CDO

Hi Cat,

see https://code.mpimet.mpg.de/projects/cdo/embedded/cdo.pdf#subsection.1.4.2 pre-defined grids (global_).

0.016667 degree =  1'
0.16667 degree  = 10'

cdo -remapcon,global_0.16667 pr_Amon_CNRM-CM6-1_historical_r3i1p1f2_gr_185001-201412.nc out.nc

-Karin

Hi Karen,

Thanks very much for that.
Cat

Sorry...'Karin'

Hi, I have a follow up question regarding this topic if that's ok?

Is there a way to 'check' the spatial resolution of an existing nc file? Sort of reverse-engineering the cdo above that specifies the global grid to be 10' or 1'?

Many thanks.

hi Cat!

you can output a text representation of your grid with

cdo griddes <ifile>

cdo griddes -topo   
cdo(1) topo: Process started
#
# gridID 1
#
gridtype  = lonlat
gridsize  = 259200
xsize     = 720
ysize     = 360
xname     = lon
xlongname = "longitude" 
xunits    = "degrees_east" 
yname     = lat
ylongname = "latitude" 
yunits    = "degrees_north" 
xfirst    = -179.75
xinc      = 0.5
yfirst    = -89.75
yinc      = 0.5
cdo(1) topo: 
cdo    griddes: Processed 1 variable [0.00s 42MB].

There is also a verification operator for horizontal grids

cdo verifygrid <ifile>

cdo verifygrid -topo
cdo(1) topo: Process started
cdo    verifygrid: Grid consists of 259200 (720x360) cells (type: lonlat), of which
cdo    verifygrid:    259200 cells have 4 vertices
cdo    verifygrid:      1440 cells have duplicate vertices
cdo    verifygrid:        lon : -179.75 to 179.75 degrees
cdo    verifygrid:        lat : -89.75 to 89.75 degrees
cdo(1) topo: 
cdo    verifygrid: Processed 1 variable [0.38s 86MB].

Hope that helps,
ralf

And, yes - of course you can pick an old topic ;-)
have good weekend

Hi Ralf,

Thanks for your comprehensive answer.

Can you tell me if elevation is taken into account using this cdo for interpolation?
Many thanks.

happy new year, cat ;-)

your request seems a but too general. this depends on the specific input file and the interpolation methods you want to use on which variable.

cheers
ralf

Happy new year to you too:)
Apologies. I used 'remapcon' to regrid a global temperature grid to a more coarse resolution. I suppose what I am asking is if elevation factors in to the 'remapcon' command when being ran for climate variables. I looked at the documentation and saw no mention of elevation being accounted for. It is just a straight interpolation as opposed to one that is dependent on elevation data?

In general the elevation of a source or target grid cell has no influence on any horizontal remapping, because in most cases it is simply not given. Depending on the method the location(s), cell area(s) or distance(s) are used to compute the interpolation weights since this information is easily available in the input. 'cell elevation' can be very specific to the model or the input/output resolution. It's not clear what is the right algorithm for desired application, so we have to get to the details first, I guess:

• How exactly to you want to include cell elevation into a horizontal interpolation?
  • Maybt it can already be done with the right operator combination
  • Maybe it's worth having a new interpolation method for this in CDO (I hereby suggest to call it remapmeow in that case)
• Do you have input ready to testing?
• Is there an article published about this, which can be used for reference?

have a nice day - or good night, idk.

cheers
ralf