diff --git a/cime_config/usermods_dirs/cmip6_noresm_DECK/SourceMods/src.cam/preprocessorDefinitions.h b/cime_config/usermods_dirs/cmip6_noresm_DECK/SourceMods/src.cam/preprocessorDefinitions.h
deleted file mode 100644
index 3cf59ed3..00000000
--- a/cime_config/usermods_dirs/cmip6_noresm_DECK/SourceMods/src.cam/preprocessorDefinitions.h
+++ /dev/null
@@ -1,2 +0,0 @@
-#undef AEROCOM
-#define AEROFFL
diff --git a/cime_config/usermods_dirs/cmip6_noresm_hifreq/SourceMods/src.cam/preprocessorDefinitions.h b/cime_config/usermods_dirs/cmip6_noresm_hifreq/SourceMods/src.cam/preprocessorDefinitions.h
deleted file mode 100644
index 3cf59ed3..00000000
--- a/cime_config/usermods_dirs/cmip6_noresm_hifreq/SourceMods/src.cam/preprocessorDefinitions.h
+++ /dev/null
@@ -1,2 +0,0 @@
-#undef AEROCOM
-#define AEROFFL
diff --git a/cime_config/usermods_dirs/cmip6_noresm_hifreq_xaer/SourceMods/src.cam/preprocessorDefinitions.h b/cime_config/usermods_dirs/cmip6_noresm_hifreq_xaer/SourceMods/src.cam/preprocessorDefinitions.h
deleted file mode 100644
index 3803258b..00000000
--- a/cime_config/usermods_dirs/cmip6_noresm_hifreq_xaer/SourceMods/src.cam/preprocessorDefinitions.h
+++ /dev/null
@@ -1,2 +0,0 @@
-#define AEROCOM
-#define AEROFFL
diff --git a/cime_config/usermods_dirs/cmip6_noresm_hifreq_xaer/shell_commands b/cime_config/usermods_dirs/cmip6_noresm_hifreq_xaer/shell_commands
new file mode 100644
index 00000000..0188a07e
--- /dev/null
+++ b/cime_config/usermods_dirs/cmip6_noresm_hifreq_xaer/shell_commands
@@ -0,0 +1,2 @@
+# Turn on AEROCOM diagnostic output
+./xmlchange AEROCOM=TRUE
diff --git a/cime_config/usermods_dirs/cmip6_noresm_keyCLIM/SourceMods/src.cam/preprocessorDefinitions.h b/cime_config/usermods_dirs/cmip6_noresm_keyCLIM/SourceMods/src.cam/preprocessorDefinitions.h
deleted file mode 100644
index 3cf59ed3..00000000
--- a/cime_config/usermods_dirs/cmip6_noresm_keyCLIM/SourceMods/src.cam/preprocessorDefinitions.h
+++ /dev/null
@@ -1,2 +0,0 @@
-#undef AEROCOM
-#define AEROFFL
diff --git a/cime_config/usermods_dirs/cmip6_noresm_keyCLIM_ism/SourceMods/src.cam/preprocessorDefinitions.h b/cime_config/usermods_dirs/cmip6_noresm_keyCLIM_ism/SourceMods/src.cam/preprocessorDefinitions.h
deleted file mode 100644
index 3cf59ed3..00000000
--- a/cime_config/usermods_dirs/cmip6_noresm_keyCLIM_ism/SourceMods/src.cam/preprocessorDefinitions.h
+++ /dev/null
@@ -1,2 +0,0 @@
-#undef AEROCOM
-#define AEROFFL
diff --git a/cime_config/usermods_dirs/cmip6_noresm_xaer/SourceMods/src.cam/preprocessorDefinitions.h b/cime_config/usermods_dirs/cmip6_noresm_xaer/SourceMods/src.cam/preprocessorDefinitions.h
deleted file mode 100644
index 3803258b..00000000
--- a/cime_config/usermods_dirs/cmip6_noresm_xaer/SourceMods/src.cam/preprocessorDefinitions.h
+++ /dev/null
@@ -1,2 +0,0 @@
-#define AEROCOM
-#define AEROFFL
diff --git a/cime_config/usermods_dirs/cmip6_noresm_xaer/shell_commands b/cime_config/usermods_dirs/cmip6_noresm_xaer/shell_commands
new file mode 100644
index 00000000..0188a07e
--- /dev/null
+++ b/cime_config/usermods_dirs/cmip6_noresm_xaer/shell_commands
@@ -0,0 +1,2 @@
+# Turn on AEROCOM diagnostic output
+./xmlchange AEROCOM=TRUE