!################################################################## 
!################################################################## 
!######                                                      ######
!######                    MODULE BNDRY                      ######
!######                                                      ######
!######                     Developed by                     ######
!######     Center for Analysis and Prediction of Storms     ######
!######                University of Oklahoma                ######
!######                                                      ######
!##################################################################
!##################################################################

MODULE BNDRY

!----------------------------------------------------------------------- 
! PURPOSE: 
!
! Declare boundary condition control parameters for the east, west, 
! north, south, top and bottom boundaries. 
!-----------------------------------------------------------------------
! AUTHOR: Ming Xue
! 10/01/1991
!
! MODIFICATION HISTORY:
!
! 7/25/92 (MX)
! Added parameter rbcopt
!
! 7/29/97.  Dan Weber
! Added fftopt for distingushing the type of FFT used in the upper
! radiation condition.
!-----------------------------------------------------------------------

  IMPLICIT NONE 
  SAVE 
 
  INTEGER :: lbcopt ! Lateral boundary condition option;
                    ! = 1, for internal determined LBC
                    ! = 2, for externally forced LBC

!-----------------------------------------------------------------------
! The boundary conditions are defined independent of each
! boundary, but should be consistent. 
!
! When the value of the above parameters is:
! = 1, rigid wall boundary condition 
! = 2, periodic boundary condition 
! = 3, zero gradient boundary condition (specified for all variables) 
! = 4, radiation (open) boundary condition 
! = 5, user specified boundary conditon (externally) 
!-----------------------------------------------------------------------

  INTEGER :: ebc    ! east   boundary condition option.
  INTEGER :: wbc    ! west   boundary condition option.
  INTEGER :: nbc    ! north  boundary condition option.
  INTEGER :: sbc    ! south  boundary condition option.
  INTEGER :: tbc    ! top    boundary condition option.
  INTEGER :: bbc    ! bottom boundary condition option.

  INTEGER :: fftopt ! FFT option for tbc=4 configuration.

  INTEGER :: rbcopt ! Radiation lateral boundary condition option:
                    ! = 1, Klemp & Wihelmson type with constant phase speed c = c_phase
                    ! = 2, Orlanski type, with estimated phase speed c

  INTEGER :: pdetrnd   ! Option for detrending pressure

  REAL :: c_phase   ! Fixed phase speed of waves propagating out of 
                    ! lateral boundary. Used by option rbcopt=1. 

  REAL :: rlxlbc    ! Inflow boundary relaxation coefficient.

END MODULE bndry