[ncl-talk] winds remapped to lambert projection grid

[Dennis Shea]

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>
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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