120 Keith Haines
14-DIMENSIONAL VARIATIONAL ASSIMILATION
..
Iterate back and forth for best Trajectory
Best Model Trajectory
Observations
________ - - - -Original trajectory
TIME
FIND INITIAL STATE FOR BEST TRAJECTORY.
TRAJECTORY BETWEEN OBSERVATIONS INVOLVES
ADVECTION = WATER DISPLACEMENTS (ADIABATIC)
4-D VAR. EXPENSIVE
I 3-DIMENSIONAL : SEQUENTIAL ASSIMILATION WITH DISPLACEMENTS I
Single model integration
~~
similation achieved by
Water Displacements
T_o
TIME
~
ENTIRE TRAJECTORY MAINLY ADVECTIVE
ASSUMES INTEGRATED WATER PROPERTIES AT T_o ARE OK
Fig. 7.1 Schematic of the 4DVar and 3D Sequential data assimilation methods. In the
sequential method the adiabatic displacements at assimilation times are emphasised.