The ECMWF mediumrange prediction models development of the numerical formulations and the impact of increased resolution
 A. J. Simmons,
 D. M. Burridge,
 M. Jarraud,
 C. Girard,
 W. Wergen
 … show all 5 hide
Rent the article at a discount
Rent now* Final gross prices may vary according to local VAT.
Get AccessSummary
An outline is given of the numerical formulations that have been utilized for mediumrange prediction at the European Centre for MediumRange Weather Forecasts. The sigmacoordinate gridpoint model adopted for the first phase of operational forecasting, and the hybridcoordinate spectral model which replaced it, are described. Particular emphasis is placed on aspects of the timestepping employed in the spectral model. It is shown how a semiimplicit treatment of the zonal advection of vorticity and specific humidity, and selective use of enhanced horizontal diffusion, enables timesteps to be used which are well over 50% longer than would otherwise be possible in a spectral model with a classical semiimplicit treatment of gravitywave terms, with negligible computational cost and negligible impact on forecast accuracy, at T 106 resolution at least. Some discussion of the stability of the semiimplicit gravitywave scheme is also included.
The experimental evidence which led to the operational change from the gridpoint to the spectral model is summarized, and the sensitivity of forecasts to the horizontal resolution of the spectral model is illustrated. Both the change in method and increases in resolution result in systematic improvements in the details of cyclone development, and they occasionally have major beneficial impact on the evolution of the forecast in the medium range. Conventional objective verification indicates a much smaller mean improvement of T 106 resolution over T 63 than of T 63 over T 42, although the advantage of T 106 is nevertheless clearcut. This advantage is more than confirmed by synoptic assessment. Scope for further improvement is indicated by first results from global forecasts with a resolution of T 159. Indications of sensitivity to the magnitude of horizontal diffusion and the resolution of the model orography are also given.
The spectral model was initially used operationally with a 16level vertical resolution, and the uppermost level at which prognostic variables were held was 25 mb. The results which justified a subsequent change to 19 levels, with increased stratospheric resolution and a 10 mb top level, are presented. In this case the principal mediumrange forecast improvement came about because better initial analyses could be produced when the 19level model was used in data assimilation.
 Arakawa, A., Lamb, V. R., 1977: Computational design of the basic dynamical processes of the UCLA general circulation model.Methods in Computational Physics, Vol. 17,General Circulation of the Atmosphere, ed. by J. Chang, Ac. Press, 173–265.
 Asselin, R., 1972: Frequency filter for time integrations.Mon. Wea. Rev.,100, 487–490.
 Atlas, R., Ghil, M., Halem, M., 1982: The effect of model resolution and satellite sounding data on GLS model forecasts.Mon. Wea. Rev.,110, 662–682.
 Baede, A. P. M., Jarraud, M., Cubasch, U., 1979: Adiabatic formulation and organization of ECMWF's spectral model. ECMWF Tech. Rep. No. 15, 40 pp.
 Bates, J. R., McDonald, A., 1982: Multiplyupstream semiLagrangian advective schemes: analysis and application to a multilevel primitiveequation model.Mon. Wea. Rev.,110, 1831–1842.
 Bengtsson, L., 1981: Numerical prediction of atmospheric blocking—A case study.Tellus,33, 19–42.
 Bourke, W., 1974: A multilevel spectral model. I: Formulation and hemispheric integrations.Mon. Wea. Rev.,102, 687–701.
 Boville, B. A., 1984: The influence of the polar night jet on the tropospheric circulation in a GCM.J. Atmos. Sci.,41, 1132–1142.
 Burridge, D. M., Steppeler, J., Strüfing, R., 1986: Finite element schemes for the vertical discretization of the ECMWF forecast model using linear elements. ECMWF Tech. Rep. No. 54, 48 pp.
 Dell'Osso, 1984: High resolution experiments with the ECMWF model: A case study.Mon. Wea. Rev.,112, 1853–1883.
