MODULE calc_precipitation_mod

!--------------------------------------------------------------------------------!
! This file is part of PALM.
!
! PALM is free software: you can redistribute it and/or modify it under the terms
! of the GNU General Public License as published by the Free Software Foundation,
! either version 3 of the License, or (at your option) any later version.
!
! PALM is distributed in the hope that it will be useful, but WITHOUT ANY
! WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
! A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
!
! You should have received a copy of the GNU General Public License along with
! PALM. If not, see <http://www.gnu.org/licenses/>.
!
! Copyright 1997-2014 Leibniz Universitaet Hannover
!--------------------------------------------------------------------------------!
!
! Current revisions:
! -----------------
!
!
! Former revisions:
! -----------------
! $Id: calc_precipitation.f90 1321 2014-03-20 09:40:40Z kanani $
!
! 1320 2014-03-20 08:40:49Z raasch
! ONLY-attribute added to USE-statements,
! kind-parameters added to all INTEGER and REAL declaration statements,
! kinds are defined in new module kinds,
! revision history before 2012 removed,
! comment fields (!:) to be used for variable explanations added to
! all variable declaration statements
!
! 1036 2012-10-22 13:43:42Z raasch
! code put under GPL (PALM 3.9)
!
! Revision 1.1  2000/04/13 14:45:22  schroeter
! Initial revision
!
!
!
! Description:
! ------------
! Calculate the change of total water content due to precipitation
! (simplified Kessler scheme)
!------------------------------------------------------------------------------!

    PRIVATE
    PUBLIC calc_precipitation

    INTERFACE calc_precipitation
       MODULE PROCEDURE calc_precipitation
       MODULE PROCEDURE calc_precipitation_ij
    END INTERFACE calc_precipitation

 CONTAINS


!------------------------------------------------------------------------------!
! Call for all grid points
!------------------------------------------------------------------------------!
    SUBROUTINE calc_precipitation

       USE arrays_3d,                                                          &
           ONLY:  dzw, ql, tend

       USE cloud_parameters,                                                   &
           ONLY:  precipitation_amount, precipitation_rate, prec_time_const,   &
                  ql_crit

       USE control_parameters,                                                 &
           ONLY:  dt_do2d_xy, dt_3d,                                           &
                  intermediate_timestep_count, intermediate_timestep_count_max,&
                  precipitation_amount_interval, time_do2d_xy

       USE indices,                                                            &
           ONLY:  nxl, nxr, nyn, nys, nzb_2d, nzt

       USE kinds


       IMPLICIT NONE

       INTEGER(iwp) ::  i !:
       INTEGER(iwp) ::  j !:
       INTEGER(iwp) ::  k !:
       
       REAL(wp)    ::  dqdt_precip !:

       precipitation_rate = 0.0

       DO  i = nxl, nxr
          DO  j = nys, nyn
             DO  k = nzb_2d(j,i)+1, nzt

                IF ( ql(k,j,i) > ql_crit )  THEN
                   dqdt_precip = prec_time_const * ( ql(k,j,i) - ql_crit )
                ELSE
                   dqdt_precip = 0.0
                ENDIF
                tend(k,j,i) = tend(k,j,i) - dqdt_precip
!
!--             Precipitation rate in kg / m**2 / s (= mm/s)
                precipitation_rate(j,i) = precipitation_rate(j,i) +            &
                                          dqdt_precip * dzw(k)

             ENDDO
!
!--          Sum up the precipitation amount, unit kg / m**2 (= mm)
             IF ( intermediate_timestep_count ==                               &
                  intermediate_timestep_count_max  .AND.                       &
                  ( dt_do2d_xy-time_do2d_xy ) < precipitation_amount_interval )&
             THEN
                precipitation_amount(j,i) = precipitation_amount(j,i) +        &
                                            precipitation_rate(j,i) * dt_3d
             ENDIF
          ENDDO
       ENDDO

    END SUBROUTINE calc_precipitation


!------------------------------------------------------------------------------!
! Call for grid point i,j
!------------------------------------------------------------------------------!
    SUBROUTINE calc_precipitation_ij( i, j )

       USE arrays_3d,                                                          &
           ONLY:  dzw, ql, tend

       USE cloud_parameters,                                                   &
           ONLY:  precipitation_amount, precipitation_rate, prec_time_const,   &
                  ql_crit

       USE control_parameters,                                                 &
           ONLY:  dt_do2d_xy, dt_3d,                                           &
                  intermediate_timestep_count, intermediate_timestep_count_max,&
                  precipitation_amount_interval, time_do2d_xy

       USE indices,                                                            &
           ONLY:  nzb_2d, nzt

       USE kinds


       IMPLICIT NONE

       INTEGER(iwp) ::  i !:
       INTEGER(iwp) ::  j !:
       INTEGER(iwp) ::  k !:
       
       REAL(wp)    ::  dqdt_precip !:       

       precipitation_rate(j,i) = 0.0

!
!--    Ghostpoints are included (although not needed for tend) to avoid a later
!--    exchange of these data for the precipitation amount/rate arrays
       DO  k = nzb_2d(j,i)+1, nzt

          IF ( ql(k,j,i) > ql_crit )  THEN
             dqdt_precip = prec_time_const * ( ql(k,j,i) - ql_crit )
          ELSE
             dqdt_precip = 0.0
          ENDIF
          tend(k,j,i) = tend(k,j,i) - dqdt_precip

!
!--       Precipitation rate in kg / m**2 / s (= mm/s)
          precipitation_rate(j,i) = precipitation_rate(j,i) + dqdt_precip *    &
                                                              dzw(k)

       ENDDO

!
!--    Sum up the precipitation amount , unit kg / m**2 (= mm)
       IF ( intermediate_timestep_count == intermediate_timestep_count_max     &
            .AND. ( dt_do2d_xy-time_do2d_xy ) < precipitation_amount_interval )&
       THEN
          precipitation_amount(j,i) = precipitation_amount(j,i) +              &
                                      precipitation_rate(j,i) * dt_3d
       ENDIF

    END SUBROUTINE calc_precipitation_ij

 END MODULE calc_precipitation_mod