Water column model: 1D model (C1D) (key_ c1d)

The 1D model option simulates a stand alone water column within the 3D NEMO system. It can be applied to the ocean alone or to the ocean-ice system and can include passive tracers or a biogeochemical model. It is set up by defining the position of the 1D water column in the grid (see CONFIG/SHARED/namelist_ref ). The 1D model is a very useful tool (a) to learn about the physics and numerical treatment of vertical mixing processes ; (b) to investigate suitable parameterisations of unresolved turbulence (surface wave breaking, Langmuir circulation, ...) ; (c) to compare the behaviour of different vertical mixing schemes ; (d) to perform sensitivity studies on the vertical diffusion at a particular point of an ocean domain ; (d) to produce extra diagnostics, without the large memory requirement of the full 3D model.

The methodology is based on the use of the zoom functionality over the smallest possible domain : a 3x3 domain centered on the grid point of interest, with some extra routines. There is no need to define a new mesh, bathymetry, initial state or forcing, since the 1D model will use those of the configuration it is a zoom of. The chosen grid point is set in namcfg namelist by setting the jpizoom and jpjzoom parameters to the indices of the location of the chosen grid point.

The 1D model has some specifies. First, all the horizontal derivatives are assumed to be zero, and second, the two components of the velocity are moved on a $T$-point. Therefore, defining key_ c1d changes five main things in the code behaviour:

(1)

the lateral boundary condition routine (lbc_lnk) set the value of the central column of the 3x3 domain is imposed over the whole domain ;

(3)

a call to lbc_lnk is systematically done when reading input data ($i.e.$ in iom.F90) ;

(3)

a simplified stp routine is used (stp_c1d, see step_c1d.F90 module) in which both lateral tendancy terms and lateral physics are not called ;

(4)

the vertical velocity is zero (so far, no attempt at introducing a Ekman pumping velocity has been made) ;

(5)

a simplified treatment of the Coriolis term is performed as $U$- and $V$-points are the same (see dyncor_c1d.F90).

All the relevant _c1d modules can be found in the NEMOGCM/NEMO/OPA_SRC/C1D directory of the NEMO distribution.