[ncl-talk] SSP interpolation

[Dennis Shea]

I don't think there is a function but for rectilinear grids (ie: lat[*],
lon[*] )

*cell_area*= (pi/180)*R^2* ((sind(lat(i)*rad) - sind(lat(j)*rad))*dlon);  *dlon
in radians*

R:  radius of earth: rearth = 6371.220      ; default; kilometers; ECMWF
uses this value

see: *get_d2r*
<http://www.ncl.ucar.edu/Document/Functions/Contributed/get_d2r.shtml>,
*get_pi*
<http://www.ncl.ucar.edu/Document/Functions/Contributed/get_pi.shtml>

EG:




*rad = 0.0174532925199433 (double)rad = 0.01745329  (float)*

For 2D lat/lon*, *it would be a bit more tedious





On Wed, Apr 21, 2021 at 8:27 AM Buzan, Jonathan via ncl-talk <
ncl-talk at mailman.ucar.edu> wrote:

> Hi NCL-Talk,
>
> I am working with SSP files. They are incomplete 1km x 1km lat-lon grids
> (aka the omit high latitudes), with missing/fill values over oceans. The
> population data is absolutes, not density per area. All of this makes it
> hard to interpolate to a low resolution grid approximate to CMIP data (aka
> 100 km x 100 km).
>
> I was thinking that I would divide each grid cell by the area to get a
> density value, then interpolate that to 1°x1° grid. But, I am having
> trouble finding a NCL function that will calculate the area of a grid cell.
>
> Is there one?
>
> Cheers,
> -Jonathan
>
>
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