# Re: rotation of wind components ...

From: Dennis Shea <shea_at_nyahnyahspammersnyahnyah>
Date: Thu Oct 27 2011 - 10:10:58 MDT

I speculate that the wind components are earth referenced
and not map referenced. They are just on a Lambert Conformal projection.

If not, u and v must be rotated together. Actually, *any* vector pair
must be rotated together. However, almost all interpolation methods
ignore this. Something like,

uNew = u*cos(rot) - v*sin(rot)
vNew = u*sin(rot) + v*cos(rot)

Of course, you must provide the rotation angle (rot)

[NCL's spherical harmonic regrid functions are an exception. Actually,
they calculate vorticity and divergence; interpolate theses scalar
quantities; then, derive the rotational and divergent wind components]

D

On 10/27/11 4:37 AM, Ufuk Utku Turuncoglu (BE) wrote:
> Hi,
>
> I have wind components (u and v) in model grid which is in Lambert
> Conformal projection. So, it means that it is rotated. I just want to
> get unrotated wind components (earth-oriented). How can i do it? I think
> that interpolation form curvilinear grid (Lambert Conformal) to regular
> lat-lon grid solves the problem but i just wonder that is there any way
> to do it inside of the NCL.
>
> Best regards,
>
> --ufuk
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Received on Thu Oct 27 10:11:06 2011

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