Evaluation of the Ozone and Water Vapour Datasets of the 40-Year European Re-analysis of the Global Atmosphere Upper Troposphere Lower Stratosphere (UTLS) Round 2 project led by Prof. A. O Neill, Dr W. Lahoz and Prof. B. Hoskins, Centre for Global Atmospheric Modelling, Department of Meteorology, University of Reading.

Re-analyses datasets, such as the 40-year re-analysis dataset (ERA-40), have been produced by the European Centre for Medium Range Weather Forecasts. This has provided an invaluable tool for a wide range of modelling, theoretical and observational studies of the atmosphere, including the UTLS region. This was because they have the advantage of being global, self-consistent and relatively long-term. It was vital that the ERA-40 dataset was carefully evaluated before projects studying the UTLS region, for example, draw conclusions based on its use.

This project undertook an evaluation of the ERA-40 dataset by comparing ozone and water vapour fields (important for climate, radiation and dynamics) in the UTLS region using independent satellite data from the Upper Atmosphere Research Satellite (UARS), aircraft data from the Measurements of Ozone by Airbus In Service Aircraft (MOZAIC) programme, measurements from fields campaigns (e.g. the European Arctic Stratospheric Experiment (EASOE), and the Second European Stratospheric Arctic and Mid-latitude Experiment (SESAME).

The objectives of the UTLS-Ozone ERA40 Validation project were:

To evaluate the ozone and water vapour datasets in ERA-40, including the identification of shortcomings and suggestions for improvements.

To gain intimate knowledge of the data quality and shortcomings of ERA-40 datasets other than ozone and water vapour, via membership of the ERA-40 data evaluation team.

To provide users with quality-controlled, three dimensional ozone and water vapour datasets from the ERA-40 analyses, together with error statistics on the reliability of the fields.

To provide support for measurement campaigns associated with the study of chemistry/ climate interactions.

To provide support to the scientific community in the form of climatologies for studies of atmospheric variability and predictability.

To provide interdisciplinary training in data evaluation and analysis techniques, earth observation sciences and atmospheric modelling.