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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 advance(itime,nrelpoint,ldt,up,vp,wp, &
usigold,vsigold,wsigold,nstop,xt,yt,zt,prob,icbt)
! i i i/oi/oi/o
! i/o i/o i/o o i/oi/oi/o i/o i/o
!*****************************************************************************
! *
! Calculation of turbulent particle trajectories utilizing a *
! zero-acceleration scheme, which is corrected by a numerically more *
! accurate Petterssen scheme whenever possible. *
! *
! Particle positions are read in, incremented, and returned to the calling *
! program. *
! *
! In different regions of the atmosphere (PBL vs. free troposphere), *
! different parameters are needed for advection, parameterizing turbulent *
! velocities, etc. For efficiency, different interpolation routines have *
! been written for these different cases, with the disadvantage that there *
! exist several routines doing almost the same. They all share the *
! included file 'interpol_mod'. The following *
! interpolation routines are used: *
! *
! interpol_all(_nests) interpolates everything (called inside the PBL) *
! interpol_misslev(_nests) if a particle moves vertically in the PBL, *
! additional parameters are interpolated if it *
! crosses a model level *
! interpol_wind(_nests) interpolates the wind and determines the *
! standard deviation of the wind (called outside *
! PBL) also interpolates potential vorticity *
! interpol_wind_short(_nests) only interpolates the wind (needed for the *
! Petterssen scheme) *
! interpol_vdep(_nests) interpolates deposition velocities *
! *
! *
! Author: A. Stohl *
! *
! 16 December 1997 *
! *
! Changes: *
! *
! 8 April 2000: Deep convection parameterization *
! *
! May 2002: Petterssen scheme introduced *
! *
!*****************************************************************************
! *
! Variables: *
! icbt 1 if particle not transferred to forbidden state, *
! else -1 *
! dawsave accumulated displacement in along-wind direction *
! dcwsave accumulated displacement in cross-wind direction *
! dxsave accumulated displacement in longitude *
! dysave accumulated displacement in latitude *
! h [m] Mixing height *
! lwindinterv [s] time interval between two wind fields *
! itime [s] time at which this subroutine is entered *
! itimec [s] actual time, which is incremented in this subroutine *
! href [m] height for which dry deposition velocity is calculated *
! ladvance [s] Total integration time period *
! ldirect 1 forward, -1 backward *
! ldt [s] Time step for the next integration *
! lsynctime [s] Synchronisation interval of FLEXPART *
! ngrid index which grid is to be used *
! nrand index for a variable to be picked from rannumb *
! nstop if > 1 particle has left domain and must be stopped *
! prob probability of absorption due to dry deposition *
! rannumb(maxrand) normally distributed random variables *
! rhoa air density *
! rhograd vertical gradient of the air density *
! up,vp,wp random velocities due to turbulence (along wind, cross *
! wind, vertical wind *
! usig,vsig,wsig mesoscale wind fluctuations *
! usigold,vsigold,wsigold like usig, etc., but for the last time step *
! vdepo Deposition velocities for all species *
! xt,yt,zt Particle position *
! *
!*****************************************************************************
use point_mod
use par_mod
use com_mod
use interpol_mod
use hanna_mod
use cmapf_mod
implicit none
real(kind=dp) :: xt,yt
real :: zt,xts,yts,weight
integer :: itime,itimec,nstop,ldt,i,j,k,nrand,loop,memindnext
integer :: ngr,nix,njy,ks,nsp,nrelpoint
real :: dz,dz1,dz2,xlon,ylat,xpol,ypol,gridsize
real :: ru,rv,rw,dt,ux,vy,cosfact,xtn,ytn,tropop
real :: prob(maxspec),up,vp,wp,dxsave,dysave,dawsave
real :: dcwsave
real :: usigold,vsigold,wsigold,r,rs
real :: uold,vold,wold,vdepo(maxspec)
!real uprof(nzmax),vprof(nzmax),wprof(nzmax)
!real usigprof(nzmax),vsigprof(nzmax),wsigprof(nzmax)
!real rhoprof(nzmax),rhogradprof(nzmax)
real :: rhoa,rhograd,ran3,delz,dtf,rhoaux,dtftlw,uxscale,wpscale
integer(kind=2) :: icbt
real,parameter :: eps=nxmax/3.e5,eps2=1.e-9
!!! CHANGE: TEST OF THE WELL-MIXED CRITERION
! integer,parameter :: iclass=10
! real(kind=dp) :: zacc,tacc,t(iclass),th(0:iclass),hsave
! logical dump
! save zacc,tacc,t,th,hsave,dump
!!! CHANGE
integer :: idummy = -7
real :: settling = 0.
