Merge Pull Request #2673 from E3SM-Project/scream/mahf708/nudging/fix…

…-grid-error

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PR Title: forbid using weighted nudging from coarse data
PR Author: mahf708
PR LABELS: AT: AUTOMERGE, nudging

components/eamxx/src/physics/nudging/eamxx_nudging_process_interface.cpp

@@ -115,6 +115,11 @@ void Nudging::set_grids(const std::shared_ptr<const GridsManager> grids_manager)
                      << std::to_string(m_num_cols_global) << " does not match the number of columns in the "
                      << "mapfile " << std::to_string(num_cols_remap_b) << ".  Please check the "
                      << "model grid and/or the mapfile.");
+    EKAT_REQUIRE_MSG(m_use_weights == false,
+                     "Error! Nudging::set_grids - it seems that the user intends to use both nuding "
+                     << "from coarse data as well as weighted nudging simultaneously. This is not supported. " 
+                     << "If the user wants to use both at their own risk, the user should edit the source code "
+                     << "by deleting this error message.");
     // If we get here, we are good to go!
     m_refine_remap = true;
   } else {