directions,
around a given grid point (i,j), Gi, G j the maximum of these two gradients and n;m the number
of grid points in the east-west and south-north directions, respectively.
A perfect
match between two situations leads to S1=0 and thus the smaller S1, the better. This
score has been used by e.g. Obled et al. (2002), Wetterhall et al. (2005) and Marty et al. (2012)
with either MSLP or Z
/media/vedurstofan/utgafa/skyrslur/2014/VI_2014_006.pdf