Changeset 5496 for LMDZ6

Timestamp:

Jan 20, 2025, 10:37:37 PM (28 hours ago)

Author:

evignon

Message:

nouvelle option pour le calcul du rayon optique des cristaux de glace nuageuse
qui inclue une dependance en temperature ET en contenu en glace (contrairement a la formule
utilisee aujourdhui qui n'a qu'une dependance en T) La formule derivee ici est relativement simple
avec deux coefficients de tuning dont les plages de valeurs acceptables sont donnes en commentaires.
Elle se compare tres bien avec la formule " de reference " de Sun and Rikkus 1999 et Sun 2001

Location:

LMDZ6/trunk/libf/phylmd

Files:

• lmdz_cloud_optics_prop.f90 (modified) (3 diffs)
• lmdz_cloud_optics_prop_ini.f90 (modified) (3 diffs)

LMDZ6/trunk/libf/phylmd/lmdz_cloud_optics_prop.f90

@@ -27 +27 @@
   USE lmdz_cloud_optics_prop_ini , ONLY : rad_chau1, rad_chau2, rad_froid, iflag_rei
   USE lmdz_cloud_optics_prop_ini , ONLY : ok_icefra_lscp, rei_max, rei_min
+  USE lmdz_cloud_optics_prop_ini , ONLY : rei_coef, rei_min_temp
   USE lmdz_cloud_optics_prop_ini , ONLY : zepsec, novlp, iflag_ice_thermo, ok_new_lscp
   
@@ -300 +301 @@
           zfiwp_var = 1000.*icefrac_optics(i, k)*radocond(i, k)/pclc(i, k)*rhodz(i, k)
           ! Calculation of ice cloud effective radius in micron
-          IF (iflag_rei .EQ. 1) THEN
+          IF (iflag_rei .EQ. 2) THEN
+            ! in-cloud ice water content in g/m3
+            iwc = icefrac_optics(i,k) * radocond(i,k) / pclc(i,k) * zrho(i,k) * 1000.
+            ! this formula is a simplified version of the Sun 2001 one (as in the IFS model,
+            ! and which is activated for iflag_rei = 1).
+            ! In particular, the term in temperature**2 has been simplified.
+            ! The new coefs are tunable, and are by default set so that the results fit well
+            ! to the Sun 2001 formula
+            ! By default, rei_coef = 2.4 and rei_min_temp = 175.
+            ! The ranges of these parameters are determined so that the RMSE between this
+            ! formula and the one from Sun 2001 is less than 4 times the minimum RMSE
+            ! The ranges are [1.9, 2.9] for rei_coef and [160., 185.] for rei_min_temp
+            dei = rei_coef * (iwc**0.2445) * ( temp(i,k) - rei_min_temp )
+            ! we clip the results
+            deimax = 20.
+            deimin = 155.
+            dei = MIN(MAX(dei, deimin), deimax)
+            ! formula to convert effective diameter in effective radius
+            rei = 3. * SQRT(3.) / 8. * dei
+          ELSEIF (iflag_rei .EQ. 1) THEN
             ! when we account for precipitation in the radiation scheme,
             ! It is recommended to use the rei formula from Sun and Rikkus 1999 with a revision
@@ -407 +427 @@
 
 
-        IF (iflag_rei .GT. 0) THEN
-
+        IF (iflag_rei .EQ. 2) THEN
+            ! in-cloud ice water content in g/m3
+            iwc = icefrac_optics(i,k) * radocond(i,k) / pclc(i,k) * zrho(i,k) * 1000.
+            ! this formula is a simplified version of the Sun 2001 one (as in the IFS model,
+            ! and which is activated for iflag_rei = 1).
+            ! In particular, the term in temperature**2 has been simplified.
+            ! The new coefs are tunable, and are by default set so that the results fit well
+            ! to the Sun 2001 formula
+            ! By default, rei_coef = 2.4 and rei_min_temp = 175.
+            ! The ranges of these parameters are determined so that the RMSE between this
+            ! formula and the one from Sun 2001 is less than 4 times the minimum RMSE
+            ! The ranges are [1.9, 2.9] for rei_coef and [160., 185.] for rei_min_temp
+            dei = rei_coef * (iwc**0.2445) * ( temp(i,k) - rei_min_temp )
+            ! we clip the results
+            deimin = 20.
+            deimin = 155.
+            dei = MIN(MAX(dei, deimin), deimax)
+            ! formula to convert effective diameter to effective radius
+            rei = 3. * SQRT(3.) / 8. * dei
+
+        ELSEIF (iflag_rei .EQ. 1) THEN
             ! when we account for precipitation in the radiation scheme,
             ! we use the rei formula from Sun and Rikkus 1999 with a revision

LMDZ6/trunk/libf/phylmd/lmdz_cloud_optics_prop_ini.f90

@@ -21 +21 @@
   REAL, PROTECTED :: rad_chau1, rad_chau2, rad_froid
   REAL, PROTECTED :: rei_max, rei_min
+  REAL, PROTECTED :: rei_coef, rei_min_temp
   REAL, PROTECTED :: zepsec
   REAL, PARAMETER :: thres_tau=0.3, thres_neb=0.001
@@ -38 +39 @@
 !$OMP THREADPRIVATE(cdnc_min, cdnc_min_m3, rpi, rg, rd)
 !$OMP THREADPRIVATE(rad_chau1, rad_chau2, rad_froid, rei_max, rei_min)
+!$OMP THREADPRIVATE(rei_coef, rei_min_temp)
 !$OMP THREADPRIVATE(zepsec) 
 
@@ -98 +100 @@
     rei_max = 61.29
     CALL getin_p('rei_max',rei_max)
+    rei_coef = 2.4
+    CALL getin_p('rei_coef',rei_coef)
+    rei_min_temp = 175.
+    CALL getin_p('rei_min_temp',rei_min_temp)