How to convert sigma-levels to geometric height?

[jdorrington]

Hi,

I am analysing some CESM2 atmospheric temperature data, stored on sigma levels. In order to ultimately compute lapse rate, I am trying to interpolate the data to geometric height.
I have tried the following procedure:

#relates ilev to lev for purposes of vertical interpolation. ncatted comes from NCO

ncatted -a bounds,lev,c,c,"ilev" test_3d_T.nc

#attempt to use cdo to go from model levels to height

cdo -ml2hl,1000,2000,3000 -selname,T test_3d_T.nc test_height_data.nc

This fails with the error

cdo ml2hl (Abort): surface_air_pressure not found!

If I don't try to select a variable first, I get a different error:

cdo -ml2hl,1000,2000,3000 test_3d_T.nc test_height_data.nc

Warning (cdfCheckVars): Unsupported data type (char/string), skipped variable date_written!
Warning (cdfCheckVars): Unsupported data type (char/string), skipped variable time_written!
cdo ml2hl: This operator requires all variables on the same horizontal grid.
cdo ml2hl: Horizontal grids found:
cdo ml2hl: grid=1 type=lonlat points=192
cdo ml2hl: grid=2 type=generic points=1
cdo ml2hl: grid=3 type=lonlat points=55296

cdo ml2hl (Abort): The input stream contains variables on different horizontal grids!

Any help would be much appreciated, I'm tearing my hair out with this one!!