Recompute des (snow effective diameter) for radiation in pumas_post_main

Mirrors CAM micro_pumas_cam, including the separate meters-to-microns
conversion step. Match snow diameter standard name with RRTMGP and the
CAM-SIMA registry (snow_crystal).

Author: Haipeng Lin

schemes/pumas/micro_pumas_ccpp_dimensions_post.meta

@@ -528,7 +528,7 @@
   kind = pumas_r8
   intent = in
 [scaled_diam_snow]
-  standard_name = effective_diameter_of_stratiform_snow_particle_for_radiation
+  standard_name = effective_diameter_of_stratiform_snow_crystal_for_radiation
   long_name = snow scaled diameter
   #rrtmgp takes um and the CCPP framework will convert from m
   units = m

schemes/pumas/pumas_post_main.F90

@@ -10,32 +10,35 @@ module pumas_post_main
   !> \section arg_table_pumas_post_main_run Argument Table
   !! \htmlinclude pumas_post_main_run.html
   subroutine pumas_post_main_run(ncol, nlev, trop_cloud_top_lev, rair, pmid, temp, &
-                cldliq, numliq, cldice, numice, graupel, numgraup, strat_cldfrc,   &
-                effi, dei, pgam, lamc, degrau, errmsg, errcode)
+                cldliq, numliq, cldice, numice, snow, numsnow, graupel, numgraup,  &
+                strat_cldfrc, effi, dei, pgam, lamc, des, degrau, errmsg, errcode)
     use ccpp_kinds,        only: kind_phys
     use pumas_kinds,       only: pumas_r8=>kind_r8
     use micro_pumas_utils, only: size_dist_param_basic, size_dist_param_liq, &
                                  mg_ice_props, mg_liq_props, avg_diameter,   &
-                                 mincld, qsmall, rhog, rhows, rhoi
+                                 mincld, qsmall, rhog, rhosn, rhows, rhoi
 
