# Re: Interpolate WRF data on Mercator projection to Cartesian grid

From: Dennis Shea <shea_at_nyahnyahspammersnyahnyah>
Date: Mon, 30 Jan 2006 21:50:21 -0700 (MST)

> I need to interpolate WRF data on native Mercator projection to the x,
> y, z Cartesian coordinates. Please let me know whether or not NCL can do this
> and how. Thank you.
>

The question is a bit open-ended.

(1) If you want "cartesian" relative to the plot frame, you
could use the function "datatondc"

However, I do not think this is what you want.

(2) I think the "gc_latlon" function could be used

The following uses the equator as the "origin"

You could then write the x and y coordinates to a file.

I will request that the gc_latlon function be
made to operate on arrays. That will speed things up.

begin

lat1d = ndtooned( f->XLAT(0,:,:) )
lon1d = ndtooned( f->XLONG(0,:,:))
npts = dimsizes( lat1d )

lato = 0.0 ; origin
lono = 0.0

x = new ( npts, "float")
y = new ( npts, "float")

do n=0,npts-1
x(n) = gc_latlon(lato,lono, lato ,lon1d(n), 2,3) ; x-axis
y(n) = gc_latlon(lato,lono, lat1d(n),lono , 2,3) ; y-axis
if (lon1d(n).lt.0) then
x(n) = -1*x(n)
end if
if (lat1d(n).lt.0) then
y(n) = -1*y(n)
end if
print(lat1d(n)+" "+lon1d(n)+" "+x(n)+" "+y(n))
end do
end

HTH
D
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Received on Mon Jan 30 2006 - 21:50:21 MST

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