From: David Small <david.small2_at_nyahnyahspammersnyahnyah>

Date: Sat, 16 May 2009 12:04:59 -0400

Date: Sat, 16 May 2009 12:04:59 -0400

Hello everyone,

Iım trying to calculate the gradient of the geostrophic wind from ECMWF

Reanalysis on a reduced gaussian grid. To do so, Iım using the centered

finite difference routine in NCL to avoid a problem near the equator when

using the spherical harmonic routines. I have no problem when I calculate

the meridional derivative, it compares well to that which I calculated from

the 2.5 degree ECMWF on a fixed grid. The problem is with the longitudinal

derivative which is giving me junk. Does anyone have any clue what the

problem might be?

As always, thank you very much for all your help.

Dave Small

dlon = 1.125*0.0174533 ; convert to radians

dlat = dlon*6378388.0

do nl=0,72

dX = 6378388.*cos(0.0174533*lat(nl))*dlon ; constant at this latitude

v_grad_lon(:,:,nl,:) = center_finite_diff(v(:,:,nl,:), dX , True,0)

u_grad_lon(:,:,nl,:) = center_finite_diff(u(:,:,nl,:), dX , True,0)

end do

-- David Small Graduate Research Assistant Department of Atmospheric and Oceanic Sciences McGill University Montreal, Quebec, Canada

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Received on Sat May 16 2009 - 10:04:59 MDT

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