air quality assessment & management
Reference and User Manual
AirWare   On-line Reference Manual
  Release Level 7.0
  Revision Level beta
  Release Date 2015 03

Last modified on:   Thursday, 16-Jul-15 09:25 CEST
MM5 Meteorological Model

Dynamic 3D meteorological data are calculated using PSU/NCAR mesoscale model (known as MM5). MM5 is a limited-area, nonhydrostatic, terrain-following sigma-coordinate model designed to simulate or predict mesoscale atmospheric circulation. The model is supported by several pre- and post-processing programs, which are referred to collectively as the MM5 modeling system.

The MM5 modeling system software is mostly written in Fortran, and has been developed at Penn State and NCAR as a community mesoscale model with contributions from users worldwide. (Reference:

Model implementation:

MM5 is implemented for a pre-defined domain covering an area large enough to account for the air flow during the 48 hour simulation period. The model uses two-way nesting between mother domain at a coarse resolution (~ 27 km) and nested domains at finer resolutions (up to ~3 km). The nesting ratio is always 3:1 for two-way interaction, meaning that the nest's input from the coarse mesh comes via its boundaries, while the feedback to the coarser mesh occurs over the nest interior.

Model structure:

    TERRAIN - calculates model horizonatal grid
    REGRID/pregrid - reads global input data
    REGRID/regridder - interpolates input data on horizontal grid
    INTERPF - interpolates input data on vertical grid
    MM5 - main directory with model physics
    MM5/Run - model run
    OUTPUT - output directory
    MM5toCAMx - conversion from MM5 output to CAMx input

Initial conditions and forcing: In MM5 all four boundaries have specified horizontal winds, temperature, pressure and moisture fields. The boundary values come from analyses at the future times from another model's forecast (in real-time forecasts). For real-time forecasts the lateral boundaries depend on a global-model forecast. In studies of past cases the analyses providing the boundary conditions may be enhanced by observation analysis.

The model uses these discrete-time analyses by linearly interpolating them in time to the model time. The analyses completely specify the behavior of the outer row and column of the model grid. In the next four rows and columns in from the boundary, the model is nudged towards the analyses, and there is also a smoothing term. The strength of this nudging decreases linearly away from the boundaries. To apply this condition, the model uses a boundary file with information for the five points nearest each of the four boundaries at each boundary time.

Minimum requirement to run MM5 model is a gridded atmospheric data that have at least these variables: sea-level pressure, wind, temperature, relative humidity and geopotential height; and at these pressure levels: surface, 1000, 850, 700, 500, 400, 300, 250, 200, 150, 100 mb;


MM5 in AirWare generates optional dynamic Meteorology Scenarios for CAMx (see also: MM5 to CAMX coupling), and in principle also for other models such as AERMOD, PBM or PUFF. The scenarios can be in sopport of schedules runs (hourly nowcasts of 24/48 hour forecasts), or for scenario of historal events/periods (24 hours).

MM5 also provides input for the DUST emission model for "natural" dust (wind erosion of soils, re-entrainment). The MM5 data input is described in DUST: meteo data ionput.

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