From short-range barotropic modelling to extended-range global weather prediction: a 40-year perspective

Abstract

At the end of the 20th century, we can look back on a spectacular development of numericalweather prediction, which has, practically uninterrupted, been going on since the middle of thecentury. High-resolution predictions for more than a week ahead for any part of the globe arenow routinely produced and anyone with an Internet connection can access many of theseforecasts for anywhere in the world. Extended predictions for several seasons ahead are alsobeing done–the latest El Ninño event in 1997/1998 is an example of such a successful prediction.The great achievement is due to a number of factors including the progress in computationaltechnology and the establishment of global observing systems, combined with a systematicresearch program with an overall strategy towards building comprehensive prediction systemsfor climate and weather. In this article, I will discuss the different evolutionary steps in thisdevelopment and the way new scientific ideas have contributed to efficiently explore the computingpower and in using observations from new types of observing systems. Weather predictionis not an exact science due to unavoidable errors in initial data and in the models. To quantifythe reliability of a forecast is therefore essential and probably more so the longer the forecastsare. Ensemble prediction is thus a new and important concept in weather and climate prediction,which I believe will become a routine aspect of weather prediction in the future. The limitbetween weather and climate prediction is becoming more and more diffuse and in the finalpart of this article I will outline the way I think development may proceed in the future.