Investigations into the predictability of global and limited area ocean models, using the BLUElink ocean forecasting system
Commander Robert Woodham
Director of Meteorology and oceanography from the
Royal Australian Navy and ADFA
Abstract
Small errors in the initial conditions of an oceanic model can grow
rapidly, and destroy the model's forecasting skill. A deterministic
forecast must therefore be considered incomplete unless accompanied by
an estimate of the flow-dependent predictability. In order to introduce
this concept of predictability, the seminar will begin with a review of
stability theory, and its application to error growth in, and
predictability of, global and limited area numerical models of the
ocean. Expected error growth characteristics will be presented, and
methods for identifying the fastest-growing error patterns explained.
Results will then be presented from an application of one such method,
using Empirical Orthogonal Functions (EOFs) to approximate the Jacobian
matrix, and hence identify the fastest growing singular vectors, to a
limited area model set up over an oceanic domain in the vicinity of
Perth. The dependence of the method on the norm used to measure error
growth will be presented. The limited area model used for these studies
is the 'Sparse Hydrodynamic Ocean Code' (SHOC), which is in routine use
by the Royal Australian Navy to provide high-resolution ocean forecasts
over areas of interest to the Australian Defence Force. SHOC is forced
at its open boundaries by the 'BLUElink' global ocean model. The seminar
will conclude with some intended avenues for future study.