The NARAC's Grid Generator (GridGen) software generates variable resolution grids for ADAPT and LODI simulations (see figure). Different grids may be used for the meteorological fields produced by ADAPT and the concentration fields output by LODI. Variable-resolution model grids provide more accurate higher-resolution simulations in critical areas of interest, such as locations near the release site and in the atmospheric boundary layer that borders the ground surface. GridGen also supports the use of nested meteorological grids.
ADAPT/LODI grids are relocatable and scaled for use anywhere in the world. Local, regional, or hemispheric grids can be defined on the map projection appropriate to the size and location of the simulation (e.g., Universal Transverse Mercator, Lambert Conformal Conic, and Polar Stereographic). System elevation databases provide topographical data that is used to determine a continuous terrain-following lower boundary.
GridGen also is used to describe the grids on which both external and in-house numerical weather prediction model output is provided. Other grids define the region and resolution for extraction of additional information from system databases that is needed as input to the models or for the generation of NARAC products (e.g., land-use characteristics or population).