ERA-15 Project

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1. Introduction

The ECMWF Re-analyses (ERA) project objective was to produce a new, validated 15 year data set of assimilated data for the period 1979 to 1993. During the years of ECMWF's Operational activities the archive of products has been used extensively by researchers all over the world. This archive, in recent years, has supported the ECMWF TOGA (Tropical Ocean Global Atmosphere) data set, providing the global atmospheric data used in much of TOGA research.

The Operational data, while providing a valuable resource for such work, is affected by the major changes in models, analyses technique, assimilation, and data usage which are essential to the evolution of continuously improving forecast systems. They also can make use only of those data which become available within near real time. Bengtsson and Shukla expressed the idea that such considerations provide valid reasons for performing a consistent re-analyses of atmospheric data as early as 1988. Typical research applications which could make good use of re-analyses include general circulation diagnostics, atmospheric low-frequency variability, the global hydrological and energy cycle, studies of predictability, coupled ocean-atmosphere modelling, and observing system performance.

ERA only became a practical reality through the funding and assistance received from many quarters, including the ECMWF Council, the European Union, the University of California (PCMDI), the Japan Meteorological Agency (JMA), the World Climate Research Programme (WCRP) of the World Meteorological Organisation (WMO), the Centre for Ocean-Land-Atmosphere Studies (COLA), the National Center for Atmospheric Research (NCAR), the National Centers for Environmental Prediction (NCEP) and Cray Research Incorporated.

David Burridge is the Project Chairman. The project team is Rex Gibson (Project Manager), Per Kållberg, and Sakari Uppala. This team was augmented by Atsushi Nomura from JMA (March 1993 to March 1995), and by two European Union Fellowship Students, Angeles Hernandez (November 1993 to December 1995), and Encarna Serrano Mendoza (January 1994 to April 1996).

In the planning and development phase a Steering Group advised on matters of scientific and policy importance, and additional advice was obtained by setting up an External Advisory Group, comprised of eminent scientists from Europe and the United States of America.

The project began in February 1993. The first phase of the work required the acquisition and preparation of the observations and forcing fields, experimentation to determine the composition of the production system, and the development of both the production system and the internal validation tools. The final production system was adopted in 1994, and there followed a period of sustained production, monitoring and validation throughout 1995 and the first nine months of 1996.

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