!> @file compute_vpt.f90
!------------------------------------------------------------------------------!
! This file is part of the PALM model system.
!
! 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 1997-2020 Leibniz Universitaet Hannover
!------------------------------------------------------------------------------!
!
! Current revisions:
! -----------------
! 
! 
! Former revisions:
! -----------------
! $Id: compute_vpt.f90 4502 2020-04-17 16:14:16Z schwenkel $
! Implementation of ice microphysics
! 
! 4360 2020-01-07 11:25:50Z suehring
! Corrected "Former revisions" section
! 
! 3655 2019-01-07 16:51:22Z knoop
! Modularization of all bulk cloud physics code components
!
! Revision 1.1  2000/04/13 14:40:53  schroeter
! Initial revision
!
!
! Description:
! -------------
!> Computation of the virtual potential temperature 
!------------------------------------------------------------------------------!
 SUBROUTINE compute_vpt
 

    USE arrays_3d,                                                             &
        ONLY:  pt, q, ql, vpt, d_exner, qi

    USE basic_constants_and_equations_mod,                                     &
        ONLY:  lv_d_cp, ls_d_cp

    USE control_parameters,                                                    &
        ONLY:  cloud_droplets

    USE indices,                                                               &
        ONLY:  nzb, nzt

    USE kinds

    USE bulk_cloud_model_mod,                                                  &
        ONLY:  bulk_cloud_model, microphysics_ice_extension

    IMPLICIT NONE

    INTEGER(iwp) :: k   !< 

    IF ( .NOT. bulk_cloud_model  .AND.  .NOT. cloud_droplets )  THEN
       vpt = pt * ( 1.0_wp + 0.61_wp * q )
    ELSEIF ( bulk_cloud_model  .AND.  .NOT. microphysics_ice_extension )  THEN
       DO  k = nzb, nzt+1
              vpt(k,:,:) = ( pt(k,:,:) + d_exner(k) * lv_d_cp * ql(k,:,:) ) *  &
                       ( 1.0_wp + 0.61_wp * q(k,:,:) - 1.61_wp *  ql(k,:,:)  )
       ENDDO
    ELSEIF ( bulk_cloud_model  .AND.  microphysics_ice_extension ) THEN
       DO  k = nzb, nzt+1
          vpt(k,:,:) = ( pt(k,:,:) + d_exner(k) * lv_d_cp * ql(k,:,:)   +      &
                                     d_exner(k) * ls_d_cp * qi(k,:,:) ) *      &
                       ( 1.0_wp + 0.61_wp * q(k,:,:) - 1.61_wp          *      &
                                           ( ql(k,:,:) + qi(k,:,:) ) )
       ENDDO
    ELSE
       vpt = pt * ( 1.0_wp + 0.61_wp * q - ql ) 
    ENDIF

 END SUBROUTINE compute_vpt