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RE: [ferret_users] Calculating relative vorticity
Hi Ryo,
Thanks very much indeed!
Just one query, your formula for calculating relative vorticity in ferret in
fine provided we ASSUME zeta = du/dx - dv/dy. BUT I think the actual formula
for calculating relative vorticity is zeta = dv/dx - du/dy. This may lead to
slight modification to the code. Please verify.
Savin
-----Original Message-----
From: owner-ferret_users@xxxxxxxx [mailto:owner-ferret_users@xxxxxxxx] On
Behalf Of Ryo Furue
Sent: Thursday, 26 June 2008 8:05 AM
To: ferret_users@xxxxxxxx
Subject: Re: [ferret_users] Calculating relative vorticity
Hi Billy,
Thanks for your highest praise!
| Amazingly, I think Ryo is wrong about the sphere/cosine business. If
| (u,v) is given on a lat/lon grid, then Ferret will do this
| automatically.
But, I don't think Ferret distinguishes vectors from scalars
when it takes derivatives. Derivatives of vectors are different
from those of scalars. Look at my formula again:
d(u cos(phi))/dy
u[y=@DDC] would give you du/dy, which isn't what we want, right?
Or would Ferret somehow figure out that u is an x-component of
a vector and multiply the cosine factor before taking
the derivative?
Cheers,
Ryo
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