Re: [ferret_users] Vector EOF

[Ryo Furue <furue@xxxxxxxxxx>]

Hi Tony,

| I have been enjoyed using the EOF function of ferret recently. But now I
| need to do EOF for velocity vectors. Does anyone know how to achieve it?

As I understand (which may well be wrong), a vector EOF is to treat
each component of a vector just as an additional dimension.  Suppose
you have a 2D vector field (u(x,y,t), v(x,y,t)), you basically look
for 3D EOFs for a variable a(x,y,k,t), where a(x,y,1,t) = u(x,y,t)
and a(x,y,2,t) = v(x,y,t).

I'm not sure, but the following method may work.

If Ferret has only 2D EOF, then you can (I think) achieve the same
effect by 1) squashing the x-axis (by regridding) and remapping
the u field on to the western hemisphere, say, and v on to the eastern
hemisphere, 2) finding EOFs, and 3) "re-assembleing" the EOFs
to a vector, taking their x-components from the western hemisphere
and y-components from the eastern hemisphere.

Regards,
Ryo