!> @file user_flight.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 1997-2019 Leibniz Universitaet Hannover
!------------------------------------------------------------------------------!
!
! Current revisions:
! ------------------
! 
! 
! Former revisions:
! -----------------
! $Id: user_flight.f90 4182 2019-08-22 15:20:23Z resler $
! Corrected "Former revisions" section
! 
! 3768 2019-02-27 14:35:58Z raasch
! unused variables commented out + statement added to avoid compiler warnings
! 
! 3684 2019-01-20 20:20:58Z knoop
! Corrected "Former revisions" section
! 
! 1957 2016-07-07 10:43:48Z suehring
! Initial revision
!
! Description:
! ------------
!> Calculation of user-defined output quantity for flight measurements after 
!> each timestep. 
!------------------------------------------------------------------------------!
 SUBROUTINE user_flight( var, id )

    USE control_parameters
    
    USE grid_variables

    USE indices

    USE kinds

    USE user

    USE arrays_3d

    IMPLICIT NONE

!    INTEGER(iwp) ::  i  !< index along x
!    INTEGER(iwp) ::  j  !< index along y
!    INTEGER(iwp) ::  k  !< index along z
    INTEGER(iwp) ::  id !< variable identifyer, according to the settings in user_init_flight
        
    REAL(wp), DIMENSION(nzb:nzt+1,nysg:nyng,nxlg:nxrg) ::  var !< treated variable

!
!-- Next line is to avoid compiler warning about unused variables. Please remove.
    IF ( id == 0  .OR.  var(nzb,nysg,nxlg) == 0.0_wp )  CONTINUE

!
!-- Here, the respective variable is calculated. There is no call of 
!-- exchange_horiz necessary. 
!-- The variable identifyer (id) must be set according to the settings in 
!-- user_init_flight.
!-- Please note, so far, variable must be located at the center of a grid box.
!     var = 0.0_wp

!     SELECT CASE ( id )
! 
!        CASE ( 1 )
!           DO i = nxl-1, nxr+1
!              DO j = nys-1, nyn+1
!                 DO k = nzb, nzt
!                    var(k,j,i) = ABS( u(k,j,i )
!                 ENDDO
!              ENDDO
!           ENDDO
!           
!        CASE ( 2 )
!           DO i = nxl-1, nxr+1
!              DO j = nys-1, nyn+1
!                 DO k = nzb, nzt
!                    var(k,j,i) = ABS( v(k,j,i) )
!                 ENDDO
!              ENDDO
!           ENDDO
! 
!     END SELECT


 END SUBROUTINE user_flight