Added function streamGrbChangeModeUvRelativeToGrid().

src/stream_cgribex.c

@@ -1831,6 +1831,18 @@ void cgribexDefGrid(int *isec1, int *isec2, double *fsec2, int *isec4, int gridI
 	break;
       }
     }
+
+
+  if ( cdiGribChangeModeUvRelativeToGrid.active )
+    {
+      // this will overrule/change the UvRelativeToGrid flag;
+      // typically when the wind is rotated with respect to north pole
+      bool uvRelativeToGrid = bit_get(ISEC2_ResFlag, 3);
+      if      ( uvRelativeToGrid && !cdiGribChangeModeUvRelativeToGrid.mode )
+        ISEC2_ResFlag -= 8;
+      else if ( !uvRelativeToGrid && cdiGribChangeModeUvRelativeToGrid.mode )
+        ISEC2_ResFlag += 8;
+    }
 }
 
 static

src/stream_grb.c

@@ -15,7 +15,7 @@
 // change if cdiGribChangeParameterID.active
 struct cdiGribParamChange cdiGribChangeParameterID;
 
-// Used only in CDO
+// Used only for CDO module Selmulti
 void streamGrbChangeParameterIdentification(int code, int ltype, int lev)
 {
   // NOTE this is a "PROXY" function for gribapiChangeParameterIdentification();
@@ -29,6 +29,15 @@ void streamGrbChangeParameterIdentification(int code, int ltype, int lev)
   cdiGribChangeParameterID.lev = lev;
 }
 
+struct cdiGribModeChange cdiGribChangeModeUvRelativeToGrid;
+
+// Used only for CDO module WindTrans
+void streamGrbChangeModeUvRelativeToGrid(int mode)
+{
+  cdiGribChangeModeUvRelativeToGrid.active = true;
+  cdiGribChangeModeUvRelativeToGrid.mode = (mode > 0);
+}
+
 
 int grib1ltypeToZaxisType(int grib_ltype)
 {

src/stream_grb.h

@@ -30,9 +30,17 @@ struct cdiGribParamChange
   bool active;
 };
 
+struct cdiGribModeChange
+{
+  bool mode;
+  bool active;
+};
+
 extern struct cdiGribParamChange cdiGribChangeParameterID;
+extern struct cdiGribModeChange cdiGribChangeModeUvRelativeToGrid;
 
 void streamGrbChangeParameterIdentification(int code, int ltype, int lev);
+void streamGrbChangeModeUvRelativeToGrid(int mode);
 
 #endif  /* _STREAM_GRB_H */
 /*

src/stream_gribapi.c

@@ -2677,6 +2677,13 @@ size_t gribapiEncode(int varID, int levelID, int vlistID, int gridID, int zaxisI
       GRIB_CHECK(my_grib_set_double(gh, "missingValue", vlistInqVarMissval(vlistID, varID)), 0);
     }
 
+  if ( cdiGribChangeModeUvRelativeToGrid.active )
+    {
+      // this will overrule/change the UvRelativeToGrid flag;
+      // typically when the wind is rotated with respect to north pole
+      GRIB_CHECK(my_grib_set_long(gh, "uvRelativeToGrid", (long) cdiGribChangeModeUvRelativeToGrid.mode), 0);
+    }
+
   GRIB_CHECK(grib_set_double_array(gh, "values", data, (size_t)datasize), 0);
 
   /* get the size of coded message  */