# source:trunk/src/psim.f90@28

Last change on this file since 28 was 4, checked in by mlanger, 10 years ago
File size: 2.2 KB
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[4]1!**********************************************************************
2! Copyright 1998,1999,2000,2001,2002,2005,2007,2008,2009,2010         *
3! Andreas Stohl, Petra Seibert, A. Frank, Gerhard Wotawa,             *
4! Caroline Forster, Sabine Eckhardt, John Burkhart, Harald Sodemann   *
5!                                                                     *
6! This file is part of FLEXPART.                                      *
7!                                                                     *
8! FLEXPART is free software: you can redistribute it and/or modify    *
9! it under the terms of the GNU General Public License as published by*
10! the Free Software Foundation, either version 3 of the License, or   *
11! (at your option) any later version.                                 *
12!                                                                     *
13! FLEXPART is distributed in the hope that it will be useful,         *
14! but WITHOUT ANY WARRANTY; without even the implied warranty of      *
15! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the       *
16! GNU General Public License for more details.                        *
17!                                                                     *
18! You should have received a copy of the GNU General Public License   *
19! along with FLEXPART.  If not, see <http://www.gnu.org/licenses/>.   *
20!**********************************************************************
21
22real function psim(z,al)
23
24  !**********************************************************************
25  !                                                                     *
26  ! DESCRIPTION: CALCULATION OF THE STABILITY CORRECTION FUNCTION FOR   *
27  !              MOMENTUM AS FUNCTION OF HEIGHT Z AND OBUKHOV SCALE     *
28  !              HEIGHT L                                               *
29  !                                                                     *
30  !**********************************************************************
31
32  use par_mod
33
34  implicit none
35
36  real :: z,al,zeta,x,a1,a2
37
38  zeta=z/al
39  if(zeta.le.0.) then
40  ! UNSTABLE CASE
41    x=(1.-15.*zeta)**0.25
42    a1=((1.+x)/2.)**2
43    a2=(1.+x**2)/2.
44    psim=log(a1*a2)-2.*atan(x)+pi/2.
45  else
46  ! STABLE CASE
47    psim=-4.7*zeta
48  endif
49
50end function psim
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