Traditional TM3 Grids
Traditionally, the TM3 atmospheric transport model has a global regular lat-lon grid of size im*jm.
The grid cell centers are at
lon(i) = -180.+(i-1)*360./ im
lat(j) = -90.+(j-1)*180./(jm-1)
Note two peculiarities:
- The longitude coordinates start with a grid cell center at -180° (not with a boundary at -180°).
- The South and Nord poles are represented by one circumpolar grid cell only,
representing the sum (or average, respectively) over all longitudes.
The values for these cells are located at field indices (1,1) and (1,jm), respectively;
all cells (2:im,1) and (2:im,jm) are undefined and not used.
The latitudinal extension of the polar cells is only half of that of the normal grid cells,
leading to the latitudinal grid spacing of 180./(jm-1).
There are several standard grid sizes:
| Grid tag
| Size (im*jm)
| Resolution (ΔLon x ΔLat)
|
| cg
| 36*24
| ~10° x 8°
|
| fg
| 72*48
| ~5° x 4°
|
| vfg
| 192*96
| ~1.8° x 1.8°
|
| xfg
| 320*161
| ~1.1° x 1.2°
|