!!! CHANGE: TEST OF THE WELL-MIXED CRITERION
!if (idummy.eq.-7) then
!open(550,file='WELLMIXEDTEST')
!do 17 i=0,iclass
!7 th(i)=real(i)/real(iclass)
!endif
!!! CHANGE
nstop=0
do i=1,nmixz
indzindicator(i)=.true.
end do
if (DRYDEP) then ! reset probability for deposition
do ks=1,nspec
depoindicator(ks)=.true.
prob(ks)=0.
end do
endif
dxsave=0. ! reset position displacements
dysave=0. ! due to mean wind
dawsave=0. ! and turbulent wind
dcwsave=0.
itimec=itime
nrand=int(ran3(idummy)*real(maxrand-1))+1
! Determine whether lat/long grid or polarstereographic projection
! is to be used
! Furthermore, determine which nesting level to be used
!*****************************************************************
if (nglobal.and.(yt.gt.switchnorthg)) then
ngrid=-1
else if (sglobal.and.(yt.lt.switchsouthg)) then
ngrid=-2
else
ngrid=0
do j=numbnests,1,-1
if ((xt.gt.xln(j)+eps).and.(xt.lt.xrn(j)-eps).and. &
(yt.gt.yln(j)+eps).and.(yt.lt.yrn(j)-eps)) then
ngrid=j
goto 23
endif
end do
23 continue
endif
!***************************
! Interpolate necessary data
!***************************
if (abs(itime-memtime(1)).lt.abs(itime-memtime(2))) then
memindnext=1
else
memindnext=2
endif
! Determine nested grid coordinates
!**********************************
if (ngrid.gt.0) then
xtn=(xt-xln(ngrid))*xresoln(ngrid)
ytn=(yt-yln(ngrid))*yresoln(ngrid)
ix=int(xtn)
jy=int(ytn)
nix=nint(xtn)
njy=nint(ytn)
else
ix=int(xt)
jy=int(yt)
nix=nint(xt)
njy=nint(yt)
endif
ixp=ix+1
jyp=jy+1
! Compute maximum mixing height around particle position
!*******************************************************
h=0.
if (ngrid.le.0) then
do k=1,2
do j=jy,jyp
do i=ix,ixp
if (hmix(i,j,1,k).gt.h) h=hmix(i,j,1,k)
end do
end do
end do
tropop=tropopause(nix,njy,1,1)
else
do k=1,2
do j=jy,jyp
do i=ix,ixp
if (hmixn(i,j,1,k,ngrid).gt.h) h=hmixn(i,j,1,k,ngrid)
end do
end do
end do
tropop=tropopausen(nix,njy,1,1,ngrid)
endif
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
! BEGIN TIME LOOP
!================
loop=0
100 loop=loop+1
if (method.eq.1) then
ldt=min(ldt,abs(lsynctime-itimec+itime))
itimec=itimec+ldt*ldirect
else
ldt=abs(lsynctime)
itimec=itime+lsynctime
endif
dt=real(ldt)
zeta=zt/h
if (loop.eq.1) then
if (ngrid.le.0) then
xts=real(xt)
yts=real(yt)
call interpol_all(itime,xts,yts,zt)
else
call interpol_all_nests(itime,xtn,ytn,zt)
endif
else
! Determine the level below the current position for u,v,rho
!***********************************************************
do i=2,nz
if (height(i).gt.zt) then
indz=i-1
indzp=i
goto 6
endif
end do
6 continue
! If one of the levels necessary is not yet available,
! calculate it
!*****************************************************
do i=indz,indzp
if (indzindicator(i)) then
if (ngrid.le.0) then
call interpol_misslev(i)
else
call interpol_misslev_nests(i)
endif
endif
end do
endif
! 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
!****************************************************************
dz=1./(height(indzp)-height(indz))
dz1=(zt-height(indz))*dz
dz2=(height(indzp)-zt)*dz
u=dz1*uprof(indzp)+dz2*uprof(indz)
v=dz1*vprof(indzp)+dz2*vprof(indz)
w=dz1*wprof(indzp)+dz2*wprof(indz)
rhoa=dz1*rhoprof(indzp)+dz2*rhoprof(indz)
rhograd=dz1*rhogradprof(indzp)+dz2*rhogradprof(indz)
! 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
!*****************************************
! Horizontal components
