Merge branch 'singhbalwinder/eamxx/precribe-o3-mam4xx' (PR #7539)

EAMxx: Adds prescribed Ozone option for MAM4xx

The user can now select whether to use prescribed or prognostic O3.
Selecting prescribed O3 disables LINOZ calculations of stratospheric O3.

Namelist switch: use_mam4_precribed_ozone
Current default: false

The switch above also replaces the mam4_run_linoz namelist.

Removes redundant addition of gases as tracers in the optics interface.

[BFB]

* singhbalwinder/eamxx/precribe-o3-mam4xx:
  Moves option to base mam4 xml tag
  Fix a space in the comments
  Adds static compile time error checking
  EAMxx: Adds option for prescribed Ozone in MAM4xx

Author: singhbalwinder

components/eamxx/cime_config/namelist_defaults_eamxx.xml

@@ -274,9 +274,9 @@ be lost if SCREAM_HACK_XML is not enabled.
     <!-- Basic options for each mam4 atm process -->
     <mam4_atm_proc_base inherit="atm_proc_base">
       <create_fields_interval_checks type="logical" doc="Create field interval checks for all fields that are computed and requested in mam4xx." >false</create_fields_interval_checks>
+      <use_mam4_precribed_ozone type="logical" doc="Switch to enable prescribed ozone in MAM4xx">false</use_mam4_precribed_ozone>
     </mam4_atm_proc_base>
 
-
     <!-- MAM4xx-ACI -->
     <mam4_aci inherit="mam4_atm_proc_base">
       <wsubmin type="real" doc="Minimum diagnostic sub-grid vertical velocity">0.001</wsubmin>
@@ -312,7 +312,6 @@ be lost if SCREAM_HACK_XML is not enabled.
       <mam4_do_coag   type="logical" doc="Switch to enable aerosol microphysics coagulation process">true</mam4_do_coag>
       <mam4_do_rename type="logical" doc="Switch to enable aerosol microphysics rename process">true</mam4_do_rename>
       <!-- LINOZ parameters -->
-      <mam4_run_linoz    type="logical"    doc="turn on/off linoz computation">true</mam4_run_linoz>
       <mam4_o3_tau    type="real"    doc="Linoz tau parameter">172800.0</mam4_o3_tau>
       <mam4_o3_sfc    type="real"    doc="Linoz surface parameter">3.0E-008</mam4_o3_sfc>
       <mam4_o3_lbl    type="integer" doc="Linoz lbl parameter">4</mam4_o3_lbl>

components/eamxx/src/physics/mam/eamxx_mam_generic_process_interface.cpp

@@ -10,6 +10,7 @@ namespace scream {
 MAMGenericInterface::MAMGenericInterface(const ekat::Comm &comm,
                                          const ekat::ParameterList &params)
     : AtmosphereProcess(comm, params) {
+      use_prescribed_ozone_   = m_params.get<bool>("use_mam4_precribed_ozone", false);
   /* Anything that can be initialized without grid information can be
    * initialized here. Like universal constants, mam wetscav options.
    */
@@ -50,8 +51,7 @@ void MAMGenericInterface::set_aerosol_and_gas_ranges() {
   }
 
   for(int g = 0; g < mam_coupling::num_aero_gases(); ++g) {
-    const std::string gas_mmr_field_name = mam_coupling::gas_mmr_field_name(g);
-    limits_aerosol_gas_tracers_[gas_mmr_field_name] =
+    limits_aerosol_gas_tracers_[std::string(mam_coupling::gas_mmr_name[g])] =
         mam_coupling::physical_min_max(mmr_label);
   }  // end for loop num gases
 }
@@ -99,6 +99,7 @@ void MAMGenericInterface::add_fields_cloudborne_aerosol() {
   auto n_unit           = 1 / kg;   // units of number mixing ratios of tracers
   const auto &grid_name = grid_->name();
 
+  //Layout for 3D scalar fields at midpoints(col, level))
   FieldLayout scalar3d_mid = grid_->get_3d_scalar_layout(true);
 
   // ---------------------------------------------------------------------
@@ -167,11 +168,30 @@ void MAMGenericInterface::add_tracers_interstitial_aerosol() {
 // ================================================================
 
 void MAMGenericInterface::add_tracers_gases() {
+  //Note that the gas list in MAM4 is: 
+  //{"O3",  "H2O2", "H2SO4", "SO2", "DMS",  "SOAG"}
   using namespace ekat::units;
-  auto q_unit = kg / kg;  // units of mass mixing ratios of tracers
-  for(int g = 0; g < mam_coupling::num_aero_gases(); ++g) {
-    const std::string gas_mmr_field_name = mam_coupling::gas_mmr_field_name(g);
-    add_tracer<Updated>(gas_mmr_field_name, grid_, q_unit);
+  constexpr auto q_unit = kg / kg;  // units of mass mixing ratios of tracers
+  const auto &grid_name = grid_->name();
+
+  //Layout for 3D scalar fields at midpoints(col, level))
+  const FieldLayout scalar3d_mid = grid_->get_3d_scalar_layout(true);
+
+  //O3 can be prescribed or prognostic depending upon the user input
+  //Index of Ozone in the gas list (currently order of species is fixed)
+  constexpr int o3_id = 0;
+  static_assert(mam_coupling::gas_mmr_name[o3_id] == "O3", "The first gas must be O3");
+  if (use_prescribed_ozone_) {
+    // If using prescribed O3, we add it as a field
+    add_field<Updated>(std::string(mam_coupling::gas_mmr_name[o3_id]), scalar3d_mid, q_unit, grid_name);
+  } else {
+    // If not using prescribed O3 (i.e., prognostic O3), we add it as a tracer
+    add_tracer<Updated>(std::string(mam_coupling::gas_mmr_name[o3_id]), grid_, q_unit);
+  }
+
+  // add other gases as tracers (note that the index of gases starts from 1)
+  for(int g = 1; g < mam_coupling::num_aero_gases(); ++g) {
+    add_tracer<Updated>(std::string(mam_coupling::gas_mmr_name[g]), grid_, q_unit);
   }  // end for loop num gases
 }
 // ================================================================
@@ -252,8 +272,7 @@ void MAMGenericInterface::set_buffer_scratch_to_zero(
 void MAMGenericInterface::populate_gases_wet_aero(
     mam_coupling::AerosolState &wet_aero) {
   for(int g = 0; g < mam_coupling::num_aero_gases(); ++g) {
-    const std::string gas_mmr_field_name = mam_coupling::gas_mmr_field_name(g);
-    wet_aero.gas_mmr[g] = get_field_out(gas_mmr_field_name).get_view<Real **>();
+    wet_aero.gas_mmr[g] = get_field_out(std::string(mam_coupling::gas_mmr_name[g])).get_view<Real **>();
   }
 }
 

