add runtime flag for p3 ice production

components/eamxx/cime_config/namelist_defaults_scream.xml

@@ -214,6 +214,7 @@ be lost if SCREAM_HACK_XML is not enabled.
       <p3_dep_nucleation_exponent type="real" doc="P3 dep_nucleation_exponent (deposition nucleation)">0.304</p3_dep_nucleation_exponent>
       <p3_ice_sed_knob type="real" doc="P3 ice_sed_knob (ice fall speed)">1.0</p3_ice_sed_knob>
       <p3_d_breakup_cutoff type="real" doc="P3 d_breakup_cutoff (rain self collection and breakup)">0.00028</p3_d_breakup_cutoff>
+      <p3_do_ice_production type="logical" doc="Flag to turn on ice production processes in P3 (loss processes unaffected by this flag)">true</p3_do_ice_production>
     </p3>
 
     <!-- SHOC macrophysics -->

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

@@ -123,6 +123,8 @@ ::p3_main_internal_disp(
   const     Int    kbot         = kdir == -1 ? nk-1 : 0;
   constexpr bool   debug_ABORT  = false;
 
+  const bool do_ice_production = runtime_options.p3_do_ice_production;
+
   // per-column bools
   view_1d<bool> nucleationPossible("nucleationPossible", nj);
   view_1d<bool> hydrometeorsPresent("hydrometeorsPresent", nj);
@@ -294,9 +296,11 @@ ::p3_main_internal_disp(
       lookup_tables.ice_table_vals, diagnostic_outputs.precip_ice_surf, nucleationPossible, hydrometeorsPresent, runtime_options);
 
   // homogeneous freezing f cloud and rain
-  homogeneous_freezing_disp(
-      T_atm, inv_exner, nj, nk, ktop, kbot, kdir, qc, nc, qr, nr, qi,
-      ni, qm, bm, th, nucleationPossible, hydrometeorsPresent);
+  if(do_ice_production) {
+    homogeneous_freezing_disp(T_atm, inv_exner, nj, nk, ktop, kbot, kdir, qc,
+                              nc, qr, nr, qi, ni, qm, bm, th,
+                              nucleationPossible, hydrometeorsPresent);
+  }
 
   //
   // final checks to ensure consistency of mass/number
@@ -334,4 +338,3 @@ ::p3_main_internal_disp(
 
 } // namespace p3
 } // namespace scream
-

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

@@ -233,6 +233,7 @@ void P3Microphysics::initialize_impl (const RunType /* run_type */)
   runtime_options.p3_dep_nucleation_exponent = m_params.get<double>("p3_dep_nucleation_exponent", 0.304);
   runtime_options.p3_ice_sed_knob = m_params.get<double>("p3_ice_sed_knob", 1.0);
   runtime_options.p3_d_breakup_cutoff = m_params.get<double>("p3_d_breakup_cutoff", 0.00028);
+  runtime_options.p3_do_ice_production = m_params.get<bool>("p3_do_ice_production", true);
 
   // Set property checks for fields in this process
   add_invariant_check<FieldWithinIntervalCheck>(get_field_out("T_mid"),m_grid,100.0,500.0,false);

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

@@ -99,6 +99,8 @@ ::p3_main_internal(
   const     Int    kbot         = kdir == -1 ? nk-1 : 0;
   constexpr bool   debug_ABORT  = false;
 
+  const bool do_ice_production = runtime_options.p3_do_ice_production;
+
   // we do not want to measure init stuff
   auto start = std::chrono::steady_clock::now();
 
@@ -287,9 +289,10 @@ ::p3_main_internal(
       lookup_tables.ice_table_vals, diagnostic_outputs.precip_ice_surf(i), runtime_options);
 
     // homogeneous freezing of cloud and rain
-    homogeneous_freezing(
-      T_atm, oinv_exner, team, nk, ktop, kbot, kdir, oqc, onc, oqr, onr, oqi,
-      oni, oqm, obm, oth);
+    if(do_ice_production) {
+      homogeneous_freezing(T_atm, oinv_exner, team, nk, ktop, kbot, kdir, oqc,
+                           onc, oqr, onr, oqi, oni, oqm, obm, oth);
+    }
 
     //
     // final checks to ensure consistency of mass/number

components/eamxx/src/physics/p3/impl/p3_main_impl_part2.hpp

@@ -104,6 +104,8 @@ ::p3_main_part2(
   constexpr Scalar latvap       = C::LatVap;
   constexpr Scalar latice       = C::LatIce;
 
+  const bool do_ice_production = runtime_options.p3_do_ice_production;
+
   team.team_barrier();
   hydrometeorsPresent = false;
   team.team_barrier();
@@ -266,61 +268,77 @@ ::p3_main_part2(
       // ice processes
       // ......................................................................
 