!**********************
if (nrand+1.gt.maxrand) nrand=1
if (dt/tlu.lt..5) then
up=(1.-dt/tlu)*up+rannumb(nrand)*sigu*sqrt(2.*dt/tlu)
else
ru=exp(-dt/tlu)
up=ru*up+rannumb(nrand)*sigu*sqrt(1.-ru**2)
endif
if (dt/tlv.lt..5) then
vp=(1.-dt/tlv)*vp+rannumb(nrand+1)*sigv*sqrt(2.*dt/tlv)
else
rv=exp(-dt/tlv)
vp=rv*vp+rannumb(nrand+1)*sigv*sqrt(1.-rv**2)
endif
nrand=nrand+2
if (nrand+ifine.gt.maxrand) nrand=1
rhoaux=rhograd/rhoa
dtf=dt*fine
dtftlw=dtf/tlw
! Loop over ifine short time steps for vertical component
!********************************************************
do i=1,ifine
! Determine the drift velocity and density correction velocity
!*************************************************************
if (turbswitch) then
if (dtftlw.lt..5) then
wp=((1.-dtftlw)*wp+rannumb(nrand+i)*sqrt(2.*dtftlw) &
+dtf*(dsigwdz+rhoaux*sigw))*real(icbt)
else
rw=exp(-dtftlw)
wp=(rw*wp+rannumb(nrand+i)*sqrt(1.-rw**2) &
+tlw*(1.-rw)*(dsigwdz+rhoaux*sigw))*real(icbt)
endif
delz=wp*sigw*dtf
else
rw=exp(-dtftlw)
wp=(rw*wp+rannumb(nrand+i)*sqrt(1.-rw**2)*sigw &
+tlw*(1.-rw)*(dsigw2dz+rhoaux*sigw**2))*real(icbt)
delz=wp*dtf
endif
!****************************************************
! Compute turbulent vertical displacement of particle
!****************************************************
if (abs(delz).gt.h) delz=mod(delz,h)
! Determine if particle transfers to a "forbidden state" below the ground
! or above the mixing height
!************************************************************************
if (delz.lt.-zt) then ! reflection at ground
icbt=-1
zt=-zt-delz
else if (delz.gt.(h-zt)) then ! reflection at h
icbt=-1
zt=-zt-delz+2.*h
else ! no reflection
icbt=1
zt=zt+delz
endif
if (i.ne.ifine) then
zeta=zt/h
call hanna_short(zt)
endif
end do
nrand=nrand+i
! 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))*ctl)
else
ldt=int(min(tlw,h/max(2.*abs(wp),1.e-5))*ctl)
endif
ldt=max(ldt,mintime)
! If particle represents only a single species, add gravitational settling
! velocity. The settling velocity is zero for gases, or if particle
! represents more than one species
!*************************************************************************
if (mdomainfill.eq.0) then
do nsp=1,nspec
if (xmass(nrelpoint,nsp).gt.eps2) goto 887
end do
887 nsp=min(nsp,nspec)
!!$ if (density(nsp).gt.0.) &
!!$ call get_settling(itime,xts,yts,zt,nsp,settling) !old
if (density(nsp).gt.0.) &
call get_settling(itime,real(xt),real(yt),zt,nsp,settling) !bugfix
w=w+settling
endif
! Horizontal displacements during time step dt are small real values compared
! to the position; adding the two, would result in large numerical errors.
! Thus, displacements are accumulated during lsynctime and are added to the
! position at the end
!****************************************************************************
dxsave=dxsave+u*dt
dysave=dysave+v*dt
dawsave=dawsave+up*dt
dcwsave=dcwsave+vp*dt
zt=zt+w*dt*real(ldirect)
if (zt.gt.h) then
if (itimec.eq.itime+lsynctime) goto 99
goto 700 ! complete the current interval above PBL
endif
!!! CHANGE: TEST OF THE WELL-MIXED CRITERION
!!! These lines may be switched on to test the well-mixed criterion
!if (zt.le.h) then
! zacc=zacc+zt/h*dt
! hsave=hsave+h*dt
! tacc=tacc+dt
! do 67 i=1,iclass
! if ((zt/h.gt.th(i-1)).and.(zt/h.le.th(i)))
! + t(i)=t(i)+dt
!7 continue
!endif
!if ((mod(itime,10800).eq.0).and.dump) then
! dump=.false.
