used json as file name extension

atm/rrtmg_lw/getpapi.py

@@ -78,5 +78,5 @@ with open(sys.argv[1]) as f:
         else:
             print("Warning: kernel execution for papi %s is failed." % event)
 
-    with open("kernel_papi.log", "w") as kp:
+    with open("kernel_papi.json", "w") as kp:
         json.dump(data, kp)