Changeset 3268 for trunk/LMDZ.GENERIC

Timestamp:

Mar 14, 2024, 9:32:34 AM (8 months ago)

Author:

mturbet

Message:

changes in computation of snow albedo when ok_slab_ocean is activated

Location:

trunk/LMDZ.GENERIC

Files:

• changelog.txt (modified) (1 diff)
• libf/phystd/hydrol.F90 (modified) (3 diffs)
• libf/phystd/ocean_slab_mod.F90 (modified) (1 diff)
• libf/phystd/physiq_mod.F90 (modified) (3 diffs)

trunk/LMDZ.GENERIC/changelog.txt

@@ -1881 +1881 @@
 conditions for the presence of solar flux. 
 
-== 13/03/2024 == MT
+== 13-14/03/2024 == MT
 
 - Very minor change of max sea ice fraction in ocean model
 - Preliminary cleanup+commenting in hydrol.F90
+- Changes in computation of snow albedo when ok_slab_ocean is activated

trunk/LMDZ.GENERIC/libf/phystd/hydrol.F90

@@ -15 +15 @@
   USE tracer_h
 !  use slab_ice_h
-  USE ocean_slab_mod, ONLY: alb_ice_max
-  USE ocean_slab_mod, ONLY: alb_ice_min
-  USE ocean_slab_mod, ONLY: h_alb_ice
+  USE ocean_slab_mod, ONLY: alb_ice_max,alb_ice_min,h_alb_ice,snow_min
   use callkeys_mod, only: albedosnow,alb_ocean,albedoco2ice,ok_slab_ocean,Tsaldiff,maxicethick,co2cond
   use radinc_h, only : L_NSPECTV
@@ -102 +100 @@
       real ztsurf(ngrid)
       real albedo_sic, alb_ice
-      real zfra
+      real frac_snow
 
       integer, save :: ivap, iliq, iice
@@ -221 +219 @@
             if(ok_slab_ocean) then ! if ocean heat transport param activated
           
-               zfra = MAX(0.0,MIN(1.0,zqsurf(ig,iice)/45.0))     ! Snow Fraction (Critical height 45kg/m2~15cm)
-               alb_ice=alb_ice_max-(alb_ice_max-alb_ice_min) &   ! Ice Albedo
+               frac_snow = MAX(0.0,MIN(1.0,zqsurf(ig,iice)/snow_min)) ! Critical snow height (in kg/m2) from ocean_slab_ice routine. 
+               ! Standard value should be 15kg/m2 (i.e. about 5 cm). Note that in the previous ocean param. (from BC2014), this value was 45kg/m2 (i.e. about 15cm).
+               alb_ice=alb_ice_max-(alb_ice_max-alb_ice_min) & ! Ice Albedo
                *exp(-sea_ice(ig)/h_alb_ice)
                ! Albedo final calculation :
                do nw=1,L_NSPECTV
                   albedo(ig,nw) = pctsrf_sic(ig)*                                        &
-                                 (albedo_snow_SPECTV(nw)*zfra + alb_ice*(1.0-zfra))      &
+                                 (albedo_snow_SPECTV(nw)*frac_snow + alb_ice*(1.0-frac_snow))      &
                                + (1.-pctsrf_sic(ig))*alb_ocean
                enddo

trunk/LMDZ.GENERIC/libf/phystd/ocean_slab_mod.F90

@@ -112 +112 @@
 
 ! control of snow and ice cover & freeze / melt (heights in m converted to kg/m2)
-    REAL, PARAMETER :: snow_min=0.05*sno_den ! critical snow height [in kg/m2]
+    REAL, PARAMETER, PUBLIC :: snow_min=0.05*sno_den ! critical snow height [in kg/m2]
     REAL, PARAMETER :: snow_wfact=0.4 ! max fraction of falling snow blown into ocean [in kg/m2]
     REAL, PARAMETER :: ice_frac_min=0.001

trunk/LMDZ.GENERIC/libf/phystd/physiq_mod.F90

@@ -1928 +1928 @@
             enddo
 
+!! These two commented functions are from BC2014 (only kept for record)
+!!
 !!            call ocean_slab_ice(ptimestep,                          &
 !!                                ngrid, knindex, tsea_ice, fluxrad,  &
@@ -1934 +1936 @@
 !!                                flux_sens_lat,tsea_ice, pctsrf_sic, &
 !!                               taux,tauy,icount)
-
-
 !!            call ocean_slab_get_vars(ngrid,tslab,      &
 !!                                     sea_ice, flux_o,  &
@@ -1955 +1955 @@
             call ocean_slab_get_vars(ngrid, tslab, sea_ice, flux_g, &
                       dt_hdiff, dt_ekman)
+                      
+!! sea_ice defines the sea ice thickness in kg/m2
+!! pctsrf_sic defines the percentage of the oceanic grid that is covered by sea ice (between 0 and **almost** 1)
+!! qsurf(:,igcm_h2o_ice) defines the amount of snow that accumulates on top of the sea ice (in kg/m2) ; note that the snow fraction depends on the amount of snow.
+!! therefore, beware that qsurf(:,igcm_h2o_ice) has its own meaning for oceanic grid points (when ok_slab_ocean activated)
+
 
             do ig=1,ngrid