

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

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

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

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

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)

Physics:

1. Cumulus Parameterization

Grell (Simplified Arakawa-Schubert)

2. PBL Parameterization

MRF PBL

 3. Explicit Moisture Schemes

Simple Ice (Dudhia)

4. Radiation Scheme

Simple cooling

5. Land Surface Processes

Five layer soil model

Description of T-80 global model implemented at NCMRWF

Model Elements	Components	Specifications
GRID	Horizontal Vertical Topography Prognostication Variables	Global Spectral-T80 (~1.4 x 1.4 Degree) 18 Sigma Layers ( .995, .981, .96, .92, .856, .777, .688, .594, .497, .425, .375, .325, .275, .225, .175, .124, .074, .021) Mean Rel. Vort., Div., Virt. Temp., Log of Surf Pres., Wat Vap. Mix ratio
DYNAMICS	Horizontal Transfer Vertical Difference Time Difference Time Filtering Horizon. Diffusion	Orszag’s Technique Arakawa’s Energy conserving scheme Semi-Implicit, 900 sec Robert’s Method Second order over quasi-pressure surface, scale selective
PHYSICS	Surface Fluxes Turbulent. Diffusion. Radiation Deep convection Shallow Convection. Large-scale convection. Clouds Rain evaporation. Land surface Processes. Air-Sea Interaction.	Monin-Obukhov Similarity Non-Local Closure SW- Lacis & Hansen, Harshbhardhan; LW- Fels & Schwarzkopf Kuo scheme modified Tiedtke’s Scheme Manabe’s Scheme Slingo’s Scheme Kessler’s Scheme Pan’s (3-Layer Soil Temp, Bucket Hydro. for Soil Moisture) Roughness length (Charnock), Obs. SST, SH & LH (Bulk Form.)