Certain static data bases need to be available to define the simulation domain for MM5. There are currently five resolutions of terrain data bases and three resolutions of land-use data bases that NCAR distributes to support MM5 simulations. The terrain data bases are 60-minute (1 degree or about 111 km in mid-latitudes), 30-minute (0.5-degree or about 55 km in mid-latitudes), 10-minute (about 18.5 km in mid-latitudes), 5-minute (about 9.25 km in mid-latitudes), and 1-minute (about 0.925 km in mid-latitudes). The first four terrain data bases include world-wide coverage; the 1-minute data base is currently only available for the continental U.S. The land-use data bases are available in 60-minute, 30-minute, and 10-minute resolutions for world-wide coverage. The land-use data includes 13 categories of land use, and each land-use category has a seasonally parameterized set of physical properties that are used to model physics calculations (e.g., albedo, available moisture, emissivity, roughness length, thermal inertia). The terrain and land-use data bases are available in both Cray and IEEE formats from the NCAR anonymous FTP site (ftp://ftp.ucar.edu, in directory /mesouser/Data). The terrain and land-use data are interpolated to the MM5 simulation grid in the TERRAIN program (discussed in Section 3.5.1).

The data bases are assigned to MM5 simulations based on the resolution of the simulation domain. The terrain and land-use data bases for an individual domain should be the same resolution wherever possible (e.g., do not assign a 60-minute terrain and a 30-minute land use to the same domain). Note that higher-resolution terrain and land-use data should be used for higher-resolution domains, even within the same simulation. For example, a 108-km domain may be assigned the 60-minute terrain and land use, while a 36-km nest may be assigned the 30-minute terrain and land use.