From 41527dd33221e10952f9de0fdc30dcc22d4926c0 Mon Sep 17 00:00:00 2001
From: Ufuk Turuncoglu <turuncu@ucar.edu>
Date: Thu, 7 Nov 2024 22:59:45 -0600
Subject: [PATCH] skip land component for first time step

---
 physics/SFC_Models/Land/Noahmp/noahmpdrv.F90  | 6 ++++--
 physics/SFC_Models/Land/Noahmp/noahmpdrv.meta | 7 +++++++
 physics/SFC_Models/Land/sfc_land.F90          | 7 ++++---
 physics/SFC_Models/Land/sfc_land.meta         | 7 +++++++
 4 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/physics/SFC_Models/Land/Noahmp/noahmpdrv.F90 b/physics/SFC_Models/Land/Noahmp/noahmpdrv.F90
index 1313e9ff3..56b2706b8 100644
--- a/physics/SFC_Models/Land/Noahmp/noahmpdrv.F90
+++ b/physics/SFC_Models/Land/Noahmp/noahmpdrv.F90
@@ -127,7 +127,8 @@ end subroutine noahmpdrv_init
   subroutine noahmpdrv_run                                       &
 !...................................
 !  ---  inputs:
-    ( im, km, lsnowl, itime, ps, u1, v1, t1, q1, soiltyp,soilcol,&
+    ( im, km, lsnowl, itime, flag_init, ps, u1, v1, t1, q1,      &
+      soiltyp,soilcol,                                           &
       vegtype, sigmaf, dlwflx, dswsfc, snet, delt, tg3, cm, ch,  &
       prsl1, prslk1, prslki, prsik1, zf,pblh, dry, wind, slopetyp,&
       shdmin, shdmax, snoalb, sfalb, flag_iter,con_g,            &
@@ -233,6 +234,7 @@ subroutine noahmpdrv_run                                       &
   integer                                , intent(in)    :: km         ! vertical soil layer dimension
   integer                                , intent(in)    :: lsnowl     ! lower bound for snow level arrays
   integer                                , intent(in)    :: itime      ! NOT USED
+  logical                                , intent(in)    :: flag_init  ! flag signaling first time step
   real(kind=kind_phys), dimension(:)     , intent(in)    :: ps         ! surface pressure [Pa]
   real(kind=kind_phys), dimension(:)     , intent(in)    :: u1         ! u-component of wind [m/s]
   real(kind=kind_phys), dimension(:)     , intent(in)    :: v1         ! u-component of wind [m/s]
@@ -693,7 +695,7 @@ subroutine noahmpdrv_run                                       &
 !
 !  --- Just return if external land component is activated for two-way interaction
 !
-  if (cpllnd .and. cpllnd2atm) return
+  if (cpllnd .and. cpllnd2atm .and. (.not. flag_init)) return
 
   do i = 1, im
 
diff --git a/physics/SFC_Models/Land/Noahmp/noahmpdrv.meta b/physics/SFC_Models/Land/Noahmp/noahmpdrv.meta
index 753550016..75bd4d7e1 100644
--- a/physics/SFC_Models/Land/Noahmp/noahmpdrv.meta
+++ b/physics/SFC_Models/Land/Noahmp/noahmpdrv.meta
@@ -129,6 +129,13 @@
   dimensions = ()
   type = integer
   intent = in
+[flag_init]
+  standard_name = flag_for_first_timestep
+  long_name = flag signaling first time step for time integration loop
+  units = flag
+  dimensions = ()
+  type = logical
+  intent = in
 [ps]
   standard_name = surface_air_pressure
   long_name = surface pressure
diff --git a/physics/SFC_Models/Land/sfc_land.F90 b/physics/SFC_Models/Land/sfc_land.F90
index a85e8b787..36bdcdc09 100644
--- a/physics/SFC_Models/Land/sfc_land.F90
+++ b/physics/SFC_Models/Land/sfc_land.F90
@@ -28,8 +28,8 @@ module sfc_land
 !! \section general General Algorithm
 !! \section detailed Detailed Algorithm
 !! @{
-   subroutine sfc_land_run(im, cpllnd, cpllnd2atm, flag_iter, dry,   &
-     sncovr1_lnd, qsurf_lnd, evap_lnd, hflx_lnd,                     &
+   subroutine sfc_land_run(im, flag_init, cpllnd, cpllnd2atm,        &
+     flag_iter, dry, sncovr1_lnd, qsurf_lnd, evap_lnd, hflx_lnd,     &
      ep_lnd, t2mmp_lnd, q2mp_lnd, gflux_lnd,                         &
      runoff_lnd, drain_lnd, cmm_lnd, chh_lnd, zvfun_lnd,             &
      sncovr1, qsurf, evap, hflx, ep, t2mmp, q2mp,                    &
@@ -40,6 +40,7 @@ subroutine sfc_land_run(im, cpllnd, cpllnd2atm, flag_iter, dry,   &
 
    ! Inputs
    integer             , intent(in)    :: im
+   logical             , intent(in)    :: flag_init
    logical             , intent(in)    :: cpllnd
    logical             , intent(in)    :: cpllnd2atm
    logical             , intent(in)    :: flag_iter(:)
@@ -83,7 +84,7 @@ subroutine sfc_land_run(im, cpllnd, cpllnd2atm, flag_iter, dry,   &
    errflg = 0
 
    ! Check coupling from component land to atmosphere
-   if (.not. cpllnd2atm) return
+   if (flag_init .or. (.not. cpllnd2atm)) return
 
    ! Fill variables
    do i = 1, im
diff --git a/physics/SFC_Models/Land/sfc_land.meta b/physics/SFC_Models/Land/sfc_land.meta
index 15790145e..84c4ccdce 100644
--- a/physics/SFC_Models/Land/sfc_land.meta
+++ b/physics/SFC_Models/Land/sfc_land.meta
@@ -14,6 +14,13 @@
   dimensions = ()
   type = integer
   intent = in
+[flag_init]
+  standard_name = flag_for_first_timestep
+  long_name = flag signaling first time step for time integration loop
+  units = flag
+  dimensions = ()
+  type = logical
+  intent = in
 [cpllnd]
   standard_name = flag_for_land_coupling
   long_name = flag controlling cpllnd collection (default off)