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subroutine pvinterpol
& (pv, xt,yt,itime1,itime2,itime, pvint)
C i i i i i i o
C Special interpolation subroutine for pot. vorticity on a small subgrid
C In horizontal direction bilinear interpolation interpolation is used.
C Temporally a linear interpolation is used.
C
C Variables:
C pv (nx,ny,nt) potential vorticity on 2*2*2 subgrid
C xt,yt horizontal position in interval [0:1,0:1]
C to which the interpolation is to be made
C itime1,itime2 time in seconds for which PV is given
C itime time in seconds for which PV is desired
C pvint interpolated value of PV
C
C Author: Petra Seibert
C based on subroutine lininterpol.f by A. Stohl from 30 May 1994
C Date: 3 May 1995
dimension pv(2,2,2), pvt(2)
C bilinear horizontal interpolation
ddx = xt
ddy = yt
rddx = 1.-ddx
rddy = 1.-ddy
C loop over 2 time levels
do 20 n=1,2
pvt(n) = rddx * rddy * pv(1,1,n)
+ + ddx * rddy * pv(2,1,n)
+ +rddx * ddy * pv(1,2,n)
+ + ddx * ddy * pv(2,2,n)
20 continue
C temporal interpolation (linear)
dt1 = float( itime - itime1 )
dt2 = float( itime2 - itime )
pvint = (pvt(1) * dt2 + pvt(2) * dt1) / (dt1 + dt2)
return
end
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