Changeset 2608 for palm/trunk/SOURCE/land_surface_model_mod.f90

Timestamp:

Nov 13, 2017 2:04:26 PM (7 years ago)

Author:

schwenkel

Message:

Inital revision of diagnostic_quantities_mod allows unified calculation of magnus equation and saturion mixing ratio

File:

• palm/trunk/SOURCE/land_surface_model_mod.f90 (modified) (8 diffs)

palm/trunk/SOURCE/land_surface_model_mod.f90

@@ -25 +25 @@
 ! -----------------
 ! $Id$
+! Calculation of magnus equation in external module (diagnostic_quantities_mod).
+! Adjust calculation of vapor pressure and saturation mixing ratio that it is
+! consistent with formulations in other parts of PALM.
+! 
+! 2575 2017-10-24 09:57:58Z maronga
 ! Pavement parameterization revised
 ! 
@@ -1410 +1415 @@
  SUBROUTINE lsm_energy_balance( horizontal, l )
 
- 
+    USE diagnostic_quantities_mod,                                             &
+        ONLY:  magnus 
+
     USE pegrid
 
@@ -1648 +1655 @@
           f2 = 1.0E-20_wp
        ENDIF
-!
-!--    Calculate water vapour pressure at saturation 
-       e_s = 0.01_wp * 610.78_wp * EXP( 17.269_wp * ( surf_t_surface%var_1d(m) &
-                     - 273.16_wp ) / ( surf_t_surface%var_1d(m) - 35.86_wp ) )
+
+!
+!--    Calculate water vapour pressure at saturation and convert to hPa
+       e_s = 0.01_wp * magnus( surf_t_surface%var_1d(m) )
+
 !
 !--    f3: correction for vapour pressure deficit
@@ -1657 +1665 @@
 !
 !--       Calculate vapour pressure
-          e  = qv1 * surface_pressure / 0.622_wp
+          e  = qv1 * surface_pressure / ( qv1 + 0.622_wp )
           f3 = EXP ( - surf%g_d(m) * (e_s - e) )
        ELSE
@@ -1698 +1706 @@
 !
 !--    Calculate saturation specific humidity
-       q_s = 0.622_wp * e_s / surface_pressure
+       q_s = 0.622_wp * e_s / ( surface_pressure - e_s )
 !
 !--    In case of dewfall, set evapotranspiration to zero
@@ -1733 +1741 @@
 !
 !--    Calculate derivative of q_s for Taylor series expansion
-       e_s_dt = e_s * ( 17.269_wp / ( surf_t_surface%var_1d(m) - 35.86_wp) -   &
-                        17.269_wp*( surf_t_surface%var_1d(m) - 273.16_wp)      &
-                       / ( surf_t_surface%var_1d(m) - 35.86_wp)**2 )
-
-       dq_s_dt = 0.622_wp * e_s_dt / surface_pressure
+       e_s_dt = e_s * ( 17.62_wp / ( surf_t_surface%var_1d(m) - 29.65_wp) -   &
+                        17.62_wp*( surf_t_surface%var_1d(m) - 273.15_wp)      &
+                       / ( surf_t_surface%var_1d(m) - 29.65_wp)**2 )
+
+       dq_s_dt = 0.622_wp * e_s_dt / ( surface_pressure - e_s_dt )
 !
 !--    Add LW up so that it can be removed in prognostic equation
@@ -1988 +1996 @@
     SUBROUTINE calc_q_surface
 
+       USE diagnostic_quantities_mod
+
        IMPLICIT NONE
 
@@ -1997 +2007 @@
           j   = surf%j(m)
           k   = surf%k(m)
-
-!
-!--       Calculate water vapour pressure at saturation
-          e_s = 0.01_wp * 610.78_wp * EXP( 17.269_wp *                         &
-                                 ( surf_t_surface_p%var_1d(m) - 273.16_wp ) /  &
-                                 ( surf_t_surface_p%var_1d(m) - 35.86_wp  )    &
-                                         )
+!
+!--       Calculate water vapour pressure at saturation and convert to hPa
+          e_s = 0.01_wp * magnus( surf_t_surface_p%var_1d(m) )                   
 
 !
 !--       Calculate specific humidity at saturation
-          q_s = 0.622_wp * e_s / surface_pressure 
+          q_s = 0.622_wp * e_s / ( surface_pressure - e_s )
 
           resistance = surf%r_a(m) / ( surf%r_a(m) + surf%r_s(m) )