added a clarifying comment on covariance localization for parameters

models.py

@@ -47,6 +47,7 @@ class CBL:
             # If desired, append parameters to state vector;
             # initialize with the value in the middle of the admitted range
             # Coordinates of parameters are set to NaN
+            # The reason is that parameters are assumed to be global.
             if self.do_parameter_estimation:
                 if self.nens > 1:
                     for k in range(-self.parameter_number,0):