All:
I am looking for some hints on how to solve the following problem
without using 2 for loops in NCL.
The problem is I am trying to interpolate 3D gridded data fld to a
radar conical surface. I simply want the xy grid to remain the same,
but
to interpolate to that 2D plane given by some elevation angle and
distance from the radar.
So I have a scalar 3D field like reflectivity
dbz(z,y,x)
which has xg, yg, and zg grid dimensions (each are 1D).
and I have a 2D field of heights created from knowing where each xy
grid pt is and computing the distance from the radar so that
zhgt(y,x) = distance_from_radar * tan(elevation_angle).
So at each x,y point, I need to search for the correct height point
near zhgt(y,x) and then do a simple linear interpolation.
The dumb way would be (forgive the bad syntax)
for j = 0,ny-1
for i = 0,nx-1
k = (search for vertical grid pt right below zhgt(j,i))
uzinterp = coeff * dbz(k,j,i) + (1-coefff)*dbz(k+1,j,i)
end for
end for
But I will bet for a 200x200 (or larger grid) this will be slow!
I am pretty sure that I can easily create a 2D array of the vertical
index "k"
k_2d = ind(zg .le. zhgt) ????
but how can I select the 2D set of points in the dbz(z,y,x) that are
given by k_2d? is there some fancy notation, or do I have to convert
the
dbz array to 1D, select the points out in some rather nasty fashion,
and then convert back to 2D?
Any help would be appreciated, as I am trying to get a nice figure
done for the meso/radar conference next week..
Cheers!
Lou Wicker
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