# [ncl-talk] SSP interpolation

Buzan, Jonathan jbuzan at purdue.edu
Wed Apr 21 09:49:00 MDT 2021

```Thanks Dennis, I’ll work this out.

Cheers,
-Jonathan

On Apr 21, 2021, at 5:21 PM, Dennis Shea <shea at ucar.edu<mailto:shea at ucar.edu>> wrote:

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

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:

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<mailto: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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