Wip on adding prescribed cloud droplet number concentration

config/default_configs/default_config.yml

@@ -193,6 +193,9 @@ apply_limiter:
 precip_model:
   help: "Precipitation model [`nothing` (default), `0M`]"
   value: ~
+prescribed_Nd:
+  help: "Prescribed number concentration of cloud droplets per cubic meter of air. If set to zero the scheme uses 1-moment autoconversion rate that does not depend on Nd [`nothing` (default), any positive number]"
+  value: ~
 cloud_model:
   help: "Cloud model [`grid_scale`, `quadrature` (default), `diagnostic_edmfx`]"
   value: "quadrature"

src/parameterized_tendencies/microphysics/microphysics_wrappers.jl

@@ -129,6 +129,25 @@ function e_tot_0M_precipitation_sources_helper(
     return λ * Iₗ(thp, ts) + (1 - λ) * Iᵢ(thp, ts) + Φ
 end
 
+"""
+    rain_autoconversion_helper(mp, thp, ts, ρ)
+
+ - mp - 1-moment microphysics parameters
+ - thermodynamics parameters
+ - thermodynamic state
+ - air density
+
+Returns rain autoconversion rate based on the 1-moment microphysics scheme
+  or on the 2-moment microphysics scheme with prescribed number concentration
+  of cloud droplets.
+"""
+function rain_autoconversion_helper(mp, thp, ts, ρ)
+    return
+        isnothing(mp.Ndp) ?
+        CM1.conv_q_liq_to_q_rai(mp.pr.acnv1M, qₗ(thp, ts), true) :
+        CM2.conv_q_liq_to_q_rai(mp.vrt, qₗ(thp, ts), ρ, mp.Ndp)
+end
+
 """
     compute_precipitation_sources!(Sᵖ, Sᵖ_snow, Sqₜᵖ, Sqᵣᵖ, Sqₛᵖ, Seₜᵖ, ρ, qᵣ, qₛ, ts, Φ, dt, mp, thp)
 
@@ -174,7 +193,7 @@ function compute_precipitation_sources!(
     # rain autoconversion: q_liq -> q_rain
     @. Sᵖ = min(
         limit(qₗ(thp, ts), dt, 5),
-        CM1.conv_q_liq_to_q_rai(mp.pr.acnv1M, qₗ(thp, ts), true),
+        rain_autoconversion_helper(mp, thp, ts, ρ)
     )
     @. Sqₜᵖ -= Sᵖ
     @. Sqᵣᵖ += Sᵖ

src/parameters/create_parameters.jl

@@ -82,6 +82,7 @@ function create_parameter_set(config::AtmosConfig)
             FT(CA.time_to_seconds(parsed_args["dt"]))
     end
     precip_model = parsed_args["precip_model"]
+    prescribed_Nd = parsed_args["prescribed_Nd"]
     microphysics_precipitation_params =
         if precip_model == nothing || precip_model == "nothing"
             nothing
@@ -96,6 +97,8 @@ function create_parameter_set(config::AtmosConfig)
                 ce = CM.Parameters.CollisionEff(toml_dict),
                 tv = CM.Parameters.Blk1MVelType(toml_dict),
                 aps = CM.Parameters.AirProperties(toml_dict),
+                var = CM.Parameters.VarTimescaleAcnv(toml_dict),
+                Ndp = prescribed_Nd == 0 ? nothing : FT(prescribed_Nd),
             )
         else
             error("Invalid precip_model $(precip_model)")