Fix dimensional scaling and use Adcroft reciprocal

* mle_fl_2d is [L ~> m]; added scale=US%m_to_L in the
time_interp_external call;

* Use Adcroft reciprocal to compute I_LFront.

src/parameterizations/lateral/MOM_mixed_layer_restrat.F90

@@ -220,7 +220,7 @@ subroutine mixedlayer_restrat_OM4(h, uhtr, vhtr, tv, forces, dt, h_MLD, VarMix,
     Rml_av_fast, &        ! Negative g_Rho0 times the average mixed layer density or G_Earth
                           ! times the average specific volume [L2 H-1 T-2 ~> m s-2 or m4 kg-1 s-2]
     MLD_slow,  &          ! Mixed layer depth actually used in MLE restratification parameterization [H ~> m or kg m-2]
-    mle_fl_2d, &          ! MLE frontal length-scale                                [H ~> m or kg m-2]
+    mle_fl_2d, &          ! MLE frontal length-scale                                [L ~> m]
     htot_slow, &          ! The sum of the thicknesses of layers in the mixed layer [H ~> m or kg m-2]
     Rml_av_slow           ! Negative g_Rho0 times the average mixed layer density or G_Earth
                           ! times the average specific volume [L2 H-1 T-2 ~> m s-2 or m4 kg-1 s-2]
@@ -359,7 +359,7 @@ subroutine mixedlayer_restrat_OM4(h, uhtr, vhtr, tv, forces, dt, h_MLD, VarMix,
     enddo ; enddo
   elseif (CS%front_length == 0. .and. CS%fl_from_file) then
     res_upscale = .true.
-    call time_interp_external(CS%sbc_fl, CS%Time, mle_fl_2d, turns=G%HI%turns)
+    call time_interp_external(CS%sbc_fl, CS%Time, mle_fl_2d, turns=G%HI%turns, scale=US%m_to_L)
     call pass_var(mle_fl_2d, G%domain, halo=1)
     do j=js,je ; do i=is,ie
       if ((G%mask2dT(i,j) > 0.0) .and. (mle_fl_2d(i,j) < 0.0)) then
@@ -490,11 +490,8 @@ subroutine mixedlayer_restrat_OM4(h, uhtr, vhtr, tv, forces, dt, h_MLD, VarMix,
     absf = 0.5*(abs(G%CoriolisBu(I,J-1)) + abs(G%CoriolisBu(I,J)))
     ! Compute I_LFront = 1 / (frontal length scale) [m-1]
     lfront = 0.5 * (mle_fl_2d(i,j) + mle_fl_2d(i+1,j))
-    if (lfront > 0.) then
-      I_LFront = 1./lfront
-    else
-      I_LFront = 0.0
-    endif
+    ! Adcroft reciprocal
+    I_LFront = 0.0 ; if (lfront /= 0.0) I_LFront = 1.0/lfront
     ! If needed, res_scaling_fac = min( ds, L_d ) / l_f
     if (res_upscale) res_scaling_fac = &
           ( sqrt( 0.5 * ( (G%dxCu(I,j)**2) + (G%dyCu(I,j)**2) ) ) * I_LFront ) &
@@ -582,11 +579,8 @@ subroutine mixedlayer_restrat_OM4(h, uhtr, vhtr, tv, forces, dt, h_MLD, VarMix,
     u_star = max(CS%ustar_min, 0.5*(U_star_2d(i,j) + U_star_2d(i,j+1)))
     ! Compute I_LFront = 1 / (frontal length scale) [m-1]
     lfront = 0.5 * (mle_fl_2d(i,j) + mle_fl_2d(i,j+1))
-    if (lfront > 0.) then
-      I_LFront = 1./lfront
-    else
-      I_LFront = 0.0
-    endif
+    ! Adcroft reciprocal
+    I_LFront = 0.0 ; if (lfront /= 0.0) I_LFront = 1.0/lfront
     absf = 0.5*(abs(G%CoriolisBu(I-1,J)) + abs(G%CoriolisBu(I,J)))
     ! If needed, res_scaling_fac = min( ds, L_d ) / l_f
     if (res_upscale) res_scaling_fac = &
@@ -1646,7 +1640,7 @@ logical function mixedlayer_restrat_init(Time, G, GV, US, param_file, diag, CS,
 
 # include "version_variable.h"
   integer :: i, j
-  character(len=200) :: filename, inputdir, varname
+  character(len=200) :: filename, varname
 
   ! Read all relevant parameters and write them to the model log.
   call get_param(param_file, mdl, "MIXEDLAYER_RESTRAT", mixedlayer_restrat_init, &