NSWRS
                                 -----

The NSWRS (net short wave flux at the surface) can be upwards (positive).
Since the surface absorbs some of the downward short wave flux, a net 
upward flux is unusual.  Of course, we could blame city lights but the 
small upward fluxes is really caused by interpolation errors.  More details 
can be found in GRID.RAD.