GRANDE CONFÉRENCE RCM2

CONFÉRENCIER / SPEAKER :
Dr. Tim Palmer
European Centre for Medium-Range Weather Forecasts
(ECMWF), Reading (U.K.)

TITRE / TITLE :
Ensemble Prediction of Weather and Climate: A Risky Business

LIEU / LOCATION
McGill University
855 Sherbrooke Street West
Leacock Building - Local 232
Carte : http://www.mcgill.ca/maps/?Building=150

DATE : Jeudi 30 janvier / Thursday January 30, 2003

HEURE / TIME : 17 h / 5 p.m.


RÉSUMÉ / ABSTRACT :

Throughout much of the 20th century, weather prediction was considered a prototypical example of a deterministic initial value problem. However, with the recognition of the chaotic nature of weather and climate, it was realized that forecast accuracy is limited by flow-dependent amplification of inevitable uncertainties both in the initial state and in the computational representation of the equations of climate. As we enter the 21st century, the character of weather and climate prediction has turned from deterministic to probabilistic - from prediction of weather and climate, to weather and climate risk. This change in philosophy has been made possible through the development of so-called ensemble prediction systems - comprising multiple forecasts made with slightly different initial states and slightly different model formulations. It will be shown that such ensemble-based risk forecasts are intrinsically more valuable than single deterministic predictions of uncertain accuracy, for a range of forecast customers. Examples will be given of ensemble-based risk predictions of severe weather and extreme climate variability on timescales of days seasons and decades.



** Il est à noter que cette Grande Conférence sera donnée dans le cadre d'une série de conférences, ouverte à tous, intitulée « Prédiction globale du temps et du climat »

Le jeudi 30 janvier 2003, même adresse.