Hobart

Seminar Abstract

Friday 10 July, 11.30am (Tas time)
CSIRO Auditorium, Hobart

Terence O'Kane
Ocean Data Assimilation Scientist
CSIRO Marine & Atmospheric Research

Turbulence closures, prediction and data assimilation in nonlinear geophysical flows

Using deterministic forecasts the early pioneers of numerical weather prediction tried to establish the theoretical limits to atmospheric predictability in terms of the divergence of pairs of initially close states. Over time, not just weather forecasting but the prediction of nonlinear dynamical systems in general, has come to be regarded as a statistical problem of predicting the probability density function of states or, equivalently, of calculating the moments of state variables and as such is formally identical to the closure problem that arises in statistical approaches to turbulence. The inherently chaotic nature of geophysical systems such as the oceans and atmosphere, combined with errors in the observed initial conditions inevitably leads to the failure of deterministic forecasts. In numerical weather prediction and data assimilation for large numerical models, with millions of variables, calculating the full covariance matrices of the background errors as they evolve with time remains a very difficult problem. Ensemble methods estimate the flow dependent background covariance matrices by construction from ensembles of short term forecasts with slightly differing initial conditions. Recent approaches endeavour to generate independent initial perturbations as fast growing disturbances with structures and growth rates typical of the analysis errors. That is the initial perturbations contain flow dependent instabilities and hence information about the inherent predictability of the flow. In this talk I will describe current state of the art methods in numerical weather prediction / assimilation, relevant to both the oceans and the atmosphere, and discuss the unique insights that turbulence closure theory can bring to this problem of fundamental importance.

Seminar Recording

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Location:
CSIRO = Marine Laboratories Auditorium, Castray Esplanade, Hobart

For further information, or to schedule a seminar, contact:
To schedule a seminar, contact:
Clothilde Langlais, (Oceanographic seminars) CSIRO Marine and Atmospheric Research (03) 6232 5399
Natalie Kelly, (Biology/Modelling seminars) CSIRO Marine and Atmospheric Research 0438 452 483
Jillian Enraght-Moony, (seminar administrator) CSIRO Marine and Atmospheric Research (03) 6232 5320
Communications Manager, Antarctic Climate and Ecosystems CRC (03) 6226 2265
Margaret Hazelwood, Institute of Antarctic and Southern Ocean Studies (IASOS) University of Tasmania (03) 6226 2971

Last updated 21/07/09