The ECMWF ERA-15 Re-Analysis Project
Introduction
The European Centre for Medium-Range Weather Forecasts
(ECMWF) has provided global atmospheric analyses from its archive
for many years. The ERA-15 Re-analysis project was devised in response to wishes
expressed by many users for a data set generated by a modern,
consistent, and invariant data assimilation system. A more detailed description of the ERA-15 project
can be downloaded here in .pdf format.
Associated Organisations
ERA has received assistance from the ECMWF Council, the European
Community, the University of California, the Japan Meteorological
Agency (JMA), Cray Research Incorporated, and the Center for Ocean-Land-Atmosphere
Studies (COLA). In addition, data and co-operation have been forthcoming
from many quarters, including ECMWF Member States, the University
of Innsbruck, the National Ocean and Atmospheric Administration
(NOAA) and National Center for Atmospheric Research (NCAR) in
the United States of America, and the Australian Bureau of Meteorology
(BoM).
Data Sources
The ERA-15 Re-analysis project incorporated a number of observation sources.
The real time World Meteorological Organisation (WMO) World Weather Watch data from the ECMWF
archive (which had a 3 day cut-off) is augmented by the following
additional data:
- NOAA satellite radiance data for the 15-year period.
- The Comprehensive Ocean-Atmosphere Data Set (COADS) ship
data.
- The First GARP Global Experiment (FGGE) and the Alpine Experiment (ALPEX) data.
- GMS cloud winds, AIREP and TEMP data supplied by the JMA.
- Pseudo-observations data from BoM.
Sea surface temperature analyses for ERA-15 are provided by the
United Kingdom Meteorological Office (UKMO) for the early period, and
by NOAA from November 1981 onwards. Sea ice cover has been derived
from SMMR and SSM/I satellite data. For a comprehensive report of the data sources
used in the ERA-15 project you can download the
ERA-15 Project Report.
The ERA-15 Data Assimilation System
The ERA-15 data assimilation system is a special version of the
ECMWF Operational data assimilation system which incorporates:
- Intermittent statistical (Optimum Interpolation) analysis
with 6-hour cycling.
- One dimensional variational (1D-VAR) physical retrieval of
TOVS (Tiros Operational Vertical Sounder) cloud cleared radiance (CCR) data.
- Diabatic, non-linear normal mode initialisation (five vertical
modes).
- A spectral T106 forecast model with 31 hybrid vertical model levels,
and a fully three-dimensional semi-Lagrangian advection scheme.
- A physical parametrization package including:
- mean orography with a compatible parametrization of sub-grid
scale orography;
- a four layer prognostic soil scheme with no external forcing;
- an interactive cloud/radiation scheme with full model representation
of cloud water content and cloud cover;
- a planetary boundary layer parametrization based on similarity.
For a more detailed description of the ERA-15 data assimilation system
please see the
ERA-15 Project Report.
The ECMWF Global Atmospheric Model
The ECMWF Global Atmospheric Model used to generate the ERA-15 dataset was consistent with the
model used for Operational Analyses in the early 1990s. The ERA-15 model run was started in
February 1993 and was completed in 1996.
For a more detailed description of the ERA-15 model please download the
ERA-15 Project Report.
Validation and Evaluation of the ERA-15 dataset
Much research has been performed using the ERA-15 dataset including comparisons and
evaluations of the product itself. For a detailed description of ERA-15 documented by the
ECMWF see the
ERA-15 Project Report Series.