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program hadley3 |
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|
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c*** This subroutine calculates analysis errors using greg`s |
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c*** ensemble square root filter, or the traditional ensemble |
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c*** kalman filter. |
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c*** |
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c*** Written by: Sai Ravela |
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c*** Last modified: Feb 2, 2003 |
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|
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implicit none |
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|
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integer i, j, k, ijuli, isteps |
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integer nens ! ensemble size |
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integer iters ! number of iterations |
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integer n ! state size, calculated from |
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integer nx, ny, nz ! physical dimension sizes, and |
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integer nf ! number of observed variables |
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integer mobs, isai |
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integer ii, jj, zob, xob, yob |
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#include "hadley3.h" |
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integer iobsloc(mobs) ! obs locations, in terms of |
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! dimensions in the state vector. |
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! Indicated with the matrix H in KF |
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! literature. |
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! In practical terms, the numbers |
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! the locations of the words in the |
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! pickup file |
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integer indxa |
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real*8 ytrue(n) ! state vector |
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real*8 yobs(mobs) ! current observations of state |
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real*8 ytmp(n) ! tmp state vector |
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real*8 pert(n), R(mobs), yobsfull(n), ave(n), var(n) |
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real*8 xens(n,nens) |
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real*8 var_obs, eps, dt, x |
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real*8 obserr, analerr, distsub, distobs |
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integer iret, system |
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real*4 mask(ny,nx) |
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|
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c*** open some output files |
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open(unit=2,file='test.dat',status='unknown') |
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c open(unit=3,file='fields.dat',status='unknown') |
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|
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c*** initialisations |
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eps=0.0005 ! obs error variance - 1/2 mm/s |
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! only good for u and v |
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! need to vary this for |
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! different variables |
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|
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c*** Here is where you read iobsloc and set the corresponding |
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c variances. |
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call ReadObsLoc(3,mobs,iobsloc) |
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write (*,*) 'iobsloc set',mobs, iobsloc(mobs), nens |
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var_obs=eps**2 |
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do i=1,mobs |
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c why the if/then? |
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if (iobsloc(i) < nx*ny*nz*3) then |
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R(i)=var_obs |
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else |
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R(i) = 0.1 ! 0.9 deg other |
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end if |
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enddo |
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|
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c*** get initial observations -- assumes that model has |
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c already spun up (how long?) |
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|
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write (*,*) 'getting Truth' |
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call ReadPickup(0,n,nx,ny,nz,ytrue) |
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write (*,*) 'got Truth' |
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|
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c*** fantasy observations |
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write (*,*) 'generating observations' |
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call random2(pert,n) |
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yobsfull = ytrue+eps*pert |
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c*** apply observation mask |
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do i = 1,mobs |
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indxa = iobsloc(i) |
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yobs(i) = yobsfull(indxa) |
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end do |
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|
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write (*,*) 'generating ensemble' |
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do i=1,nens |
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call random2(pert,n) |
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do j=1,n |
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xens(j,i)=yobsfull(j)+eps*pert(j) |
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ytmp(j)=xens(j,i) |
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enddo |
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call WritePickUp(i,n,nx,ny,nz,ytmp) |
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enddo |
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|
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c*** main iteration loop |
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do i=1,iters |
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|
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c*** step truth forward |
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write (*,*) 'Stepping Truth' |
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call Model(0) |
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c call ReadPickup(0,n,nx,ny,nz,ytmp) |
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c call WritePickUp(0,n,nx,ny,nz,ytmp) |
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write (*,*) 'Stepped Truth' |
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|
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write (*,*) 'getting Truth' |
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call ReadPickup(0,n,nx,ny,nz,ytrue) |
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write (*,*) 'got Truth' |
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|
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c*** fantasy observations |
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write (*,*) 'generating observations' |
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call random2(pert,n) |
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yobsfull = ytrue+eps*pert |
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c*** apply observation mask |
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do j = 1,mobs |
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indxa = iobsloc(j) |
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yobs(j) = yobsfull(indxa) |
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end do |
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|
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c*** step ensemble forward |
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write (*,*) 'Stepping Ensemble' |
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do j=1,nens |
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call Model(j) |
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call ReadPickUp(j,n,nx,ny,nz,ytmp) |
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do k=1,n |
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xens(k,j)=ytmp(k) |
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enddo |
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enddo |
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write (*,*) 'Stepped Ensemble' |
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|
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|
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call EnSRF3d(xens,yobs,iobsloc,n,mobs,R,nens,nx,ny,nz,mask) |
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|
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do j=0,nens |
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do k=1,n |
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ytmp(k)=xens(k,j) |
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enddo |
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call WritePickUp(j,n,nx,ny,nz,ytmp) |
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enddo |
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|
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|
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c*** get ensemble mean and variance |
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call ranmean2(xens,ave,n,nens) |
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call ranvar(xens,ave,n,nens,var) |
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|
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c*** calculate obs and anal err |
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obserr=distsub(yobs,yobsfull,n) |
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analerr=distsub(yobs,ave,n) |
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write(6,*) "\tOBSERR\t", "\tANALERR" |
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write(6,*) obserr, analerr |
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write(2,*) iters, obserr, analerr |
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write(3,'(250f18.10)') (ave(i), i=1,n) |
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|
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call flush() |
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|
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enddo |
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|
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return |
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end |
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