     integer,                 intent(in)  :: ncol
     integer,                 intent(in)  :: nlev
-    integer,                 intent(in)  :: trop_cloud_top_lev !Index of the top model level for which
-                                                               !tropospheric cloud physics is run (index)
+    integer,                 intent(in)  :: trop_cloud_top_lev  ! Index of the top model level for which
+                                                                ! tropospheric cloud physics is run (index)
     real(kind_phys),                 intent(in)  :: rair        ! gas constant of dry air (J kg-1 K-1)
     real(kind_phys), dimension(:,:), intent(in)  :: pmid        ! layer midpoint pressure (Pa)
     real(kind_phys), dimension(:,:), intent(in)  :: temp        ! air temperature, before microphysics heating is applied (K)
     real(kind_phys), dimension(:,:), intent(in)  :: cldliq      ! updated cloud liquid water mixing ratio (kg/kg)
     real(kind_phys), dimension(:,:), intent(in)  :: numliq      ! updated cloud droplet number concentration (kg-1)
     real(kind_phys), dimension(:,:), intent(in)  :: cldice      ! updated cloud ice mixing ratio (kg/kg)
     real(kind_phys), dimension(:,:), intent(in)  :: numice      ! updated cloud ice number concentration (kg-1)
+    real(kind_phys), dimension(:,:), intent(in)  :: snow        ! updated snow mixing ratio (kg/kg)
+    real(kind_phys), dimension(:,:), intent(in)  :: numsnow     ! updated snow number concentration (kg-1)
     real(kind_phys), dimension(:,:), intent(in)  :: graupel     ! updated graupel mixing ratio (kg/kg)
     real(kind_phys), dimension(:,:), intent(in)  :: numgraup    ! updated graupel number concentration (kg-1)
     real(kind_phys), dimension(:,:), intent(in)  :: strat_cldfrc! total stratiform cloud area fraction (= ast)
     real(kind_phys), dimension(:,:), intent(out) :: effi       ! ice effective radius (micron)
     real(kind_phys), dimension(:,:), intent(out) :: dei        ! ice effective diameter for radiation (micron)
     real(kind_phys), dimension(:,:), intent(out) :: pgam       ! droplet size distribution shape parameter for radiation (1)
     real(kind_phys), dimension(:,:), intent(out) :: lamc       ! droplet size distribution slope for radiation (1)
+    real(kind_phys), dimension(:,:), intent(out) :: des        ! snow effective diameter for radiation (micron)
     real(kind_phys), dimension(:,:), intent(out) :: degrau     ! graupel effective diameter for radiation (m)
     character(len=512),          intent(out) :: errmsg
     integer,                 intent(out) :: errcode
@@ -49,6 +52,10 @@ subroutine pumas_post_main_run(ncol, nlev, trop_cloud_top_lev, rair, pmid, temp,
     real(pumas_r8) :: rho(ncol, nlev)      ! air density
     real(pumas_r8) :: mu(ncol, nlev)       ! droplet size distribution shape parameter
     real(pumas_r8) :: lambdac(ncol, nlev)  ! droplet size distribution slope
+    real(pumas_r8) :: qs(ncol, nlev)       ! grid-mean snow mixing ratio
+    real(pumas_r8) :: ns(ncol, nlev)       ! grid-mean snow number conc
+    real(pumas_r8) :: dsout2(ncol, nlev)   ! mean snow particle diameter
+    real(pumas_r8) :: desm(ncol, nlev)     ! snow effective diameter (m)
     real(pumas_r8) :: qg(ncol, nlev)       ! grid-mean graupel mixing ratio
     real(pumas_r8) :: ng(ncol, nlev)       ! grid-mean graupel number conc
     real(pumas_r8) :: dgout2(ncol, nlev)   ! mean graupel particle diameter
@@ -59,7 +66,6 @@ subroutine pumas_post_main_run(ncol, nlev, trop_cloud_top_lev, rair, pmid, temp,
     ! Ice effective radius is recomputed here from the post-microphysics
     ! grid-mean in-cloud ice, NOT from the raw per-substep value PUMAS returns.
     ! PUMAS uses the total stratiform fraction for ice cloud (icecldf = ast).
-    ! Mirrors CAM micro_pumas_cam.F90:2677 (icimrst), :3174 (niic), :3171-3193 (rei).
     icimrst(:,:) = min(real(cldice(:ncol,:), pumas_r8) / &
                 max(mincld, real(strat_cldfrc(:ncol,:), pumas_r8)), 0.005_pumas_r8)
     niic(:,:)   =    real(numice(:ncol,:), pumas_r8) / &
@@ -79,16 +85,16 @@ subroutine pumas_post_main_run(ncol, nlev, trop_cloud_top_lev, rair, pmid, temp,
     effi(:ncol,:) = real(rei(:,:), kind_phys)
 
     ! Ice effective diameter for radiation follows from the recomputed
-    ! effective radius. Mirrors CAM micro_pumas_cam.F90:3080 (dei).
+    ! effective radius.
     dei(:ncol,:) = real(rei(:,:) * rhoi/rhows * 2._pumas_r8, kind_phys)
 
     ! Droplet size distribution parameters for radiation are likewise recomputed
-    ! from the post-microphysics grid-mean in-cloud liquid. Air density uses the
-    ! temperature BEFORE the microphysics heating is applied (in CAM the input
-    ! state, not the substepped local state, "to preserve answers").
-    ! PUMAS uses the total stratiform fraction for liquid cloud (liqcldf = ast).
-    ! Mirrors CAM micro_pumas_cam.F90:2919 (rho), :2621 (icwmrst), :2957 (ncic),
-    ! :2952-2978 (mu, lambdac).
+    ! from the post-microphysics grid-mean in-cloud liquid.
+    ! Air density uses the temperature BEFORE the microphysics heating is applied
+    ! The original comment in CAM noted:
+    !   "State instead of state_loc to preserve answers for MG1 (and in any
+    !    case, it is unlikely to make much difference)."
+    ! PUMAS uses the total stratiform fraction for liquid cloud (liqcldf = ast)
     rho(:,:)     = real(pmid(:ncol,:), pumas_r8) / &
                 (real(rair, pumas_r8) * real(temp(:ncol,:), pumas_r8))
     icwmrst(:,:) = min(real(cldliq(:ncol,:), pumas_r8) / &
@@ -103,17 +109,32 @@ subroutine pumas_post_main_run(ncol, nlev, trop_cloud_top_lev, rair, pmid, temp,
                                mu(:,k), lambdac(:,k), ncol)
     end do
 
