Custom Query (964 matches)

Some of the tracer advection alogorithms are highly nonlinear and may become unstable when running the tangent linear, representer, and adjoint models. This may affect the convergence of the 4DVar data assimilation algorithms. Therefore, it is possible to choose a simpler (less nonlinear) horizontal and vertical tracer advection scheme, if so desired, for the tangent linear, representer and adjoint models. Notice that this strategy still allows us to use highly nonlinear tracer advection schemes in the basic state upon which the tangent linear and adjoint models are linearized. Also, it allows us to use those schemes that have not been adjointed yet, for example, TS_MPDATA. Recall that basic state trajectory is computed by running the nonlinear model.

The flags below are optional. By default, the same options choosed for the nonlinear model are selected for the tangent linear representer, and adjoint models. However, you have the choice to specify different tracer advection options than the basic state.

• TS_A4HADVECTION_TL: use if 4th-order Akima horizontal advection
• TS_C2HADVECTION_TL: use if 2nd-order centered horizontal advection
• TS_C4HADVECTION_TL: use if 4th-order centered horizontal advection
• TS_U3HADVECTION_TL: use if 3rd-order upstream horiz. advection

• TS_A4VADVECTION_TL: use if 4th-order Akima vertical advection
• TS_C2VADVECTION_TL: use if 2nd-order centered vertical advection
• TS_C4VADVECTION_TL: use if 4th-order centered vertical advection
• TS_SVADVECTION_TL: use if splines vertical advection

Many thanks to Brian Powell for suggesting this strategy.

Corrected the release of new floats. The floats were released twice during two consecutive time steps. The conditional for release needs to be:

       HalfDT=0.5_r8*dt(ng)
       DO l=Lstr,Lend
         IF (.not.bounded(l).and.                                        &
      &      (time(ng)-HalfDT.le.Tinfo(itstr,l).and.                     &
      &       time(ng)+HalfDT.gt.Tinfo(itstr,l))) THEN
           ...
         END IF
       END DO

Previously, we have a dt(ng) instead of HalfDT. This triggered the consecutive release.

To facilitate error tracking the routine interp_floats is now inside of a module. So the arguments to this routine were changed to follow modules rules.

Also corrected a major parallel bug in the vertical random walk. We have been hunting for this bug for days. It was very frustrating since the bug desappeared several times. Well, after all this was a random process. Anyway, the major parallel bug was actually in step3d_t.F when computing the vertical diffusivity gradient. Rats..., I have been looking at the drifters routines for days instead. This one was nasty, it has been in ROMS since its implementation!

The float's vertical random walk is now computed in a separated new module, vwalk_floats.F. This facilitated the predictor/corrector for the float vertical position. It is assumed that the vertical diffusivity and its gradient remains constant during the corrector step. The correction is done only in the float spatial positions. The old forward step is still possible by activating new option VWALK_FORWARD.

Fixed a problem in the plotting package when the input NetCDF variables have more that 15 characters. Also added the logic to plot SiOH4, nanophytoplankton, diatom, microzooplankton, mesozooplankton, opal, and oxygen variables in Data/varid.dat.

Many thanks to Dale Haidvogel for reporting this problem.