WEIGHTS produces bad values

Hello again.)

To initialize the model (global ORCA2), I use the global ocean analysis and forecast 1/12 degree data from CMEMS. There are no runtime errors when creating weights using the WEIGHTS tool from the dataset coordinate grid to the ORCA_R2_zps_domcfg coordinate grid (default from ORCA2_ICE_PISCES). However, when viewing the resulting interpolation weights, it’s found that in the variables wgt03 and wgt04 there is one value approximately 2160 and -2160, respectively. Although the interpolation weights should be within [0,1].
This effect is observed with map_method = [‘bilinear’,‘bicubic’] and with ew_wrap = [-1,0,1,2]. Coordinates of the point → 179.99992124 E, 0.0 N.
When calculating interpolation weights for forcing (global gfs data), no such effect is observed.
Illustrating weights maps and namelist_bilin are attached below.

All weights variables (lat=y, lon=x in ORCA grid)

 - grid_inputs holds parameters for the scripgrid routine which reformats information 
   about the input grids
 - scripgrid always needs a coordinates.nc file in the
   current directory and creates the remapped grid file correspondingly
 - it uses the following namelist block to determine its actions
     method:  only 'regular' is yet implemented, this assumes a cartesian grid
     input_lon: name of longitude variable in the input_file
     input_lat: name of latitude variable in the input_file
     nemo_lon: name of longitude variable in the coordinates.nc
     nemo_lat: name of latitude variable in the coordinates.nc
    input_file = 'gl12_mean_20230130_R20230201.nc'
    nemo_file = 'ORCA_R2_zps_domcfg.nc'
    datagrid_file = 'remap_glorys_grid.nc'
    nemogrid_file = 'remap_ORCA2_grid.nc'
    method = 'regular'
    input_lon = 'longitude'
    input_lat = 'latitude'
    nemo_lon = 'glamt'
    nemo_lat = 'gphit'
    nemo_mask = 'none'
    nemo_mask_value = 10
    input_mask = 'none'
    input_mask_value = 10
 - remap_inputs holds parameters for the scrip routine which calculates the weights
   needed to convert between two grids
 - two remap grid files are required as output by scripgrid
 - num_maps is either 1 or 2 depending on whether the reverse transformation is required
 - one or two interp_file names are then supplied; these hold the weights to convert 
   one grid to another
 - the map_name variable is just descriptive
 - map_method can be 'bilinear' 'bicubic' or 'conservative' (the latter untested)
 - normalize_opt should usually be 'frac' or else the user needs to do this scaling
   manually (this seems to the case for fractional ice cover)
 - restrict_type should be 'latitude' or 'latlon' in which case num_srch_bins only are 
   used in one or two directions
 - use_grid_area fields override the scrip calculation of area in case the model gets
   slightly different answers, but the area needs to be supplied in the input files
 - output_opt may be supplied and set to either 'scrip' or 'ncar-csm'
    num_maps = 1
    grid1_file = 'remap_glorys_grid.nc'
    grid2_file = 'remap_ORCA2_grid.nc'
    interp_file1 = 'glorys_ORCA2_bilin.nc'
    interp_file2 = 'ORCA2_glorys_bilin.nc'
    map1_name = 'glorys to ORCA2 bilin Mapping'
    map2_name = 'ORCA2 to glorys bilin Mapping'
    map_method = 'bilinear'
    normalize_opt = 'frac'
    output_opt = 'scrip'
    restrict_type = 'latitude'
    num_srch_bins = 90 
    luse_grid1_area = .false.
    luse_grid2_area = .false.

    input_file = "t_10.15JUNE2009_fill.nc"
    interp_file = "core2_nordic1_bilin.nc"
    input_name = "T_10_MOD"
    input_start = 1,1,1,1
    input_stride = 1,1,1,1
    input_stop = 0,0,0,1
    input_vars = 'initial_time0_hours'

    output_file = "t_10.15JUNE2009_nordic1.nc"
    output_mode = "create"
    output_dims = 'x', 'y', 'time_counter'
    output_scaling = "T_10_MOD|1.0", "time_counter|86400.0"
    output_name = 'T_10_MOD'
    output_lon = 'x'
    output_lat = 'y'
    output_vars = 'time_counter'
    output_attributes = 'time_counter|units|seconds since 1995-00-00 00:00:00',

 -  shape_inputs are the input fields required by scripshape.f90
 -  first is the interpolation file created by scrip.f90 mapping data to model grid
 -  second is the name of the output weights file to create
 -  third is the east-west wrap to assume in the model (needed when calculating gradient 
          terms in the bicubic scheme); the number is just the number of columns on one side
          that are repeats of those on the opposite side (-1 for not cyclic)
    interp_file = 'glorys_ORCA2_bilin.nc'
    output_file = 'weights_glorys_ORCA2_bilin.nc'
    ew_wrap     = 0

What could be the cause of the error?

Dear m-n-o

I tried the same thing and I have the same error, were you able to fix it? Thanks for your answer

How are the longitudes for your forcing arranged? Are they from 0-360 or -180.0-179? Can you check that?

1 Like

I checked the lengths and yes it is 0-360, I used the same forcing file to create a “weight” file in a regional zone and yes it works fine. The problem is with the global configuration, if anyone can fix it please tell me.

Hello, Elsy.
I had changed my focus on preprocessing interpolation via SOSIE and it works fine.)

1 Like

I think I found the problem if anyone is interested in this, you first need to make sure the lengths are ordered from smallest to largest and with values from 0 to 360, then check if the grid points in your database are greater, less or equal to the grid to be modeled. In case you get zero in your “wgt01” or any “wgt0*” values this indicates that the database point is closer to the grid point, so when applying the weight equation (which it is a sum, manual v4.0.6 - Pg. 71) some may be zero or very small values. To verify that the “weigths*.nc” file is correct execute “scripinterp.exe” (before edit “namelist*”) to obtain a netCDF file from your database gridded with the grid to be modeled. There is no detailed description for editing the “namelist” section for “scripinterp” if you need help you can write to me :slightly_smiling_face: