implement band_id dimension when as_cmi is requested

himawari/ahi2cmi.py

@@ -525,12 +525,16 @@ class HimawariAHIasCMIP(object):
         else:  # return floating point values
             return line, column
 
-    def walk(self, extra_data_attrs={}):
+    def walk(self, extra_data_attrs={}, as_cmi=False):
         """
         iterate PVDA frames equivalent to a PUG nc_walk
         """
+        BAND_ID_DIM = 'band_id'
         # root
-        yield self.p(), None, self._pug_global_dims, self._pug_global_attrs
+        gdims = OrderedDict(self._pug_global_dims)
+        if as_cmi:
+            gdims[BAND_ID_DIM] = 1
+        yield self.p(), None, gdims, self._pug_global_attrs
 
         # nav structure
         yield self.p(self._projection_name), np.int32(0), {}, self.nav
@@ -538,6 +542,10 @@ class HimawariAHIasCMIP(object):
         # band_wavelength in µm
         yield self.p('band_wavelength'), np.float64(self.central_wavelength), {}, {}
 
+        # band number, primarily for CMI
+        if as_cmi:
+            yield self.p('band_id'), np.array([self.band], dtype=np.int8), OrderedDict({BAND_ID_DIM: gdims[BAND_ID_DIM]}), {}
+
         # y and x variables and friends
         for each in self.pvda_yx():
             yield each
@@ -550,8 +558,13 @@ class HimawariAHIasCMIP(object):
             yield each
 
         # we almost forgot! the data itself
-        v = self.data
-        d = self.data_dims
+        if not as_cmi:  # SCMI has no band_id dimension
+            v = self.data
+            d = self.data_dims
+        else:
+            v = self.data.reshape((1,) + tuple(self.data.shape))
+            d = OrderedDict({BAND_ID_DIM: gdims[BAND_ID_DIM]})
+            d.update(self.data_dims)
         a = dict(self.data_attrs)
         a.update(extra_data_attrs)
         yield self.p(self._data_name), v, d, a