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!**********************************************************************
! Copyright 1998,1999,2000,2001,2002,2005,2007,2008,2009,2010 *
! Andreas Stohl, Petra Seibert, A. Frank, Gerhard Wotawa, *
! Caroline Forster, Sabine Eckhardt, John Burkhart, Harald Sodemann *
! *
! This file is part of FLEXPART. *
! *
! FLEXPART 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. *
! *
! FLEXPART 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 FLEXPART. If not, see <http://www.gnu.org/licenses/>. *
!**********************************************************************
subroutine initialize(itime,ldt,up,vp,wp, &
usigold,vsigold,wsigold,xt,yt,zt,icbt)
! i i o o o
! o o o i i i o
!*****************************************************************************
! *
! Calculation of trajectories utilizing a zero-acceleration scheme. The time*
! step is determined by the Courant-Friedrichs-Lewy (CFL) criterion. This *
! means that the time step must be so small that the displacement within *
! this time step is smaller than 1 grid distance. Additionally, a temporal *
! CFL criterion is introduced: the time step must be smaller than the time *
! interval of the wind fields used for interpolation. *
! For random walk simulations, these are the only time step criteria. *
! For the other options, the time step is also limited by the Lagrangian *
! time scale. *
! *
! Author: A. Stohl *
! *
! 16 December 1997 *
! *
! Literature: *
! *
!*****************************************************************************
! *
! Variables: *
! h [m] Mixing height *
! lwindinterv [s] time interval between two wind fields *
! itime [s] current temporal position *
! ldt [s] Suggested time step for next integration *
! ladvance [s] Total integration time period *
! rannumb(maxrand) normally distributed random variables *
! up,vp,wp random velocities due to turbulence *
! usig,vsig,wsig uncertainties of wind velocities due to interpolation *
! usigold,vsigold,wsigold like usig, etc., but for the last time step *
! xt,yt,zt Next time step's spatial position of trajectory *
! *
! *
! Constants: *
! cfl factor, by which the time step has to be smaller than *
! the spatial CFL-criterion *
! cflt factor, by which the time step has to be smaller than *
! the temporal CFL-criterion *
! *
!*****************************************************************************
use par_mod
use com_mod
use interpol_mod
use hanna_mod
implicit none
integer :: itime
integer :: ldt,nrand
integer(kind=2) :: icbt
real :: zt,dz,dz1,dz2,up,vp,wp,usigold,vsigold,wsigold,ran3
real(kind=dp) :: xt,yt
save idummy
integer :: idummy = -7
icbt=1 ! initialize particle to "no reflection"
nrand=int(ran3(idummy)*real(maxrand-1))+1
!******************************
! 2. Interpolate necessary data
!******************************
! Compute maximum mixing height around particle position
!*******************************************************
ix=int(xt)
jy=int(yt)
ixp=ix+1
jyp=jy+1
h=max(hmix(ix ,jy ,1,memind(1)), &
hmix(ixp,jy ,1,memind(1)), &
hmix(ix ,jyp,1,memind(1)), &
hmix(ixp,jyp,1,memind(1)), &
hmix(ix ,jy ,1,memind(2)), &
hmix(ixp,jy ,1,memind(2)), &
hmix(ix ,jyp,1,memind(2)), &
hmix(ixp,jyp,1,memind(2)))
zeta=zt/h
!*************************************************************
! If particle is in the PBL, interpolate once and then make a
! time loop until end of interval is reached
!*************************************************************
if (zeta.le.1.) then
call interpol_all(itime,real(xt),real(yt),zt)
! Vertical interpolation of u,v,w,rho and drhodz
!***********************************************
! Vertical distance to the level below and above current position
! both in terms of (u,v) and (w) fields
!****************************************************************
dz1=zt-height(indz)
dz2=height(indzp)-zt
dz=1./(dz1+dz2)
u=(dz1*uprof(indzp)+dz2*uprof(indz))*dz
v=(dz1*vprof(indzp)+dz2*vprof(indz))*dz
w=(dz1*wprof(indzp)+dz2*wprof(indz))*dz
! Compute the turbulent disturbances
! Determine the sigmas and the timescales
!****************************************
if (turbswitch) then
call hanna(zt)
else
call hanna1(zt)
endif
! Determine the new diffusivity velocities
!*****************************************
if (nrand+2.gt.maxrand) nrand=1
up=rannumb(nrand)*sigu
vp=rannumb(nrand+1)*sigv
wp=rannumb(nrand+2)
if (.not.turbswitch) wp=wp*sigw
! Determine time step for next integration
!*****************************************
if (turbswitch) then
ldt=int(min(tlw,h/max(2.*abs(wp*sigw),1.e-5), &
0.5/abs(dsigwdz),600.)*ctl)
else
ldt=int(min(tlw,h/max(2.*abs(wp),1.e-5),600.)*ctl)
endif
ldt=max(ldt,mintime)
usig=(usigprof(indzp)+usigprof(indz))/2.
vsig=(vsigprof(indzp)+vsigprof(indz))/2.
wsig=(wsigprof(indzp)+wsigprof(indz))/2.
else
!**********************************************************
! For all particles that are outside the PBL, make a single
! time step. Only horizontal turbulent disturbances are
! calculated. Vertical disturbances are reset.
!**********************************************************
! Interpolate the wind
!*********************
call interpol_wind(itime,real(xt),real(yt),zt)
! Compute everything for above the PBL
! Assume constant turbulent perturbations
!****************************************
ldt=abs(lsynctime)
if (nrand+1.gt.maxrand) nrand=1
up=rannumb(nrand)*0.3
vp=rannumb(nrand+1)*0.3
nrand=nrand+2
wp=0.
sigw=0.
endif
!****************************************************************
! Add mesoscale random disturbances
! This is done only once for the whole lsynctime interval to save
! computation time
!****************************************************************
! It is assumed that the average interpolation error is 1/2 sigma
! of the surrounding points, autocorrelation time constant is
! 1/2 of time interval between wind fields
!****************************************************************
if (nrand+2.gt.maxrand) nrand=1
usigold=rannumb(nrand)*usig
vsigold=rannumb(nrand+1)*vsig
wsigold=rannumb(nrand+2)*wsig
end subroutine initialize
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