Makes use_hetfrz_classnuc a runtime option and other minor changes

components/eamxx/cime_config/namelist_defaults_scream.xml

@@ -192,7 +192,7 @@ be lost if SCREAM_HACK_XML is not enabled.
     <!-- P3 microphysics -->
     <p3 inherit="atm_proc_base">
       <do_prescribed_ccn>true</do_prescribed_ccn>
-      <use_hetfrz_classnuc>true</use_hetfrz_classnuc>
+      <use_hetfrz_classnuc type="logical" doc="Switch to turn on heterogeneous freezing due to prognostic aerosols">false</use_hetfrz_classnuc>
       <do_prescribed_ccn COMPSET=".*SCREAM.*noAero">false</do_prescribed_ccn>
       <do_predict_nc>true</do_predict_nc>
       <do_predict_nc COMPSET=".*SCREAM.*noAero">false</do_predict_nc>

components/eamxx/src/physics/p3/disp/p3_main_impl_disp.cpp

@@ -257,7 +257,7 @@ ::p3_main_internal_disp(
 
   p3_main_part2_disp(
       nj, nk, runtime_options.max_total_ni, infrastructure.predictNc, infrastructure.prescribedCCN, infrastructure.dt, inv_dt,
-      infrastructure.use_hetfrz_classnuc, hetfrz_immersion_nucleation_tend, hetfrz_contact_nucleation_tend, hetfrz_deposition_nucleation_tend,
+      runtime_options.use_hetfrz_classnuc, hetfrz_immersion_nucleation_tend, hetfrz_contact_nucleation_tend, hetfrz_deposition_nucleation_tend,
       lookup_tables.dnu_table_vals, lookup_tables.ice_table_vals, lookup_tables.collect_table_vals,
       lookup_tables.revap_table_vals, pres, dpres, dz, nc_nuceat_tend, inv_exner,
       exner, inv_cld_frac_l, inv_cld_frac_i, inv_cld_frac_r, ni_activated, inv_qc_relvar, cld_frac_i,

components/eamxx/src/physics/p3/eamxx_p3_process_interface.cpp

@@ -44,7 +44,6 @@ void P3Microphysics::set_grids(const std::shared_ptr<const GridsManager> grids_m
   infrastructure.kte = m_num_levs-1;
   infrastructure.predictNc = m_params.get<bool>("do_predict_nc",true);
   infrastructure.prescribedCCN = m_params.get<bool>("do_prescribed_ccn",true);
-  infrastructure.use_hetfrz_classnuc = m_params.get<bool>("use_hetfrz_classnuc",true);
 
   // Define the different field layouts that will be used for this process
   using namespace ShortFieldTagsNames;

components/eamxx/src/physics/p3/impl/p3_CNT_couple_impl.hpp

@@ -23,8 +23,12 @@ ::CNT_couple(
 {
   constexpr Scalar pi       = C::Pi;
   constexpr Scalar rho_h2o  = C::RHO_H2O;
-  constexpr Scalar qsmall   = 1.0e-18; // BAD_CONSTANT!
+
+  // TODO: Verify if qsmall can be unified with other "small" numeric literals 
+  constexpr Scalar qsmall   = 1.0e-18;
   constexpr Scalar piov3    = pi/3.0;
+
+  // TODO: Verify if 1.0e-18 can be unified with other "small" numeric literals
   constexpr Scalar  mi0     = 4.0*piov3*900.0*1.0e-18; // BAD_CONSTANT!
 
   const Spack Zero(0.0);
@@ -48,6 +52,7 @@ ::CNT_couple(
       qinuc_cnt.set(mask, ninuc_cnt*mi0, Zero);
       break;
     default:
+      EKAT_KERNEL_ERROR_MSG("Error! Unhandled case in switch statement for Iflag in p3_CNT_couple_impl.hpp .\n");
       break;
   }
 }

components/eamxx/src/physics/p3/impl/p3_main_impl.hpp

@@ -248,7 +248,7 @@ ::p3_main_internal(
 
     p3_main_part2(
       team, nk_pack, runtime_options.max_total_ni, infrastructure.predictNc, infrastructure.prescribedCCN, infrastructure.dt, inv_dt,
-      infrastructure.use_hetfrz_classnuc, ohetfrz_immersion_nucleation_tend, ohetfrz_contact_nucleation_tend, ohetfrz_deposition_nucleation_tend,
+      runtime_options.use_hetfrz_classnuc, ohetfrz_immersion_nucleation_tend, ohetfrz_contact_nucleation_tend, ohetfrz_deposition_nucleation_tend,
       lookup_tables.dnu_table_vals, lookup_tables.ice_table_vals, lookup_tables.collect_table_vals, lookup_tables.revap_table_vals, opres, odpres, odz, onc_nuceat_tend, oinv_exner,
       exner, inv_cld_frac_l, inv_cld_frac_i, inv_cld_frac_r, oni_activated, oinv_qc_relvar, ocld_frac_i,
       ocld_frac_l, ocld_frac_r, oqv_prev, ot_prev, T_atm, rho, inv_rho, qv_sat_l, qv_sat_i, qv_supersat_i, rhofacr, rhofaci, acn,

components/eamxx/src/physics/p3/p3_functions.hpp

@@ -134,6 +134,7 @@ struct Functions
     bool set_cld_frac_l_to_one = false;
     bool set_cld_frac_i_to_one = false;
     bool set_cld_frac_r_to_one = false;
+    bool use_hetfrz_classnuc   = false; // Set to true to use het frz from MAM4xx-ACI
 
     void load_runtime_options_from_file(ekat::ParameterList& params) {
       max_total_ni = params.get<double>("max_total_ni", max_total_ni);
@@ -159,6 +160,7 @@ struct Functions
       set_cld_frac_l_to_one = params.get<bool>("set_cld_frac_l_to_one", set_cld_frac_l_to_one);
       set_cld_frac_i_to_one = params.get<bool>("set_cld_frac_i_to_one", set_cld_frac_i_to_one);
       set_cld_frac_r_to_one = params.get<bool>("set_cld_frac_r_to_one", set_cld_frac_r_to_one);
+      use_hetfrz_classnuc   = params.get<bool>("use_hetfrz_classnuc", use_hetfrz_classnuc);
     }
 
   };
@@ -271,8 +273,6 @@ struct Functions
     bool predictNc;
     // Set to true to use prescribed CCN
     bool prescribedCCN;
-    // Set to true to use het frz from MAM4xx-ACI
-    bool use_hetfrz_classnuc;
     // Coordinates of columns, nj x 3
     view_2d<const Scalar> col_location;
   };

components/eamxx/src/physics/p3/tests/infra/p3_test_data.cpp

@@ -1373,7 +1373,7 @@ Int p3_main_host(
                                         precip_ice_surf_d, diag_eff_radius_qc_d, diag_eff_radius_qi_d, diag_eff_radius_qr_d,
                                         rho_qi_d,precip_liq_flux_d, precip_ice_flux_d, precip_total_tend_d, nevapr_d};
   P3F::P3Infrastructure infrastructure{dt, it, its, ite, kts, kte,
-                                       do_predict_nc, do_prescribed_CCN, use_hetfrz_classnuc, col_location_d};
+                                       do_predict_nc, do_prescribed_CCN, col_location_d};
   P3F::P3HistoryOnly history_only{liq_ice_exchange_d, vap_liq_exchange_d,
                                   vap_ice_exchange_d};