-      // collection of droplets
-      ice_cldliq_collection(
-        rho(k), T_atm(k), rhofaci(k), table_val_qc2qi_collect, qi_incld(k), qc_incld(k), ni_incld(k), nc_incld(k),
-        qc2qi_collect_tend, nc_collect_tend, qc2qr_ice_shed_tend, ncshdc, runtime_options, not_skip_micro);
-
-      // collection of rain
-      ice_rain_collection(
-        rho(k), T_atm(k), rhofaci(k), logn0r(k), table_val_nr_collect, table_val_qr2qi_collect, qi_incld(k), ni_incld(k), qr_incld(k),
-        qr2qi_collect_tend, nr_collect_tend, runtime_options, not_skip_micro);
-
-      // collection between ice categories
-
-      // PMC nCat deleted lots of stuff here.
-
-      // self-collection of ice
-      ice_self_collection(
-        rho(k), rhofaci(k), table_val_ni_self_collect, eii, qm_incld(k), qi_incld(k), ni_incld(k),
-        ni_selfcollect_tend, not_skip_micro);
+      if(do_ice_production) {
+        // collection of droplets
+        ice_cldliq_collection(rho(k), T_atm(k), rhofaci(k),
+                              table_val_qc2qi_collect, qi_incld(k), qc_incld(k),
+                              ni_incld(k), nc_incld(k), qc2qi_collect_tend,
+                              nc_collect_tend, qc2qr_ice_shed_tend, ncshdc,
+                              runtime_options, not_skip_micro);
+
+        // collection of rain
+        ice_rain_collection(rho(k), T_atm(k), rhofaci(k), logn0r(k),
+                            table_val_nr_collect, table_val_qr2qi_collect,
+                            qi_incld(k), ni_incld(k), qr_incld(k),
+                            qr2qi_collect_tend, nr_collect_tend,
+                            runtime_options, not_skip_micro);
+
+        // collection between ice categories
+
+        // PMC nCat deleted lots of stuff here.
+
+        // self-collection of ice
+        ice_self_collection(rho(k), rhofaci(k), table_val_ni_self_collect, eii,
+                            qm_incld(k), qi_incld(k), ni_incld(k),
+                            ni_selfcollect_tend, not_skip_micro);
+      }
 
       // melting
-      ice_melting(
-        rho(k), T_atm(k), pres(k), rhofaci(k), table_val_qi2qr_melting, table_val_qi2qr_vent_melt, dv, sc, mu, kap, qv(k), qi_incld(k), ni_incld(k),
-        qi2qr_melt_tend, ni2nr_melt_tend, not_skip_micro);
-
-      // calculate wet growth
-      ice_cldliq_wet_growth(
-        rho(k), T_atm(k), pres(k), rhofaci(k), table_val_qi2qr_melting, table_val_qi2qr_vent_melt,
-        dv, kap, mu, sc, qv(k), qc_incld(k), qi_incld(k), ni_incld(k), qr_incld(k),
-        wetgrowth, qr2qi_collect_tend, qc2qi_collect_tend, qc_growth_rate, nr_ice_shed_tend, qc2qr_ice_shed_tend, not_skip_micro);
-
-      // calculate total inverse ice relaxation timescale combined for all ice categories
-      // note 'f1pr' values are normalized, so we need to multiply by N
+      ice_melting(rho(k), T_atm(k), pres(k), rhofaci(k),
+                  table_val_qi2qr_melting, table_val_qi2qr_vent_melt, dv, sc,
+                  mu, kap, qv(k), qi_incld(k), ni_incld(k), qi2qr_melt_tend,
+                  ni2nr_melt_tend, not_skip_micro);
+
+      if(do_ice_production) {
+        // calculate wet growth
+        ice_cldliq_wet_growth(
+            rho(k), T_atm(k), pres(k), rhofaci(k), table_val_qi2qr_melting,
+            table_val_qi2qr_vent_melt, dv, kap, mu, sc, qv(k), qc_incld(k),
+            qi_incld(k), ni_incld(k), qr_incld(k), wetgrowth,
+            qr2qi_collect_tend, qc2qi_collect_tend, qc_growth_rate,
+            nr_ice_shed_tend, qc2qr_ice_shed_tend, not_skip_micro);
+      }
+
+      // calculate total inverse ice relaxation timescale combined for all ice
+      // categories note 'f1pr' values are normalized, so we need to multiply
+      // by N
       ice_relaxation_timescale(
-        rho(k), T_atm(k), rhofaci(k), table_val_qi2qr_melting, table_val_qi2qr_vent_melt, dv, mu, sc, qi_incld(k), ni_incld(k),
-        epsi, epsi_tot, not_skip_micro);
+          rho(k), T_atm(k), rhofaci(k), table_val_qi2qr_melting,
+          table_val_qi2qr_vent_melt, dv, mu, sc, qi_incld(k), ni_incld(k), epsi,
+          epsi_tot, not_skip_micro);
 
