Observations, assimilation and the improvement of global weather prediction – some results from operational forecasting and ERA-40

doi:10.1017/CBO9780511617652.017

Chapter 16 - Observations, assimilation and the improvement of global weather prediction – some results from operational forecasting and ERA-40

Published online by Cambridge University Press: 03 December 2009

Adrian J. Simmons

Edited by

Tim Palmer and

Renate Hagedorn

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Adrian J. Simmons: Affiliation:
European Centre for Medium-Range Weather Forecasts, Reading
Tim Palmer: Affiliation:
European Centre for Medium-Range Weather Forecasts
Renate Hagedorn: Affiliation:
European Centre for Medium-Range Weather Forecasts

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Summary

Basic aspects of the atmospheric observing system and atmospheric data assimilation are summarised. Characteristics of the assimilation of observational data from the late 1950s onwards in the ERA-40 reanalysis project, and of medium-range forecasts run from the ERA-40 analyses, are used to illustrate improvement in the observing system and to place in context the improvement of the operational forecasts of the European Centre for Medium-Range Weather Forecasts (ECMWF) over the past 25 years. Recent advances in operational forecasting are discussed further. It is shown that the analyses of two centres, ECMWF and the Met Office, have converged substantially, but that there remain nevertheless significant differences between these analyses, and between the forecasts made from them. These differences are used to illustrate several aspects of data assimilation and predictability. Inferences from differences between successive daily forecasts and from spectra of forecast errors are also discussed for the ECMWF system.

Introduction

This chapter is based on the introductory lecture given to the Annual ECMWF Seminar for 2003, which was devoted to data assimilation. The subject had last been addressed in the Seminar Series in 1996. In the opening lecture on that occasion, the late Roger Daley discussed how, over the preceding 15 years, data assimilation had evolved from being a minor and often neglected subdiscipline of numerical weather prediction to become not only a key component of operational weather forecasting but also an approach that was important for environmental monitoring and estimation of the ocean state.

Type: Chapter
Information: Predictability of Weather and Climate , pp. 428 - 458

DOI: https://doi.org/10.1017/CBO9780511617652.017 [Opens in a new window]

Publisher: Cambridge University Press

Print publication year: 2006

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