The external pressure-gradient

INTERFACE:

   subroutine extpressure(method,nlev)

DESCRIPTION:

This subroutine calculates the external pressure-gradient. Two methods are implemented here, relating either to the velocity vector at a given height above bed prescribed or to the vector for the vertical mean velocity. In the first case, dpdx and dpdy are $x$- and $y$-components of the prescribed velocity vector at the height h_press above the bed. The velocity profile will in this routive be shifted by a vertically constant vector such that the resulting profile has an (interpolated) velocity at h_press which is identical to the prescribed value. In the second case, dpdx and dpdy are $x$- and $y$-components of the prescribed vertical mean velocity vector, and h_press is not used. Here the velocity profile is shifted in such a way that the resulting mean velocty vector is identical to dpdx and dpdy.

For both cases, this is a recalculation of the external pressure gradient, since at all points the same acceleration has been applied in this operator split method.

If the external pressure-gradient is prescribed by the surface slope, then it is directly inserted in (12) and (14).

For details of this method, see Burchard (1999).

USES:

   use meanflow,     only: u,v,h
   use observations, only: dpdx,dpdy,h_press
   IMPLICIT NONE

INPUT PARAMETERS:

 
   method to compute external
   pressure gradient
   integer, intent(in)                 :: method
 
   number of vertical layers
   integer, intent(in)                 :: nlev

REVISION HISTORY:

   Original author(s): Hans Burchard & Karsten Bolding
   $Log: extpressure.F90,v $
   Revision 1.9  2007-01-06 11:57:08  kbk
   PressMethod --> ext_press_mode
   Revision 1.8  2007-01-06 11:49:15  kbk
   namelist file extension changed .inp --> .nml
   Revision 1.7  2006-12-07 16:50:28  hb
   Program abortion introduced for PressHeight<=0 when ext_press_mode=1
   Revision 1.6  2005-06-27 13:44:07  kbk
   modified + removed traling blanks
   Revision 1.5  2004/08/18 11:41:02  lars
   corrected typo in docu
   Revision 1.4  2003/03/28 09:20:35  kbk
   added new copyright to files
   Revision 1.3  2003/03/28 08:56:56  kbk
   removed tabs
   Revision 1.2  2003/03/10 08:50:06  gotm
   Improved documentation and cleaned up code
   Revision 1.1.1.1  2001/02/12 15:55:57  gotm
   initial import into CVS