add brtemp and cldmask under diag var_struct of src/core_atmosphere/Registry.xml (MPAS-Dev#43)

DESCRIPTION OF CHANGES:
For a madwrf algorithm in SACA repository, two variables `brtemp` and `cldmask` are added under `diag` var_struct of `Registry.xml`.

LIST OF MODIFIED FILES:
src/core_atmosphere/Registry.xml

TESTS CONDUCTED: Tested on Cheyenne.

Author: byoung-joo

src/core_atmosphere/Registry.xml

@@ -1839,6 +1839,15 @@
                 <var name="surface_pressure" type="real" dimensions="nCells Time" units="Pa"
                      description="Diagnosed surface pressure"/>
 
+                <!-- observation-related variables interfacing to Non-Variational SAtellite-based Cloud Analysis (SACA)  -->
+                <var name="cldmask" type="real" dimensions="nCells Time" units="unitless"
+                     description="cloud mask (1=cloudy ; 0=clear)"
+                     packages="jedi_da"/>
+
+                <var name="brtemp" type="real" dimensions="nCells Time" units="K"
+                     description="brightness temperature to calculate cloud top height; usually from geostationary IR window channel"
+                     packages="jedi_da"/>
+
         </var_struct>
 
         <var_struct name="tend" time_levs="1">