! source file: /usr/local/models/UVic_ESCM/2.9/source/common/accel.h
!======================= include file "accel.h" ========================
! depth dependent tracer timestep acceleration multipliers used to
! hasten the convergence to equilibrium of the deeper portions of
! ocean-climate models.
! accelerate abyssal processes by varying the length of the tracer
! timestep with depth. by using longer timesteps at depth, one can
! in effect reduce the heat capacity of the deeper levels and speed
! convergence to equilibrium.
! note:
! by applying this method, one is assuming that there is a single
! steady-state solution to the model being considered.
! also, since the diagnostic timestep calculations of "termbt" do
! not attempt to account for depth variant timestep lengths, the
! truncation error reported will increase, because it will include
! the tracer changes due to variations in "dtxcel".
! reference:
! Bryan, K., 1984: accelerating the convergence to equilibrium
! of ocean climate models, J. Phys. Oceanogr., 14, 666-673.
! ("dtxcel" here is the same as 1/gamma in the above reference)
! set "dtxcel" to 1.0 at the surface and for upper levels not
! to be accelerated
! set "dtxcel" to values greater than 1.0 at deeper levels to
! accelerate convergence if above requirements are met
! dtxcel = model level dependent tracer timestep multipliers
! dtxsqr = square root of "dtxcel" (used in computation of
! maximum slope constraint for isopycnal mixing)
! dztxcl = layer thickness divided by the timestep multiplier
! (needed for convection code)
! dzwxcl = multiplication factor relating to the vertical
! distance between ts points, scaled according
! to timestep multipliers for use in convection code
real dtxcel, dtxsqr, dztxcl, dzwxcl
common /accel/ dtxcel(km)
common /accel/ dtxsqr(km)
common /accel/ dztxcl(km), dzwxcl(km)