-    ! size_dist_param_liq flags no-cloud points with mu = -100; CAM resets
-    ! those to zero (lambdac is already zero there).
+    ! size_dist_param_liq flags no-cloud points with mu = -100 and reset to zero.
     where (icwmrst(:,trop_cloud_top_lev:) < qsmall)
       mu(:,trop_cloud_top_lev:) = 0._pumas_r8
     end where
 
     pgam(:ncol,:) = real(mu(:,:), kind_phys)
     lamc(:ncol,:) = real(lambdac(:,:), kind_phys)
 
-    ! Graupel effective diameter for radiation, from the post-microphysics
-    ! grid-mean graupel. Mirrors CAM micro_pumas_cam.F90:3043-3056 (degrau).
+    ! Snow effective diameter for radiation, from the post-microphysics grid-mean snow
+    qs(:,:) = real(snow(:ncol,:), pumas_r8)
+    ns(:,:) = real(numsnow(:ncol,:), pumas_r8)
+
+    dsout2(:,:) = 0._pumas_r8
+    desm(:,:)   = 0._pumas_r8
+    where (qs(:,trop_cloud_top_lev:) >= 1.e-7_pumas_r8)
+      dsout2(:,trop_cloud_top_lev:) = avg_diameter( &
+           qs(:,trop_cloud_top_lev:), &
+           ns(:,trop_cloud_top_lev:) * rho(:,trop_cloud_top_lev:), &
+           rho(:,trop_cloud_top_lev:), rhosn)
+      desm(:,trop_cloud_top_lev:) = dsout2(:,trop_cloud_top_lev:) * &
+           3._pumas_r8 * rhosn/rhows
+    end where
+
+    des(:ncol,:) = real(desm(:,:) * 1.e6_pumas_r8, kind_phys)
+
+    ! Graupel effective diameter for radiation, from the post-microphysics grid-mean graupel
     qg(:,:) = real(graupel(:ncol,:), pumas_r8)
     ng(:,:) = real(numgraup(:ncol,:), pumas_r8)
 

schemes/pumas/pumas_post_main.meta

@@ -87,6 +87,24 @@
   kind = kind_phys
   intent = in
   advected = true
+[snow]
+  standard_name = snow_mixing_ratio_wrt_moist_air_and_condensed_water
+  long_name = snow mixing ratio wrt moist air and condensed water
+  units = kg kg-1
+  dimensions = (horizontal_loop_extent, vertical_layer_dimension)
+  type = real
+  kind = kind_phys
+  intent = in
+  advected = true
+[numsnow]
+  standard_name = mass_number_concentration_of_snow_crystals_in_moist_air_and_condensed_water
+  long_name = mass number concentration of snow wrt moist air and condensed water
+  units = kg-1
+  dimensions = (horizontal_loop_extent, vertical_layer_dimension)
+  type = real
+  kind = kind_phys
+  intent = in
+  advected = true
 [graupel]
   standard_name = graupel_water_mixing_ratio_wrt_moist_air_and_condensed_water
   long_name = graupel mixing ratio wrt moist air and condensed water
@@ -145,6 +163,14 @@
   type = real
   kind = kind_phys
   intent = out
+[des]
+  standard_name = effective_diameter_of_stratiform_snow_crystal_for_radiation
+  long_name = effective diameter of stratiform snow particles for radiation
+  units = um
+  dimensions = (horizontal_loop_extent, vertical_layer_dimension)
+  type = real
+  kind = kind_phys
+  intent = out
 [degrau]
   standard_name = effective_diameter_of_stratiform_cloud_graupel_particle_for_radiation
   long_name = effective diameter of stratiform graupel particles for radiation