cdi_write_curv_rll.c 3.42 KB
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#include <stdio.h>
#include "cdi.h"

int main(void)
{
  const int nlon = 12; // Number of longitudes
  const int nlat =  6; // Number of latitudes
  const int nlev =  5; // Number of levels
  const int nts  =  3; // Number of time steps
  size_t nmiss = 0;
  double levs[] = {101300, 92500, 85000, 50000, 20000};
  double var1[nlon*nlat];
  double var2[nlon*nlat*nlev];


  // Create a curvilinear grid
  int gridID = gridCreate(GRID_CURVILINEAR, nlon*nlat);
  {
    double lons[] = {0, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330};
    double lats[] = {-75, -45, -15, 15, 45, 75};

    double lons2D[nlon*nlat], lats2D[nlon*nlat];
    for (int j = 0; j < nlat; ++j)
      for (int i = 0; i < nlon; ++i)
        {
          lons2D[j*nlon+i] = lons[i];
          lats2D[j*nlon+i] = lats[j];
        }

    gridDefXsize(gridID, nlon);
    gridDefYsize(gridID, nlat);
    gridDefXvals(gridID, lons2D);
    gridDefYvals(gridID, lats2D);
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    cdiDefKeyString(gridID, CDI_XAXIS, CDI_KEY_NAME, "lon");
    cdiDefKeyString(gridID, CDI_YAXIS, CDI_KEY_NAME, "lat");
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  }

  // Create a rotated lon/lat grid
  {
    int projID = gridCreate(GRID_PROJECTION, nlon*nlat);
    double rlons[] = {10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65};
    double rlats[] = {5, 10, 15, 20, 25, 30};

    gridDefXsize(projID, nlon);
    gridDefYsize(projID, nlat);
    gridDefXvals(projID, rlons);
    gridDefYvals(projID, rlats);
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    cdiDefKeyString(projID, CDI_XAXIS, CDI_KEY_NAME, "rlon");
    cdiDefKeyString(projID, CDI_YAXIS, CDI_KEY_NAME, "rlat");

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    gridDefParamRLL(projID, -162., 39.25, 0);

    gridDefProj(gridID, projID);
  }

  // Create a surface level Z-axis
  int zaxisID1 = zaxisCreate(ZAXIS_SURFACE, 1);

  // Create a pressure level Z-axis
  int zaxisID2 = zaxisCreate(ZAXIS_PRESSURE, nlev);
  zaxisDefLevels(zaxisID2, levs);
 
  // Create a variable list
  int vlistID = vlistCreate();

  // Define the variables
  int varID1 = vlistDefVar(vlistID, gridID, zaxisID1, TIME_VARYING);
  int varID2 = vlistDefVar(vlistID, gridID, zaxisID2, TIME_VARYING);

  // Define the variable names
  vlistDefVarName(vlistID, varID1, "varname1");
  vlistDefVarName(vlistID, varID2, "varname2");

  // Create a Time axis
  int taxisID = taxisCreate(TAXIS_ABSOLUTE);

  // Assign the Time axis to the variable list
  vlistDefTaxis(vlistID, taxisID);

  // Create a dataset in netCDF format
  int streamID = streamOpenWrite("example.grb", CDI_FILETYPE_GRB2);
  if ( streamID < 0 )
    {
      fprintf(stderr, "%s\n", cdiStringError(streamID));
      return 1;
    }

  // Assign the variable list to the dataset
  streamDefVlist(streamID, vlistID);

  // Loop over the number of time steps
  for ( int tsID = 0; tsID < nts; tsID++ )
    {
      // Set the verification date to 1985-01-01 + tsID
      taxisDefVdate(taxisID, 19850101+tsID);
      // Set the verification time to 12:00:00
      taxisDefVtime(taxisID, 120000);
      // Define the time step
      streamDefTimestep(streamID, tsID);

      // Init var1 and var2
      for ( size_t i = 0; i < nlon*nlat;      i++ ) var1[i] = 1.1;
      for ( size_t i = 0; i < nlon*nlat*nlev; i++ ) var2[i] = 2.2;

      // Write var1 and var2
      streamWriteVar(streamID, varID1, var1, nmiss);
      streamWriteVar(streamID, varID2, var2, nmiss);
    }

  // Close the output stream
  streamClose(streamID);

  // Destroy the objects
  vlistDestroy(vlistID);
  taxisDestroy(taxisID);
  zaxisDestroy(zaxisID1);
  zaxisDestroy(zaxisID2);
  gridDestroy(gridID);

  return 0;
}