Implementation of MPDATA and Isoneutral Diffusion in
Sigma-Coordinate Ocean Models
Jens Debernard
Norwegian Meteorological Insitute, Oslo, Norway
Considered is the implementation of the positive definite advection
scheme MPDATA and a rotated isoneutral diffusion tensor into DNMIs
version of the POM model. The work is motivated by the fact that when
constructing ocean models for use in climate change simulations the
conservation of heat and salt becomes of paramount importance. The
commonly employed leapfrog scheme for advection is severely dispersive
and can produce artificial water masses when used in coarse resolution
simulations. With the non-oscillatory MPDATA algorithm, the situation is
greatly improved.
To further refine the water mass conservation a rotated isoneutral
diffusion tensor is implemented to favorable mixing along density
surfaces and to reduce dianeutral mixing.
The influence of these new implementations on the general model behavior
will be illustrated.