ENH: improved error message in hydrometeor calculation

Author: wolfidan

src/pyrad_proc/pyrad/proc/process_echoclass.py

@@ -1612,13 +1612,20 @@ def process_hydroclass(procstatus, dscfg, radar_list=None):
 
         if (
             (refl_field not in radar.fields)
-            or (zdr_field not in radar.fields)
-            or (rhv_field not in radar.fields)
-            or (kdp_field not in radar.fields)
         ):
-            warn("Unable to create hydrometeor classification field. " + "Missing data")
+            warn("Unable to create hydrometeor classification field. " + "Missing dBZ field")
             return None, None
-
+        if (
+            (rhv_field not in radar.fields)
+        ):
+            warn("Unable to create hydrometeor classification field. " + "Missing RhoHV field")
+            return None, None
+        if (
+            (kdp_field not in radar.fields)
+        ):
+            warn("Unable to create hydrometeor classification field. " + "Missing KDP field")
+            return None, None
+       
         # user defined parameters
         centroids_file = dscfg.get("centroids_file", None)
         compute_entropy = dscfg.get("compute_entropy", False)