In connection with the JRodos near range ADMs, three spatial grids play a role:
The numerical weather data from national or global weather services have some fixed inner spatial resolution. For example, the global meteorological weather prediction (NWP) data from the American NOMAD Server in Grib1 format have a 1 degree resolution, ⇔ 100 km pixel size, and the Grib2 data 0.5 degree ⇔ 50 km pixel size.
The JRodos meteorological pre-processor derives from these input data all meteorological parameters relevant for the near range atmospheric dispersion and deposition calculations, such as the boundary layer conditions and wind vectors. This is done on an grid with 200 x 200 equidistant points covering the area of interest (100 x 100 points in the versions before March 2014). For a rectangular grid extending to a distance of 100 km from the release point, this achieves a spatial resolution of 1000 m. For the JRodos near range atmospheric transport and deposition calculations, a telescopic grid is used , for example the JRodos New Grid shown in the Figures below, with about 8000 grid cells and five rings with decreasing resolution from the inner to the outer ring. The resolution of the innermost ring determines the calculation distance, for example, 100 km for an inner spatial resolution of 250 m.
Rimpuff, Atstep and Dipcot solve the advection-dispersion equations in the center points of the cells of the telescopic grid, using the meteorological parameters of the corresponding meteorological pre-processor grid cells.
With LASAT, however, the determination of the meteorological parameters and the dispersion calculations are performed on the same grid. This is achieved by running the meteorological pre-processor separately for each spatial resolution of the telescopic grid, up to the distance covered by the respective telescopic grid part, that is, five times for five resolution steps of the JRodos New Grid (“five-fold nesting”).