+Add runtime parameter KPP_LT_MLD_GUESS_MIN

  Added the new runtime parameter KPP_LT_MLD_GUESS_MIN to specify a previously
hard-coded lower limit on the estimate of the boundary layer depth used to
calculate the Langmuir number for some options with KPP.  By default all answers
are bitwise identical, but there is a new entry in the MOM_parameter_doc.all
files for some configurations with a KPP and Langmuir enhanced turbulence.

src/parameterizations/vertical/MOM_CVMix_KPP.F90

@@ -113,6 +113,9 @@ module MOM_CVMix_KPP
   logical :: LT_Vt2_Enhancement        !< Flags if enhancing Vt2 due to LT
   integer :: LT_VT2_METHOD             !< Integer for Vt2 LT method
   real    :: KPP_VT2_ENH_FAC           !< Factor to multiply by VT2 if Method is CONSTANT [nondim]
+  real    :: MLD_guess_min             !< The minimum estimate of the mixed layer depth used to
+                                       !! calculate the Langmuir number for Langmuir turbulence
+                                       !! enhancement with KPP [Z ~> m]
   logical :: STOKES_MIXING             !< Flag if model is mixing down Stokes gradient
                                        !! This is relevant for which current to use in RiB
 
@@ -460,6 +463,13 @@ logical function KPP_init(paramFile, G, GV, US, diag, Time, CS, passive)
     endif
   endif
 
+  if (CS%LT_K_ENHANCEMENT .or. CS%LT_VT2_ENHANCEMENT) then
+    call get_param(paramFile, mdl, "KPP_LT_MLD_GUESS_MIN", CS%MLD_guess_min,     &
+                   "The minimum estimate of the mixed layer depth used to calculate "//&
+                   "the Langmuir number for Langmuir turbulence enhancement with KPP.", &
+                   units="m", default=1.0, scale=US%m_to_Z)
+  endif
+
   call closeParameterBlock(paramFile)
 
   call get_param(paramFile, mdl, 'DEBUG', CS%debug, default=.False., do_not_log=.True.)
@@ -658,10 +668,7 @@ subroutine KPP_calculate(CS, G, GV, US, h, uStar, buoyFlux, Kt, Ks, Kv, &
   !$OMP                           Ks, Kv, nonLocalTransHeat, nonLocalTransScalar, Waves, lamult)
   ! loop over horizontal points on processor
   do j = G%jsc, G%jec
-    do i = G%isc, G%iec
-
-      ! skip calling KPP for land points
-      if (G%mask2dT(i,j)==0.) cycle
+    do i = G%isc, G%iec ; if (G%mask2dT(i,j) > 0.0) then
 
       ! things independent of position within the column
       surfFricVel = US%Z_to_m*US%s_to_T * uStar(i,j)
@@ -869,7 +876,7 @@ subroutine KPP_calculate(CS, G, GV, US, h, uStar, buoyFlux, Kt, Ks, Kv, &
 
 
     ! end of the horizontal do-loops over the vertical columns
-    enddo ! i
+    endif ; enddo ! i
   enddo ! j
 
   call cpu_clock_end(id_clock_KPP_calc)
@@ -1000,10 +1007,7 @@ subroutine KPP_compute_BLD(CS, G, GV, US, h, Temp, Salt, u, v, tv, uStar, buoyFl
   !$OMP                           shared(G, GV, CS, US, uStar, h, buoy_scale, buoyFlux,     &
   !$OMP                           Temp, Salt, waves, tv, GoRho, GoRho_Z_L2, u, v, lamult)
   do j = G%jsc, G%jec
-    do i = G%isc, G%iec
-
-      ! skip calling KPP for land points
-      if (G%mask2dT(i,j)==0.) cycle
+    do i = G%isc, G%iec ; if (G%mask2dT(i,j) > 0.0) then
 
       do k=1,GV%ke
         U_H(k) = 0.5 * (u(i,j,k)+u(i-1,j,k))
@@ -1120,10 +1124,10 @@ subroutine KPP_compute_BLD(CS, G, GV, US, h, Temp, Salt, u, v, tv, uStar, buoyFl
       enddo ! k-loop finishes
 
       if ( (CS%LT_K_ENHANCEMENT .or. CS%LT_VT2_ENHANCEMENT) .and. .not. present(lamult)) then
-        MLD_guess = max( 1.*US%m_to_Z, abs(CS%OBLdepthprev(i,j) ) )
+        MLD_guess = max( CS%MLD_guess_min, abs(CS%OBLdepthprev(i,j) ) )
         call get_Langmuir_Number(LA, G, GV, US, MLD_guess, uStar(i,j), i, j, &
                                  H=H(i,j,:), U_H=U_H, V_H=V_H, WAVES=WAVES)
-        CS%La_SL(i,j)=LA
+        CS%La_SL(i,j) = LA
       endif
 
 
@@ -1265,7 +1269,7 @@ subroutine KPP_compute_BLD(CS, G, GV, US, h, Temp, Salt, u, v, tv, uStar, buoyFl
       if (CS%id_Usurf  > 0)   CS%Usurf(i,j)    = surfU
       if (CS%id_Vsurf  > 0)   CS%Vsurf(i,j)    = surfV
 
-    enddo
+    endif ; enddo
   enddo
 
   call cpu_clock_end(id_clock_KPP_compute_BLD)
@@ -1326,10 +1330,7 @@ subroutine KPP_smooth_BLD(CS, G, GV, US, h)
     !$OMP parallel do default(none) shared(G, GV, US, CS, h, OBLdepth_prev) &
     !$OMP                           private(wc, ww, we, wn, ws, dh, hcorr, cellHeight, iFaceHeight)
     do j = G%jsc, G%jec
-      do i = G%isc, G%iec
-
-         ! skip land points
-        if (G%mask2dT(i,j)==0.) cycle
+      do i = G%isc, G%iec ; if (G%mask2dT(i,j) > 0.0) then
 
         iFaceHeight(1) = 0.0 ! BBL is all relative to the surface
         hcorr = 0.
@@ -1363,7 +1364,7 @@ subroutine KPP_smooth_BLD(CS, G, GV, US, h)
         ! prevent OBL depths deeper than the bathymetric depth
         CS%OBLdepth(i,j) = min( CS%OBLdepth(i,j), -iFaceHeight(GV%ke+1) ) ! no deeper than bottom
         CS%kOBL(i,j)     = CVMix_kpp_compute_kOBL_depth( iFaceHeight, cellHeight, CS%OBLdepth(i,j) )
-      enddo
+      endif ; enddo
     enddo
 
   enddo ! s-loop