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On the use of a predictor–corrector scheme to couple the dynamics with the physical parametrizations in the ECMWF model
Author(s) -
Cullen M. J. P.,
Salmond D. J.
Publication year - 2003
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1256/qj.02.12
Subject(s) - parametrization (atmospheric modeling) , coupling (piping) , scheme (mathematics) , nonlinear system , mathematics , predictor–corrector method , current (fluid) , convection , computer science , range (aeronautics) , statistical physics , mathematical optimization , meteorology , mathematical analysis , physics , aerospace engineering , thermodynamics , mechanical engineering , quantum mechanics , engineering , radiative transfer
Methods of coupling the time integration of the resolved dynamics with the parametrized processes in atmospheric models are an active development area. Many centres have demonstrated strong sensitivity to variations in the methods of coupling in their models. The European Centre for Medium‐Range Weather Forecasts has recently introduced a revised method of coupling which gives significant forecast benefits. Theoretically, optimal methods are difficult to establish because of the mixture of timescales represented within the parametrizations. Implicit methods are well‐suited to achieving coupling between different processes, but are not practical because of the nonlinear switching present in most parametrization schemes. In this paper we show that a predictor–corrector scheme can give some of the advantages of a fully‐implicit scheme. We show that the use of more than one physics evaluation per time step significantly improves the accuracy in a model problem. We also demonstrate the effect of further iterations which, in principle, would converge towards a fully‐implicit scheme. A second iteration has only a small effect on overall performance, but gives a large reduction in the amount of convection. This indicates that the current formulation of convection is not compatible with this type of integration scheme. Copyright © 2003 Royal Meteorological Society