issue_comments

https://github.com/pydata/xarray/issues/2233#issuecomment-397602084 Would the new xarray index/coordinate internal refactoring now allow us to address this issue?

cc @kthyng

@rabernat , this unstructured grid model output follows the UGRID Conventions, which layer on top of the CF Conventions. The issue Xarray is having here is with the vertical coordinate however, so this issue could arise with any CF convention model where the vertical stretching function varies over the domain.

As requested, here is the ncdump of this URL: ``` jovyan@jupyter-rsignell-2dusgs:~$ ncdump -h http://www.smast.umassd.edu:8080/thredds/dodsC/FVCOM/NECOFS/Forecasts/NECOFS_GOM3_FORECAST.nc netcdf NECOFS_GOM3_FORECAST { dimensions: time = UNLIMITED ; // (145 currently) maxStrlen64 = 64 ; nele = 99137 ; node = 53087 ; siglay = 40 ; three = 3 ; variables: float lon(node) ; lon:long_name = "nodal longitude" ; lon:standard_name = "longitude" ; lon:units = "degrees_east" ; float lat(node) ; lat:long_name = "nodal latitude" ; lat:standard_name = "latitude" ; lat:units = "degrees_north" ; float xc(nele) ; xc:long_name = "zonal x-coordinate" ; xc:units = "meters" ; float yc(nele) ; yc:long_name = "zonal y-coordinate" ; yc:units = "meters" ; float lonc(nele) ; lonc:long_name = "zonal longitude" ; lonc:standard_name = "longitude" ; lonc:units = "degrees_east" ; float latc(nele) ; latc:long_name = "zonal latitude" ; latc:standard_name = "latitude" ; latc:units = "degrees_north" ; float siglay(siglay, node) ; siglay:long_name = "Sigma Layers" ; siglay:standard_name = "ocean_sigma_coordinate" ; siglay:positive = "up" ; siglay:valid_min = -1. ; siglay:valid_max = 0. ; siglay:formula_terms = "sigma: siglay eta: zeta depth: h" ; float h(node) ; h:long_name = "Bathymetry" ; h:standard_name = "sea_floor_depth_below_geoid" ; h:units = "m" ; h:coordinates = "lat lon" ; h:type = "data" ; h:mesh = "fvcom_mesh" ; h:location = "node" ; int nv(three, nele) ; nv:long_name = "nodes surrounding element" ; nv:cf_role = "face_node_connnectivity" ; nv:start_index = 1 ; float time(time) ; time:long_name = "time" ; time:units = "days since 1858-11-17 00:00:00" ; time:format = "modified julian day (MJD)" ; time:time_zone = "UTC" ; time:standard_name = "time" ; float zeta(time, node) ; zeta:long_name = "Water Surface Elevation" ; zeta:units = "meters" ; zeta:standard_name = "sea_surface_height_above_geoid" ; zeta:coordinates = "time lat lon" ; zeta:type = "data" ; zeta:missing_value = -999. ; zeta:field = "elev, scalar" ; zeta:coverage_content_type = "modelResult" ; zeta:mesh = "fvcom_mesh" ; zeta:location = "node" ; int nbe(three, nele) ; nbe:long_name = "elements surrounding each element" ; float u(time, siglay, nele) ; u:long_name = "Eastward Water Velocity" ; u:units = "meters s-1" ; u:type = "data" ; u:missing_value = -999. ; u:field = "ua, scalar" ; u:coverage_content_type = "modelResult" ; u:standard_name = "eastward_sea_water_velocity" ; u:coordinates = "time siglay latc lonc" ; u:mesh = "fvcom_mesh" ; u:location = "face" ; float v(time, siglay, nele) ; v:long_name = "Northward Water Velocity" ; v:units = "meters s-1" ; v:type = "data" ; v:missing_value = -999. ; v:field = "va, scalar" ; v:coverage_content_type = "modelResult" ; v:standard_name = "northward_sea_water_velocity" ; v:coordinates = "time siglay latc lonc" ; v:mesh = "fvcom_mesh" ; v:location = "face" ; float ww(time, siglay, nele) ; ww:long_name = "Upward Water Velocity" ; ww:units = "meters s-1" ; ww:type = "data" ; ww:coverage_content_type = "modelResult" ; ww:standard_name = "upward_sea_water_velocity" ; ww:coordinates = "time siglay latc lonc" ; ww:mesh = "fvcom_mesh" ; ww:location = "face" ; float ua(time, nele) ; ua:long_name = "Vertically Averaged x-velocity" ; ua:units = "meters s-1" ; ua:type = "data" ; ua:missing_value = -999. ; ua:field = "ua, scalar" ; ua:coverage_content_type = "modelResult" ; ua:standard_name = "barotropic_eastward_sea_water_velocity" ; ua:coordinates = "time latc lonc" ; ua:mesh = "fvcom_mesh" ; ua:location = "face" ; float va(time, nele) ; va:long_name = "Vertically Averaged y-velocity" ; va:units = "meters s-1" ; va:type = "data" ; va:missing_value = -999. ; va:field = "va, scalar" ; va:coverage_content_type = "modelResult" ; va:standard_name = "barotropic_northward_sea_water_velocity" ; va:coordinates = "time latc lonc" ; va:mesh = "fvcom_mesh" ; va:location = "face" ; float temp(time, siglay, node) ; temp:long_name = "temperature" ; temp:standard_name = "sea_water_potential_temperature" ; temp:units = "degrees_C" ; temp:coordinates = "time siglay lat lon" ; temp:type = "data" ; temp:coverage_content_type = "modelResult" ; temp:mesh = "fvcom_mesh" ; temp:location = "node" ; float salinity(time, siglay, node) ; salinity:long_name = "salinity" ; salinity:standard_name = "sea_water_salinity" ; salinity:units = "0.001" ; salinity:coordinates = "time siglay lat lon" ; salinity:type = "data" ; salinity:coverage_content_type = "modelResult" ; salinity:mesh = "fvcom_mesh" ; salinity:location = "node" ; int fvcom_mesh ; fvcom_mesh:cf_role = "mesh_topology" ; fvcom_mesh:topology_dimension = 2 ; fvcom_mesh:node_coordinates = "lon lat" ; fvcom_mesh:face_coordinates = "lonc latc" ; fvcom_mesh:face_node_connectivity = "nv" ;

// global attributes: :title = "NECOFS GOM3 (FVCOM) - Northeast US - Latest Forecast" ; :institution = "School for Marine Science and Technology" ; :source = "FVCOM_3.0" ; :Conventions = "CF-1.0, UGRID-1.0" ; :summary = "Latest forecast from the FVCOM Northeast Coastal Ocean Forecast System using an newer, higher-resolution GOM3 mesh (GOM2 was the preceding mesh)" ;

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