CDO

Hi all,

The topic has been discussed in several threads through the years but I did not find a solution for my problem, unfortunately. My input file is a CMIP5 model file (BNU-ESM) which is on a curvilinear grid. ncdump -h looks like the following:

dimensions:
x = 360 ;
y = 200 ;
nv4 = 4 ;
time = UNLIMITED ; // (1 currently)
bnds = 2 ;
variables:
float lon(y, x) ;
lon:standard_name = "longitude" ;
lon:long_name = "longitude coordinate" ;
lon:units = "degrees_east" ;
lon:_CoordinateAxisType = "Lon" ;
lon:bounds = "lon_bnds" ;
float lon_bnds(y, x, nv4) ;
float lat(y, x) ;
lat:standard_name = "latitude" ;
lat:long_name = "latitude coordinate" ;
lat:units = "degrees_north" ;
lat:_CoordinateAxisType = "Lat" ;
lat:bounds = "lat_bnds" ;
float lat_bnds(y, x, nv4) ;
double time(time) ;
time:standard_name = "time" ;
time:long_name = "time" ;
time:bounds = "time_bnds" ;
time:units = "days since 1850-1-1 00:00:00" ;
time:calendar = "365_day" ;
time:axis = "T" ;
double time_bnds(time, bnds) ;
float tos(time, y, x) ;
tos:standard_name = "sea_surface_temperature" ;
tos:long_name = "Sea Surface Temperature" ;
tos:units = "K" ;
tos:coordinates = "lat lon" ;
tos:_FillValue = 1.e+20f ;
tos:missing_value = 1.e+20f ;
tos:comment = "\"this may differ from \"\"surface temperature\"\" in regions of sea ice.\"" ;
tos:cell_methods = "time: mean" ;

The following CDO command seems to convert the input file from curvilinear to a 1x1 degree regular lonlat grid without any error messages.

cdo remapnn,global_1 ltm_tos.nc ltm_tos_ll.nc

ncdump -h of the output file looks as following:

dimensions:
lon = 360 ;
lat = 180 ;
time = UNLIMITED ; // (1 currently)
bnds = 2 ;
variables:
double lon(lon) ;
lon:standard_name = "longitude" ;
lon:long_name = "longitude" ;
lon:units = "degrees_east" ;
lon:axis = "X" ;
double lat(lat) ;
lat:standard_name = "latitude" ;
lat:long_name = "latitude" ;
lat:units = "degrees_north" ;
lat:axis = "Y" ;
double time(time) ;
time:standard_name = "time" ;
time:long_name = "time" ;
time:bounds = "time_bnds" ;
time:units = "days since 1850-1-1 00:00:00" ;
time:calendar = "365_day" ;
time:axis = "T" ;
double time_bnds(time, bnds) ;
float tos(time, lat, lon) ;
tos:standard_name = "sea_surface_temperature" ;
tos:long_name = "Sea Surface Temperature" ;
tos:units = "K" ;
tos:_FillValue = 1.e+20f ;
tos:missing_value = 1.e+20f ;

Longitude values go as expected from -179.5 to 179.5. However, when visualising the the output file using ncview there seems to be a distortion in the longitude direction (see attached image). Africa should be at the centre of the image. Also, the lon and lat variables are not shown in the ncview interface which they usually are. So something has gone wrong somewhere but I am unable to figure it out. Any pointers would be much appreciated.

I am using CDO v1.7.

Thanks,
Sebastian