[ncl-talk] winds remapped to lambert projection grid

[Ming Chen]

Hi, Dennis,

Thank you for the detailed explanation.

Ming

On 11/1/19 10:51 AM, Dennis Shea wrote:
> Generally, for visual purposes, people ignore the fact that a new grid 
> location would technically require a rotation [rot] of the 
> interpolated u,v:
>
>     U =  ui*cos(rot) + vi*sin(rot)    ; ui,vi are interpolated values
>     V = -ui*sin(rot)  + vi*cos(rot)   ; U,V are after rotation
>
> Generally, the new grid is of about the same resolution so the 
> rotation angle is 'small'.
> --
> If deemed essential, it may be best to
> [a] compute the scalar quantities vorticity and divergence on the 
> source grid;
> [b] interpolate the scalar quantities to the new grdi;
> [c] derive the rotational [Ur, Vr] and divergent [Ud, Vd] wind 
> components;
> [d] combine derived components.
>
>     [Ur, Vr]  <=== derive from interpolated vorticity
>     [Ud,Vd] <=== derive from interpolated divergence
>
>     U = Ur + Ud
>     V = Vr + Vd
>
>
>
> On Fri, Nov 1, 2019 at 9:22 AM Ming Chen via ncl-talk 
> <ncl-talk at ucar.edu <mailto:ncl-talk at ucar.edu>> wrote:
>
>     Hi,
>
>     If I remapp winds on regular lat/lon grids to lambert projection
>     grids,
>     the U and V components on the lambert projection grid should be
>     grid-relative or they still remain earth-relative?
>
>     Thanks.
>
>     Ming
>
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