diff --git a/cime_config/namelist_definition_drv_flds.xml b/cime_config/namelist_definition_drv_flds.xml
index cef475978..beceb238c 100644
--- a/cime_config/namelist_definition_drv_flds.xml
+++ b/cime_config/namelist_definition_drv_flds.xml
@@ -145,4 +145,20 @@
     </desc>
   </entry>
 
+  <!-- ========================================================================================  -->
+  <!-- Ozone control                                                                              -->
+  <!-- ========================================================================================  -->
+
+  <entry id="atm_ozone_frequency">
+    <type>char</type>
+    <category>ozone_coupling</category>
+    <group>ozone_coupling_nl</group>
+    <desc>
+      Frequency of surface ozone field passed from CAM to surface components.
+      Surface ozone is passed every coupling interval, but this namelist flag
+      indicates whether the timestep-level values are interpolated from a
+      coarser temporal resolution.
+    </desc>
+  </entry>
+
 </entry_id>
diff --git a/mediator/esmFldsExchange_cesm_mod.F90 b/mediator/esmFldsExchange_cesm_mod.F90
index cd3f4726f..92893793c 100644
--- a/mediator/esmFldsExchange_cesm_mod.F90
+++ b/mediator/esmFldsExchange_cesm_mod.F90
@@ -27,7 +27,7 @@ module esmFldsExchange_cesm_mod
 
   public :: esmFldsExchange_cesm
 
-  ! currently required mapping files 
+  ! currently required mapping files
   character(len=CX)   :: glc2ice_rmap     ='unset'
   character(len=CX)   :: glc2ocn_liq_rmap ='unset'
   character(len=CX)   :: glc2ocn_ice_rmap ='unset'
@@ -375,6 +375,19 @@ subroutine esmFldsExchange_cesm(gcomp, phase, rc)
        end if
     end if
     ! ---------------------------------------------------------------------
+    ! to lnd: o3 at the lowest model level from atm
+    ! ---------------------------------------------------------------------
+    if (phase == 'advertise') then
+       call addfld(fldListFr(compatm)%flds, 'Sa_o3')
+       call addfld(fldListTo(complnd)%flds, 'Sa_o3')
+    else
+       if ( fldchk(is_local%wrap%FBexp(complnd)         , 'Sa_o3', rc=rc) .and. &
+            fldchk(is_local%wrap%FBImp(compatm,compatm ), 'Sa_o3', rc=rc)) then
+          call addmap(fldListFr(compatm)%flds, 'Sa_o3', complnd, mapbilnr, 'one', atm2lnd_map)
+          call addmrg(fldListTo(complnd)%flds, 'Sa_o3', mrg_from=compatm, mrg_fld='Sa_o3', mrg_type='copy')
+       end if
+    end if
+    ! ---------------------------------------------------------------------
     ! to lnd: temperature at the lowest model level from atm
     ! ---------------------------------------------------------------------
     if (phase == 'advertise') then
@@ -1838,7 +1851,7 @@ subroutine esmFldsExchange_cesm(gcomp, phase, rc)
     ! ---------------------------------------------------------------------
     ! Note that this is a field output by the atm/ocn flux computation
     ! If the aoflux grid is ogrid - then nothing needs to be done to send to the ocean
-    ! All other mappings are set in med_phases_aoflux_mod.F90 
+    ! All other mappings are set in med_phases_aoflux_mod.F90
     if (phase == 'advertise') then
        call addfld(fldListMed_aoflux%flds , 'So_duu10n')
        call addfld(fldListTo(compocn)%flds, 'So_duu10n')
diff --git a/mediator/fd_cesm.yaml b/mediator/fd_cesm.yaml
index 1a4889bc0..85e2101c6 100644
--- a/mediator/fd_cesm.yaml
+++ b/mediator/fd_cesm.yaml
@@ -318,6 +318,10 @@
        canonical_units: 1e-6 mol/mol
        description: atmosphere export - prognostic CO2 at the lowest model level
      #
+     - standard_name: Sa_o3
+       canonical_units: mol/mol
+       description: atmosphere export - O3 in the lowest model layer (prognosed or prescribed)
+     #
      - standard_name: Sa_topo
        alias: inst_surface_height
        canonical_units: m