! write(550,'(i6,12f10.3)') itime,hsave/tacc,zacc/tacc,
! + (t(i)/tacc*real(iclass),i=1,iclass)
! zacc=0.
! tacc=0.
! do 68 i=1,iclass
!8 t(i)=0.
! hsave=0.
!endif
!if (mod(itime,10800).ne.0) dump=.true.
!!! CHANGE
! Determine probability of deposition
!************************************
if ((DRYDEP).and.(zt.lt.2.*href)) then
do ks=1,nspec
if (DRYDEPSPEC(ks)) then
if (depoindicator(ks)) then
if (ngrid.le.0) then
call interpol_vdep(ks,vdepo(ks))
else
call interpol_vdep_nests(ks,vdepo(ks))
endif
endif
! correction by Petra Seibert, 10 April 2001
! this formulation means that prob(n) = 1 - f(0)*...*f(n)
! where f(n) is the exponential term
prob(ks)=1.+(prob(ks)-1.)* &
exp(-vdepo(ks)*abs(dt)/(2.*href))
endif
end do
endif
if (zt.lt.0.) zt=min(h-eps2,-1.*zt) ! if particle below ground -> reflection
if (itimec.eq.(itime+lsynctime)) then
usig=0.5*(usigprof(indzp)+usigprof(indz))
vsig=0.5*(vsigprof(indzp)+vsigprof(indz))
wsig=0.5*(wsigprof(indzp)+wsigprof(indz))
goto 99 ! finished
endif
goto 100
! END TIME LOOP
!==============
endif
!**********************************************************
! 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
!*********************
700 continue
if (ngrid.le.0) then
xts=real(xt)
yts=real(yt)
call interpol_wind(itime,xts,yts,zt)
else
call interpol_wind_nests(itime,xtn,ytn,zt)
endif
! Compute everything for above the PBL
! Assume constant, uncorrelated, turbulent perturbations
! In the stratosphere, use a small vertical diffusivity d_strat,
! in the troposphere, use a larger horizontal diffusivity d_trop.
! Turbulent velocity scales are determined based on sqrt(d_trop/dt)
!******************************************************************
ldt=abs(lsynctime-itimec+itime)
dt=real(ldt)
if (zt.lt.tropop) then ! in the troposphere
uxscale=sqrt(2.*d_trop/dt)
if (nrand+1.gt.maxrand) nrand=1
ux=rannumb(nrand)*uxscale
vy=rannumb(nrand+1)*uxscale
nrand=nrand+2
wp=0.
else if (zt.lt.tropop+1000.) then ! just above the tropopause: make transition
weight=(zt-tropop)/1000.
uxscale=sqrt(2.*d_trop/dt*(1.-weight))
if (nrand+2.gt.maxrand) nrand=1
ux=rannumb(nrand)*uxscale
vy=rannumb(nrand+1)*uxscale
wpscale=sqrt(2.*d_strat/dt*weight)
wp=rannumb(nrand+2)*wpscale+d_strat/1000.
nrand=nrand+3
else ! in the stratosphere
if (nrand.gt.maxrand) nrand=1
ux=0.
vy=0.
wpscale=sqrt(2.*d_strat/dt)
wp=rannumb(nrand)*wpscale
nrand=nrand+1
endif
! If particle represents only a single species, add gravitational settling
! velocity. The settling velocity is zero for gases
!*************************************************************************
if (mdomainfill.eq.0) then
do nsp=1,nspec
if (xmass(nrelpoint,nsp).gt.eps2) goto 888
end do
888 nsp=min(nsp,nspec)
!!$ if (density(nsp).gt.0.) &
!!$ call get_settling(itime,xts,yts,zt,nsp,settling) !old
if (density(nsp).gt.0.) &
call get_settling(itime,real(xt),real(yt),zt,nsp,settling) !bugfix
w=w+settling
endif
! Calculate position at time step itime+lsynctime
!************************************************
dxsave=dxsave+(u+ux)*dt
dysave=dysave+(v+vy)*dt
zt=zt+(w+wp)*dt*real(ldirect)
if (zt.lt.0.) zt=min(h-eps2,-1.*zt) ! if particle below ground -> reflection
99 continue
!****************************************************************
! Add mesoscale random disturbances
! This is done only once for the whole lsynctime interval to save
! computation time
!****************************************************************
! Mesoscale wind velocity fluctuations are obtained by scaling
! with the standard deviation of the grid-scale winds surrounding
! the particle location, multiplied by a factor turbmesoscale.