components/eamxx/src/physics/mam/eamxx_mam_generic_process_interface.hpp

@@ -75,6 +75,9 @@ class MAMGenericInterface : public scream::AtmosphereProcess {
       const std::map<std::string, std::pair<Real, Real>> &max_min_process);
   void set_buffer_scratch_to_zero(mam_coupling::Buffer &buffer);
 
+  //namelist variables (declared protected so that derived classes can access them)
+  bool use_prescribed_ozone_{false};  // use prescribed ozone from MAM4
+
  private:
   // The type of subcomponent
   // --------------------------------------------------------------------------

components/eamxx/src/physics/mam/eamxx_mam_microphysics_process_interface.cpp

@@ -35,7 +35,8 @@ MAMMicrophysics::MAMMicrophysics(const ekat::Comm &comm,
   config_.amicphys.newnuc_h2so4_conc_optaa = 2;
 
   // LINOZ namelist parameters
-  config_.linoz.compute = m_params.get<bool>("mam4_run_linoz", true);
+  // Compute LINOZ only for prognostic Ozone (i.e. !use_prescribed_ozone_)
+  config_.linoz.compute = !use_prescribed_ozone_;
 
   if (config_.linoz.compute) {
     config_.linoz.o3_lbl = m_params.get<int>("mam4_o3_lbl");

components/eamxx/src/physics/mam/eamxx_mam_optics_process_interface.cpp

@@ -85,13 +85,7 @@ void MAMOptics::set_grids(
   add_tracers_gases();
   // add fields e.g., num_c1, soa_c1
   add_fields_cloudborne_aerosol();
-
-  // aerosol-related gases: mass mixing ratios
-  for(int g = 0; g < mam_coupling::num_aero_gases(); ++g) {
-    const char *gas_mmr_field_name = mam_coupling::gas_mmr_field_name(g);
-    add_tracer<Updated>(gas_mmr_field_name, grid_, kg / kg);
-  }
-}
+} //set_grids
 
 size_t MAMOptics::requested_buffer_size_in_bytes() const {
   return mam_coupling::buffer_size(ncol_, nlev_, num_2d_scratch_,

components/eamxx/src/physics/mam/mam_coupling.hpp

@@ -48,10 +48,6 @@ constexpr int gas_pcnst() {
 
 constexpr const char *num_modes_tag_name() { return "nmodes"; }
 
-// number of aerosol/gas species tendencies
-KOKKOS_INLINE_FUNCTION
-constexpr int nqtendbb() { return 4; }
-
 // returns the number of distinct aerosol modes
 KOKKOS_INLINE_FUNCTION
 constexpr int num_aero_modes() { return mam4::AeroConfig::num_modes(); }
@@ -96,14 +92,8 @@ const char *aero_species_name(const int species_id) {
   return species_names[species_id];
 }
 
-// Given a MAM aerosol-related gas ID, returns a string denoting the symbolic
-// name of the gas species.
-KOKKOS_INLINE_FUNCTION
-const char *gas_species_name(const int gas_id) {
-  static const char *species_names[num_aero_gases()] = {"O3",  "H2O2", "H2SO4",
-                                                        "SO2", "DMS",  "SOAG"};
-  return species_names[gas_id];
-}
+// Given a MAM aerosol-related gas ID, returns a string_view denoting the symbolic
+constexpr std::array<std::string_view, num_aero_gases()> gas_mmr_name= {"O3",  "H2O2", "H2SO4", "SO2", "DMS",  "SOAG"};
 
 // here we provide storage for names of fields generated by the functions below
 namespace {
@@ -165,12 +155,6 @@ char *cld_aero_mmr_names(int mode, int species) {
   return cld_aero_mmr_names_[mode][species];
 }
 
-KOKKOS_INLINE_FUNCTION
-char *gas_mmr_names(int gas_id) {
-  static char gas_mmr_names_[num_aero_gases()][max_field_name_len()] = {};
-  return gas_mmr_names_[gas_id];
-}
-
 }  // end anonymous namespace
 
 // Given a MAM aerosol mode index, returns the name of the related interstitial
@@ -227,13 +211,6 @@ const char *cld_aero_mmr_field_name(const int mode, const int species) {
   return const_cast<const char *>(cld_aero_mmr_names(mode, species));
 };
 
-// Given a MAM aerosol-related gas identifier, returns the name of its mass
-// mixing ratio field in EAMxx
-KOKKOS_INLINE_FUNCTION
-const char *gas_mmr_field_name(const int gas) {
-  return const_cast<const char *>(gas_species_name(gas));
-}
-
 // This type stores multi-column views related specifically to the wet
 // atmospheric state used by EAMxx.
 struct WetAtmosphere {