       // calculate rime density
-      calc_rime_density(
-        T_atm(k), rhofaci(k), table_val_qi_fallspd, acn(k), lamc(k), mu_c(k), qc_incld(k), qc2qi_collect_tend,
-        vtrmi1, rho_qm_cloud, not_skip_micro);
-
-      // contact and immersion freezing droplets
-      cldliq_immersion_freezing(
-        T_atm(k), lamc(k), mu_c(k), cdist1(k), qc_incld(k), inv_qc_relvar(k),
-        qc2qi_hetero_freeze_tend, nc2ni_immers_freeze_tend, runtime_options, not_skip_micro);
-
-      // for future: get rid of log statements below for rain freezing
-      rain_immersion_freezing(
-        T_atm(k), lamr(k), mu_r(k), cdistr(k), qr_incld(k),
-        qr2qi_immers_freeze_tend, nr2ni_immers_freeze_tend, runtime_options, not_skip_micro);
-
-      //  rime splintering (Hallet-Mossop 1974)
-      // PMC comment: Morrison and Milbrandt 2015 part 1 and 2016 part 3 both say
-      // that Hallet-Mossop should be neglected if 1 category to compensate for
-      // artificial smearing out of ice DSD
+      calc_rime_density(T_atm(k), rhofaci(k), table_val_qi_fallspd, acn(k),
+                        lamc(k), mu_c(k), qc_incld(k), qc2qi_collect_tend,
+                        vtrmi1, rho_qm_cloud, not_skip_micro);
+
+      if(do_ice_production) {
+        // contact and immersion freezing droplets
+        cldliq_immersion_freezing(
+            T_atm(k), lamc(k), mu_c(k), cdist1(k), qc_incld(k),
+            inv_qc_relvar(k), qc2qi_hetero_freeze_tend,
+            nc2ni_immers_freeze_tend, runtime_options, not_skip_micro);
+
+        // for future: get rid of log statements below for rain freezing
+        rain_immersion_freezing(T_atm(k), lamr(k), mu_r(k), cdistr(k),
+                                qr_incld(k), qr2qi_immers_freeze_tend,
+                                nr2ni_immers_freeze_tend, runtime_options,
+                                not_skip_micro);
+        //  rime splintering (Hallet-Mossop 1974)
+        // PMC comment: Morrison and Milbrandt 2015 part 1 and 2016 part 3 both
+        // say that Hallet-Mossop should be neglected if 1 category to
+        // compensate for artificial smearing out of ice DSD
+      }
 
       // ................................................
       //  condensation/evaporation/deposition/sublimation
@@ -336,15 +354,22 @@ ::p3_main_part2(
 		     ab,abi,epsr,epsi_tot,T_atm(k),t_prev(k),dqsdt,dt,
 		     qr2qv_evap_tend,nr_evap_tend, not_skip_micro);
 
-      ice_deposition_sublimation(
-	qi_incld(k), ni_incld(k), T_atm(k), qv_sat_l(k), qv_sat_i(k), epsi, abi, qv(k), inv_dt,
-        qv2qi_vapdep_tend, qi2qv_sublim_tend, ni_sublim_tend, qc2qi_berg_tend, not_skip_micro);
+      if(do_ice_production) {
+        ice_deposition_sublimation(
+            qi_incld(k), ni_incld(k), T_atm(k), qv_sat_l(k), qv_sat_i(k), epsi,
+            abi, qv(k), inv_dt, qv2qi_vapdep_tend, qi2qv_sublim_tend,
+            ni_sublim_tend, qc2qi_berg_tend, not_skip_micro);
+      }
+
     }
 
     // deposition/condensation-freezing nucleation
-    ice_nucleation(
-      T_atm(k), inv_rho(k), ni(k), ni_activated(k), qv_supersat_i(k), inv_dt, predictNc, do_prescribed_CCN,
-      qv2qi_nucleat_tend, ni_nucleat_tend, runtime_options, not_skip_all);
+    if(do_ice_production) {
+      ice_nucleation(T_atm(k), inv_rho(k), ni(k), ni_activated(k),
+                     qv_supersat_i(k), inv_dt, predictNc, do_prescribed_CCN,
+                     qv2qi_nucleat_tend, ni_nucleat_tend, runtime_options,
+                     not_skip_all);
+    }
 
     // cloud water autoconversion
     // NOTE: cloud_water_autoconversion must be called before droplet_self_collection

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

@@ -122,6 +122,7 @@ struct Functions
     Scalar p3_dep_nucleation_exponent = 0.304;
     Scalar p3_ice_sed_knob = 1.0;
     Scalar p3_d_breakup_cutoff = 0.00028;
+    bool p3_do_ice_production = true;
   };
 
   // This struct stores prognostic variables evolved by P3.