Seamless modelling, whereby a single model family can be used for prediction across a range of timescales (from weather forecasting to climate change), has been at the heart of the Met Office strategy for weather and climate prediction since 1990.
The Met Office Unified Model, abbreviated in the literature to MetUM, is the numerical modelling system developed and used at the Met Office. It is 'seamless' in that different configurations of the same model are used across all time and space scales. The different configurations are each designed to best represent the processes which have most influence on the timescale of interest. For example, for accurate climate predictions the use of a coupled ocean model is essential, while for short-range weather forecasting a higher resolution atmospheric model may be more beneficial than running a costly ocean component. The current Unified Model family is illustrated in the figure.
Some benefits of using a seamless modelling system:
efficiency - by developing only one system, duplicated effort is reduced;
understanding - a seamless system allows us to learn about climate model performance and error growth from well constrained, observed and initialised shorter range predictions;
confidence - using the same model at different resolutions gives us confidence that the driving mechanisms within models are consistent with each other;
synergy - advances in climate science can improve weather forecasts and vice-versa.
History of Unified Model development Enlarge
The Unified Model is continually developed (see figure), taking advantage of improved understanding of atmospheric processes and steadily increasing supercomputer power. The latest version of the atmospheric model uses non-hydrostatic dynamics with semi-lagrangian advection and semi-implicit time stepping. It is a grid point model with the ability to run with a rotated pole and variable horizontal grid. A number of sub-grid scale processes are represented, including convection, boundary layer turbulence, radiation, cloud, microphysics and orographic drag. It can be run as a global model, or a limited area model and can also be coupled to land surface, ocean models, wave models, chemistry and Earth system components.
Different configurations of the Unified Model are described here:
The Met Office Unified Model is available for external use under licence. A number of research organisations and national meteorological services use the Unified Model in collaboration with the Met Office to undertake basic atmospheric process research, produce forecasts, develop the Unified Model code and build and evaluate Earth System Models.
Further information on how to apply for a licence, as well as the opportunities and support available for collaboration can be found on the Met Office Unified Model collaboration page.