Maturity of Operational Numerical Weather Prediction: Medium Range
In 1939 Rossby demonstrated the usefulness of the linearized perturbation of the equations of motion for weather prediction and thus made possible the first successful numerical forecasts of the weather by Charney et al. In 1951 Charney wrote a paper on the science of numerical weather prediction (N...
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Veröffentlicht in: | Bulletin of the American Meteorological Society 1998-12, Vol.79 (12), p.2753-2769 |
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Zusammenfassung: | In 1939 Rossby demonstrated the usefulness of the linearized perturbation of the equations of motion for weather prediction and thus made possible the first successful numerical forecasts of the weather by Charney et al. In 1951 Charney wrote a paper on the science of numerical weather prediction (NWP), where he predicted with remarkable vision how NWP would evolve until the present. In the 1960’s Lorenz discovered that the chaotic nature of the atmosphere imposes a finite limit of about two weeks to weather predictability. At that time this fundamental discovery was “only of academic interest” and not really relevant to operational weather forecasting, since at that time the accuracy of even a 2-day forecast was rather poor. Since then, however, computer-based forecasts have improved so much that Lorenz’s limit of predictability is starting to become attainable in practice, especially with ensemble forecasting, and the predictabilty of longer-lasting phenomena such as El Niño is beginning to be successfully exploited.
The skill of operational weather forecasts has at least doubled over the last two decades. This improvement has taken place relatively steadily, driven by a large number of scientific and computational developments, especially in the area of NWP. It has taken place in all the operational NWP centers, as friendly competition and information sharing make scientific improvements take place faster than they would in a single center. Because the improvements have occurred steadily, rather than suddenly, the overall increase in forecast skill due to NWP has not been clearly recognized by the media and the public despite the impact that improved forecasts have on the national economy and on the lives of every American.
In this paper the authors review several measures of operational forecast skill that quantify improvements in NWP at the National Centers for Environmental Prediction (NCEP, formerly the National Meteorological Center) of the National Weather Service, although they are representative of improvements in all major NWP operational centers. The authors point out that there are three major requirements for improved numerical weather prediction: better atmospheric models, better observational data, and better methods for data assimilation. These improvements are generally very computer intensive and can only be made operational with the availability of more powerful supercomputers. Operational forecasts are compared with “reforecasts” from |
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ISSN: | 0003-0007 1520-0477 |
DOI: | 10.1175/1520-0477(1998)079<2753:MOONWP>2.0.CO;2 |