! The autocorrelation time constant is taken as half the
! time interval between wind fields
!****************************************************************
r=exp(-2.*real(abs(lsynctime))/real(lwindinterv))
rs=sqrt(1.-r**2)
if (nrand+2.gt.maxrand) nrand=1
usigold=r*usigold+rs*rannumb(nrand)*usig*turbmesoscale
vsigold=r*vsigold+rs*rannumb(nrand+1)*vsig*turbmesoscale
wsigold=r*wsigold+rs*rannumb(nrand+2)*wsig*turbmesoscale
dxsave=dxsave+usigold*real(lsynctime)
dysave=dysave+vsigold*real(lsynctime)
zt=zt+wsigold*real(lsynctime)
if (zt.lt.0.) zt=-1.*zt ! if particle below ground -> refletion
!*************************************************************
! Transform along and cross wind components to xy coordinates,
! add them to u and v, transform u,v to grid units/second
! and calculate new position
!*************************************************************
call windalign(dxsave,dysave,dawsave,dcwsave,ux,vy)
dxsave=dxsave+ux
dysave=dysave+vy
if (ngrid.ge.0) then
cosfact=dxconst/cos((yt*dy+ylat0)*pi180)
xt=xt+real(dxsave*cosfact*real(ldirect),kind=dp)
yt=yt+real(dysave*dyconst*real(ldirect),kind=dp)
else if (ngrid.eq.-1) then ! around north pole
xlon=xlon0+xt*dx
ylat=ylat0+yt*dy
call cll2xy(northpolemap,ylat,xlon,xpol,ypol)
gridsize=1000.*cgszll(northpolemap,ylat,xlon)
dxsave=dxsave/gridsize
dysave=dysave/gridsize
xpol=xpol+dxsave*real(ldirect)
ypol=ypol+dysave*real(ldirect)
call cxy2ll(northpolemap,xpol,ypol,ylat,xlon)
xt=(xlon-xlon0)/dx
yt=(ylat-ylat0)/dy
else if (ngrid.eq.-2) then ! around south pole
xlon=xlon0+xt*dx
ylat=ylat0+yt*dy
call cll2xy(southpolemap,ylat,xlon,xpol,ypol)
gridsize=1000.*cgszll(southpolemap,ylat,xlon)
dxsave=dxsave/gridsize
dysave=dysave/gridsize
xpol=xpol+dxsave*real(ldirect)
ypol=ypol+dysave*real(ldirect)
call cxy2ll(southpolemap,xpol,ypol,ylat,xlon)
xt=(xlon-xlon0)/dx
yt=(ylat-ylat0)/dy
endif
! If global data are available, use cyclic boundary condition
!************************************************************
if (xglobal) then
if (xt.ge.real(nxmin1)) xt=xt-real(nxmin1)
if (xt.lt.0.) xt=xt+real(nxmin1)
if (xt.le.eps) xt=eps
if (abs(xt-real(nxmin1)).le.eps) xt=real(nxmin1)-eps
endif
! Check position: If trajectory outside model domain, terminate it
!*****************************************************************
if ((xt.lt.0.).or.(xt.ge.real(nxmin1)).or.(yt.lt.0.).or. &
(yt.ge.real(nymin1))) then
nstop=3
return
endif
! If particle above highest model level, set it back into the domain
!*******************************************************************
if (zt.ge.height(nz)) zt=height(nz)-100.*eps
!************************************************************************
! Now we could finish, as this was done in FLEXPART versions up to 4.0.
! However, truncation errors of the advection can be significantly
! reduced by doing one iteration of the Petterssen scheme, if this is
! possible.
! Note that this is applied only to the grid-scale winds, not to
! the turbulent winds.