 Dent, D., 1987: The ECMWF multitasking weather model. Science and Engineering on Cray Supercomputers: Proceedings of the Third International Symposium. Cray Research Inc., Minneapolis, 35–52.
 ECMWF, 1987: Proceedings of 1986 Seminar/Workshop on Observation, theory and modelling of orographic effects. Vol. I. 333 pp.
 Gibson, J. K., 1984: A production multitasking numerical weather prediction model. ECMWF Tech. Memo No. 91, 22 pp.
 Girard, C., Jarraud, M., 1982: Short and medium range forecast differences between a spectral and grid point model. An extensive quasioperational comparison. ECMWF Tech. Rep. No. 32, 178 pp.
 Hoskins, B. J., Simmons, A. J., 1975: A multilayer spectral model and the semiimplicit method.Quart. J. Roy. Meteor. Soc.,101, 637–655.
 Jarraud, M., Girard, C., 1984: An extensive quasioperational comparison between a spectral and a gridpoint model. ECMWF Seminar on Numerical Methods for Numerical Weather Prediction, 5–9 September 1983, Reading, U.K. 61–111.
 Jarraud, M., Simmons, A. J., 1984: The spectral technique. ECMWF Seminar on Numerical Methods for Weather Prediction, 5–9 September 1983, Reading, U.K., Vol. 2, 1–59.
 Jarraud, M., Simmons, A. J., 1985: Development of the high resolution model. ECMWF Tech. Memo. No. 107, 61 pp.
 Jarraud, M., Simmons, A. J., Kanamitsu, M., 1988: Sensitivity of mediumrange weather forecasts to the use of an envelope orography.Quart. J. Roy. Meteor. Soc.,114, 989–1025.
 Lange, A., Hellsten, E., 1984: Results of the WMO/CAS NWP Data Study and Intercomparison Project for Forecasts for the Northern Hemisphere in 1983. WMO/PWPR Publication Series No. 7, Geneva, 1984.
 Machenhauer, B., 1979: The spectral method. GARP Publication, Series No. 17, II, pp. 121–275.
 Miyakoda, K., Strickler, R. F., Nappo, C. J., Baker, P. L., Hembree, G. D., 1971: The effect of horizontal grid resolution in an atmospheric circulation model.J. Atmos. Sci.,28, 481–499.
 Miyakoda, K., Hembree, G. D., Strickler, R. F., Shulman, L., 1972: Cumulative results of extended forecasts experiments. I: Model performance for winter cases.Mon. Wea. Rev.,100, 836–855.
 Phillips, N. A., 1957: A coordinate system having some special advantages for numerical forecasting.J. Meteor.,14, 184–185.
 Radinovic, D., 1986: On the development of orographic cyclones.Quart. J. Roy. Meteor. Soc.,112, 927–951.
 Ritchie, H., 1987: SemiLagrangian advection on a Gaussian grid.Mon. Wea. Rev.,115, 608–619.
 Ritter, B., 1984: The impact of an alternative treatment of infrared radiation on the performance of the ECMWF model. In:IRS '84; Current Problems in Atmospheric Radiation. Ed. G. Fiocco. Deepak, Hampton, Virginia, 277–280.
 Robert, A., 1981: Stable numerical integration scheme for the primitive meteorological equations.AtmosphereOcean,19, 35–46.
 Robert, A. J., Hendersen, J., Turnbull, C., 1972: An implicit time integration scheme for baroclinic models of the atmosphere.Mon. Wea. Rev.,100, 329–335.
 Robert, A., Yee, T. L., Ritchie, H., 1985: A semiLagrangian and semiimplicit numerical integration scheme for multilevel atmospheric models.Mon. Wea. Rev.,113, 388–394.
 Sadourny, R., 1975: Compressible flows on a sphere.J. Atmos. Sci.,32, 2103–2110.
