file = NetcdfFileWriteable.openExisting(url, false);
file.setRedefineMode(true);
//Group rootGroup = file.getRootGroup();
//Group headerDataGroup = new Group(file, rootGroup, "header_data");
//file.addGroup(rootGroup, headerDataGroup);
file.addVariable(null, newVarName, DataType.FLOAT, "z y x");
} finally {
if (file != null) {
file.setRedefineMode(false);
file.flush();
file.close();