!************************************************************************
! The Petterssen scheme can only applied with long time steps (only then u
! is the "old" wind as required by the scheme); otherwise do nothing
!*************************************************************************
if (ldt.ne.abs(lsynctime)) return
! The Petterssen scheme can only be applied if the ending time of the time step
! (itime+ldt*ldirect) is still between the two wind fields held in memory;
! otherwise do nothing
!******************************************************************************
if (abs(itime+ldt*ldirect).gt.abs(memtime(2))) return
! Apply it also only if starting and ending point of current time step are on
! the same grid; otherwise do nothing
!*****************************************************************************
if (nglobal.and.(yt.gt.switchnorthg)) then
ngr=-1
else if (sglobal.and.(yt.lt.switchsouthg)) then
ngr=-2
else
ngr=0
do j=numbnests,1,-1
if ((xt.gt.xln(j)+eps).and.(xt.lt.xrn(j)-eps).and. &
(yt.gt.yln(j)+eps).and.(yt.lt.yrn(j)-eps)) then
ngr=j
goto 43
endif
end do
43 continue
endif
if (ngr.ne.ngrid) return
! Determine nested grid coordinates
!**********************************
if (ngrid.gt.0) then
xtn=(xt-xln(ngrid))*xresoln(ngrid)
ytn=(yt-yln(ngrid))*yresoln(ngrid)
ix=int(xtn)
jy=int(ytn)
else
ix=int(xt)
jy=int(yt)
endif
ixp=ix+1
jyp=jy+1
! Memorize the old wind
!**********************
uold=u
vold=v
wold=w
! Interpolate wind at new position and time
!******************************************
if (ngrid.le.0) then
xts=real(xt)
yts=real(yt)
call interpol_wind_short(itime+ldt*ldirect,xts,yts,zt)
else
call interpol_wind_short_nests(itime+ldt*ldirect,xtn,ytn,zt)
endif
if (mdomainfill.eq.0) then
do nsp=1,nspec
if (xmass(nrelpoint,nsp).gt.eps2) goto 889
end do
889 nsp=min(nsp,nspec)
!!$ if (density(nsp).gt.0.) &
!!$ call get_settling(itime+ldt,xts,yts,zt,nsp,settling) !old
if (density(nsp).gt.0.) &
call get_settling(itime+ldt,real(xt),real(yt),zt,nsp,settling) !bugfix
w=w+settling
endif
! Determine the difference vector between new and old wind
! (use half of it to correct position according to Petterssen)
!*************************************************************
u=(u-uold)/2.
v=(v-vold)/2.
w=(w-wold)/2.
! Finally, correct the old position
!**********************************
zt=zt+w*real(ldt*ldirect)
if (zt.lt.0.) zt=min(h-eps2,-1.*zt) ! if particle below ground -> reflection
if (ngrid.ge.0) then
cosfact=dxconst/cos((yt*dy+ylat0)*pi180)
xt=xt+real(u*cosfact*real(ldt*ldirect),kind=dp)
yt=yt+real(v*dyconst*real(ldt*ldirect),kind=dp)
else if (ngrid.eq.-1) then ! around north pole
xlon=xlon0+xt*dx
ylat=ylat0+yt*dy
call cll2xy(northpolemap,ylat,xlon,xpol,ypol)
gridsize=1000.*cgszll(northpolemap,ylat,xlon)
u=u/gridsize
v=v/gridsize
xpol=xpol+u*real(ldt*ldirect)
ypol=ypol+v*real(ldt*ldirect)
call cxy2ll(northpolemap,xpol,ypol,ylat,xlon)
xt=(xlon-xlon0)/dx
yt=(ylat-ylat0)/dy
else if (ngrid.eq.-2) then ! around south pole
xlon=xlon0+xt*dx
ylat=ylat0+yt*dy
call cll2xy(southpolemap,ylat,xlon,xpol,ypol)
gridsize=1000.*cgszll(southpolemap,ylat,xlon)
u=u/gridsize
v=v/gridsize
xpol=xpol+u*real(ldt*ldirect)
ypol=ypol+v*real(ldt*ldirect)
call cxy2ll(southpolemap,xpol,ypol,ylat,xlon)
xt=(xlon-xlon0)/dx
yt=(ylat-ylat0)/dy
endif
! If global data are available, use cyclic boundary condition
!************************************************************
if (xglobal) then
if (xt.ge.real(nxmin1)) xt=xt-real(nxmin1)
if (xt.lt.0.) xt=xt+real(nxmin1)
if (xt.le.eps) xt=eps
if (abs(xt-real(nxmin1)).le.eps) xt=real(nxmin1)-eps
endif
! Check position: If trajectory outside model domain, terminate it
!*****************************************************************
if ((xt.lt.0.).or.(xt.ge.real(nxmin1)).or.(yt.lt.0.).or. &
(yt.ge.real(nymin1))) then
nstop=3
return
endif
! If particle above highest model level, set it back into the domain
!*******************************************************************
if (zt.ge.height(nz)) zt=height(nz)-100.*eps
end subroutine advance
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