negate navigation y per 3ebfc9ab

PUG has negative y north of equator

himawari/ahi2cmi.py

@@ -379,8 +379,8 @@ class HimawariAHIasCMIP(object):
                 'units': 'rad',
                 'long_name': "AHI fixed grid projection %s-coordinate" % name,
                 'standard_name': "projection_%s_coordinate" % name,
-                'scale_factor': m,
-                'add_offset': b
+                'scale_factor': -m if name=='y' else m,  # PUG has negative y north of equator
+                'add_offset': -b if name=='y' else b  # ref GIT 3ebfc9ab1f
             }
             # y/x
             yield self.p(name), v, self.d(name), a