[ferret_users] how to extract 2D subgrid variance?

[Lev Tarasov <lev@xxxxxx>]

Hi all;
	At times I need to extract the subgrid variance of a bed 
topography, and I've been using:
let hbvar=HBG[gx=XLONGRF5@var,gy=YLATGRF25@var]
! HBG is from a higher resolution data set

but have just noted (from some explicit checking and then rechecking the 
ferret docs):

Note: This transformation is suitable for regridding only in a single 
axis. When applied simultaneously to two axes, for example, it will 
compute the variance of the variance. For example, V[gx=130E:80W:10@VAR, 
gy=205:20W:10@VAR] is equivalent to tmp[X=130E:80W:10@VAR] where 
tmp=V[y=20S:20N:10@VAR].

So how can I regrid/extract the 2D subgrid variance?

Cheers,

lev

Lev Tarasov -   Dept of Physics and Physical Oceanography,
		Memorial University of Newfoundland.
                email: lev@xxxxxx
                http://www.physics.mun.ca/~lev/
		Tel (709)-864-2675
		Fax (709)-864-8739