Changeset 3157 for palm/trunk/SOURCE/surface_layer_fluxes_mod.f90

Timestamp:

Jul 19, 2018 9:08:49 PM (7 years ago)

Author:

maronga

Message:

added local free convection velocity scale in calculation of horizontal wind at first grid level

File:

• palm/trunk/SOURCE/surface_layer_fluxes_mod.f90 (modified) (6 diffs)

palm/trunk/SOURCE/surface_layer_fluxes_mod.f90

@@ -26 +26 @@
 ! -----------------
 ! $Id$
+! Added local free convection velocity scale w_lfc in calculation of uvw_abs.
+! This can be switche on/off by the user via the flag namelist parameter 
+! use_free_convection_scaling
+! 
+! 3152 2018-07-19 13:26:52Z suehring
 ! q_surface is now part of surface structure
 ! 
@@ -246 +251 @@
                most_method, neutral, passive_scalar, pt_surface, q_surface,    &
                run_coupled, surface_pressure, simulated_time, terminate_run,   &
-               time_since_reference_point, urban_surface, zeta_max, zeta_min
+               time_since_reference_point, urban_surface,                      &
+               use_free_convection_scaling, zeta_max, zeta_min
 
     USE grid_variables,                                                        &
@@ -952 +958 @@
 !------------------------------------------------------------------------------!
     SUBROUTINE calc_uvw_abs
-
+    
        IMPLICIT NONE
 
@@ -961 +967 @@
        INTEGER(iwp) ::  m             !< running index surface elements
 
+       REAL(wp)     :: w_lfc          !< local free convection velocity scale
 !
 !--    ibit is 1 for upward-facing surfaces, zero for downward-facing surfaces.
@@ -970 +977 @@
           j   = surf%j(m)
           k   = surf%k(m)
+       
+!
+!--       Calculate free convection velocity scale w_lfc is 
+!--       use_free_convection_scaling = .T.. This will maintain a horizontal
+!--       velocity even for very weak wind convective conditions. SIGN is used
+!--       to set w_lfc to zero under stable conditions.
+          IF ( use_free_convection_scaling )  THEN 
+             w_lfc = ABS(g / surf%pt1(m) * surf%z_mo(m) * surf%shf(m))
+             w_lfc = ( 0.5_wp * ( w_lfc + SIGN(w_lfc,surf%shf(m)) ) )**(0.33333_wp)
+          ELSE
+             w_lfc = 0.0_wp
+          ENDIF
+
 !
 !--       Compute the absolute value of the horizontal velocity.
@@ -991 +1011 @@
                                            ) * ibit                            &
                                          )                                     &
-                              )**2                                             &
+                              )**2  + w_lfc**2                                 &
                                 )