 Simmons, A. J., 1983: Adiabatic formulation of the ECMWF forecasting system. ECMWF Seminar on Interpretation of Numerical Weather Prediction Products, 13–17 September 1982, Reading, U.K., 59–81.
 Simmons, A. J., 1986: Numerical prediction: some results from operational forecasting at ECMWF.Adv. Geophys. 29, 305–338.
 Simmons, A. J., 1987: Orography and the development of the ECMWF forecast model. ECMWF Seminar on Observation, Theory and Modelling of Orographic Effects, 15–19 September, 1987, Reading, U.K., Vol. 2, 129–163.
 Simmons, A. J., Burridge, D. M., 1981: An energy and angular momentum conserving vertical finite difference scheme and hybrid vertical coordinates.Mon. Wea. Rev.,109, 758–766.
 Simmons, A. J., Hoskins, B. J., Burridge, D. M., 1978: Stability of the semiimplicit method of time integration.Mon. Wea. Rev.,106, 405–412.
 Simmons, A. J., Jarraud, M., 1984: The design and performance of the new ECMWF operational model. ECMWF Seminar on Numerical Methods for Weather Prediction, 5–9 September 1983, Reading, U.K., Vol. 2, 113–164.
 Simmons, A. J., Strüfing, R., 1983: Numerical forecasts of stratospheric warming events using a model with a hybrid vertical coordinate.Quart. J. Roy. Meteor. Soc.,109, 81–111.
 Staniforth, A. N., Temperton, C., 1986: Semiimplicit semiLangrangian schemes for a barotropic finiteelement regional model.Mon. Wea. Rev.,114, 2078–2090.
 Steppeler, J., 1986: Finite element scheme for the vertical discretization of the ECMWF forecast model using quadratic and cubic elements. ECMWF Tech. Rep. No. 55, 59 pp.
 Steppeler, J., 1988: A Galerkin finiteelement spectral weather forecast model in hybrid coordinates.Computers and Mathematics with Applications: Series B,16, 23–30.
 Tibaldi, S., Ji, L. R., 1983: On the effect of model resolution on numerical simulation of blocking.Tellus,35 A, 28–38.
 Tiedtke, M., Geleyn, J.F., Hollingsworth, A., Louis, J.F., 1979: ECMWF model parameterisation of subgrid scale processes. ECMWF Tech. Rep. No. 10, 46 pp.
 Tiedtke, M., Slingo, J., 1985: Development of the operational parameterization scheme. ECMWF Tech. Memo. No. 108, 38 pp.
 Tiedtke, M., Heckley, W., Slingo, J., 1988: Tropical forecasting at ECMWF: The influence of physical parametrization on the mean structure of forecasts and analysis.Quart. J. Roy. Meteor. Soc.,114, 639–664.
 Wergen, W., 1987: Diabatic nonlinear normal model initialization for a spectral model with a hybrid vertical coordinate. ECMWF Tech. Rep. No. 59, 83 pp.
 Williamson, D. L., 1978: The relative importance of resolution, accuracy and diffusion in shortrange forecasts with the NCAR global circulation model.Mon. Wea. Rev.,106, 69–88.
 Title
 The ECMWF mediumrange prediction models development of the numerical formulations and the impact of increased resolution
 Journal

Meteorology and Atmospheric Physics
Volume 40, Issue 13 , pp 2860
 Cover Date
 19890301
 DOI
 10.1007/BF01027467
 Print ISSN
 01777971
 Online ISSN
 14365065
 Publisher
 SpringerVerlag
 Additional Links
 Topics
 Authors

 A. J. Simmons ^{(1)}
 D. M. Burridge ^{(1)}
 M. Jarraud ^{(1)}
 C. Girard ^{(1)}
 W. Wergen ^{(1)}
 Author Affiliations

 1. European Centre for MediumRange Weather Forecasts, Shinfield Park, Reading, Berkshire, U.K.