Is the 40-km MAPS generally of better quality than the RUC?
The 40km MAPS usually includes improvements more quickly than the RUC. The RUC runs slightly more reliably than the MAPS. So I would give MAPS a slight edge, but this may not be true in a given case. At NCEP, the RUC may get some observations not assimilated into the MAPS. The 40km MAPS link in the index gives some more information, as well as a change log for the 40km MAPS, so you can see what changes have been made recently. Are the mass and velocity values calculated at the same grid point location, those points defined in RUC-2 file 40kmlatlon.asc? (unlike Eta where mass and velocity are at different locations – i.e. semistaggered Arakawa E grid)? The answer is yes. The native RUC model horizontal grid is an Arakawa C grid, in which there is staggering. This is in the model itself. However, all RUC wind output, even in the hybrid-b native vertical coordinate, is unstaggered back onto the mass points. So that is what you are seeing in any output file, unstaggered winds.
