Updated balance operator input parameters

[arango]

Updated the balance operator to specify its input parameters from the s4dvar.in script:

! Number of iterations in the biconjugate gradient algorithm used to solve
! the elliptic equation for sea surface height in the error covariance
! balance operator, [1:Ngrids].

          Nbico == 200

! Parameters used to compute balanced salinity in terms of temperature using
! empirical T-S relationships in the error covariance balance operator,
! [1:Ngrids].

       dTdz_min == 0.001d0                ! minimun dT/dz (Celsius/m)
       ml_depth == 100.0d0                ! mixed-layer depth (m; positive)

Notice that we need as many Nbico iterations are required to decrease the error value of the reference free-surface to 1E-8 or smaller. In many applications Nbico=200 will do the job.

Warning: be aware that there are 4 arrays that are allocated using Nbico and its value maybe constrained by available memory:

• FOURDVAR(ng) % p_r2d (LBi:UBi,LBj:UBj,Nbico(ng))
• FOURDVAR(ng) % r_r2d (LBi:UBi,LBj:UBj,Nbico(ng))
• FOURDVAR(nd) % bp_r2d(LBi:UBi,LBj:UBj,Nbico(ng))
• FOURDVAR(ng) % br_r2d(LBi:UBi,LBj:UBj,Nbico(ng))

All the values are needed in the backward iterations of the adjoint.

I also corrected couple of bugs. Many thanks to Andy more fore reporting and correcting these problems.