Changeset 2946 for LMDZ5/trunk/libf/phylmd/fonte_neige_mod.F90

Timestamp:

Jul 12, 2017, 8:28:32 PM (8 years ago)

Author:

oboucher

Message:

Put under the ok_lic_cond flag the option of depositing water vapour
onto snow, especially over ice sheets (lic). The default for the flag is
FALSE in order to keep backward compatibility, but should be turned to TRUE
in order to close the water budget. Tested in CM6.0.11.

File:

• LMDZ5/trunk/libf/phylmd/fonte_neige_mod.F90 (modified) (4 diffs)

LMDZ5/trunk/libf/phylmd/fonte_neige_mod.F90

@@ -213 +213 @@
 
     snow_evap = 0.
-    WHERE (evap > 0. ) 
-       snow_evap = MIN (snow / dtime, evap) 
-       snow = snow - snow_evap * dtime
-       snow = MAX(0.0, snow)
-    END WHERE
+  
+    IF (.NOT. ok_lic_cond) THEN
+!---only positive evaporation has an impact on snow 
+!---note that this could create a bit of water
+!---this was the default until CMIP6 
+      WHERE (evap > 0. )
+         snow_evap = MIN (snow / dtime, evap)    !---one cannot evaporate more than the amount of snow
+         snow = snow - snow_evap * dtime         !---snow that remains on the ground
+         snow = MAX(0.0, snow)                   !---just in case
+      END WHERE
+    ELSE
+!--now considers both positive and negative evaporation in the budget of snow 
+      snow_evap = MIN (snow / dtime, evap)    !---one cannot evaporate more than the amount of snow
+      snow = snow - snow_evap * dtime         !---snow that remains or deposits on the ground
+      snow = MAX(0.0, snow)                   !---just in case
+   ENDIF
     
     bil_eau_s(:) = (precip_rain(:) * dtime) - (evap(:) - snow_evap(:)) * dtime
@@ -232 +243 @@
     fqcalving(:) = 0.0
     fqfonte(:) = 0.0
+
     DO i = 1, knon
        ! Y'a-t-il fonte de neige?
-       neige_fond = ((snow(i) > epsfra .OR. nisurf == is_sic .OR. nisurf == is_lic) &
-            .AND. tsurf_new(i) >= RTT)
+       neige_fond = (snow(i)>epsfra .OR. nisurf==is_sic .OR. nisurf==is_lic) .AND. tsurf_new(i)>=RTT
        IF (neige_fond) THEN
           fq_fonte     = MIN( MAX((tsurf_new(i)-RTT )/chasno,0.0),snow(i))
@@ -258 +269 @@
        ENDIF
 
-       ! s'il y a une hauteur trop importante de neige, elle s'coule
+       ! s'il y a une hauteur trop importante de neige, elle est ecretee
        fqcalving(i) = MAX(0., snow(i) - snow_max)/dtime
        snow(i)=MIN(snow(i),snow_max)
-    END DO
-
+    ENDDO
 
     IF (nisurf == is_ter) THEN
@@ -269 +279 @@
           run_off_ter(i) = run_off_ter(i) + MAX(qsol(i) - max_eau_sol, 0.0)
           qsol(i) = MIN(qsol(i), max_eau_sol) 
-       END DO
+       ENDDO
     ELSE IF (nisurf == is_lic) THEN
        DO i = 1, knon
           j = knindex(i)
-          run_off_lic(i)   = (coeff_rel *  fqcalving(i)) + &
-               (1. - coeff_rel) * run_off_lic_0(j)
+          !--temporal filtering
+          run_off_lic(i)   = coeff_rel*fqcalving(i) + (1.-coeff_rel)*run_off_lic_0(j)
           run_off_lic_0(j) = run_off_lic(i)
+          !--add melting snow and liquid precip to runoff of ice cap
           run_off_lic(i)   = run_off_lic(i) + fqfonte(i) + precip_rain(i)
-       END DO
+       ENDDO
     ENDIF