ERA Data from the ECMWF
1. What is ERA ?
ERA is the computerised weather data from the European Centre for Medium-Range Weather Forecasts (http://www.ecmwf.int) by re-analysed and homogenised observation data, taken from scientific relevant observations worldwide. The first of three projects (ERA15) was followed by ERA40 (data 1957-09 to 2002-08) and ERA Interim (from 1979 on). Contracted by the German Meteorological Service (Deutscher Wetterdienst, DWD), the World Data Centre for Climate (WDCC) at DKRZ is the German distributor of these data.
2. Restrictions on ERA Data
At the beginning, ERA data has been open for scientific use to registered users only. This is the basis, on which WDCC disseminates the data. Since few years, ERA data may be used commercially as well (see ECMWF website).
See below for registration (Chapter 5: "How to get the data?").
The data are grouped in several ways:
by temporal resolution:
the assimilation of the observational data is done every couple of hours. ERA data is stored four times a (model) day. Additionally, monthly means of each of the four times separately are available, as well as the total monthly mean of all data of a certain parameter.
by spatial resolution:
for ERA40/Interim we only offer the spatial resolution of Gaussian Grid N80 (sometimes called "TL159") / N128 respectively. For atmospheric fields as model levels, the parameters 130, 135, 138, and 155 are offered on the corresponding spherical harmonic grid, which for ERA40/Interim is T159/N255.
The ECMWF also offers coarser ERA data (2 .5°) and data from their wave model.
by level type:
ground data have only the level "surface" (sfc), upper air fields can be retrieved for 60 different model levels or for 23 different pressure levels.
by forecast step:
forecasts have been calculated for 06,12, ... hours step width. Step width 00 corresponds to pure analysis, i.e., no forecast. At WDCC we offer the 00 and 06 hours step for ERA40. For ERA Interim the forecast steps 03,06,09 and 12 are available.
Step 00 contains intensive data (like temperature) - their values refer to the time given in the record header. In addition, forecast steps contain extensive data (like precipitation), which are accumulated from programme start (as given in the file header) over the step width.
by physical parameter:
the data is available for many physical parameters, mostly identified by their numbers as listed in table 128 at ECMWF (see link list below).
4. What ERA data is retrievable at DKRZ ?
Data is available in the CERA DB for three ERA projects:
- ERA-Interim: http://cera-www.dkrz.de/WDCC/ui/BrowseExperiments.jsp?proj=ERA_INTERIM
- ERA-40: http://cera-www.dkrz.de/WDCC/ui/BrowseExperiments.jsp?proj=ERA40
- ERA-15: http://cera-www.dkrz.de/WDCC/ui/BrowseExperiments.jsp?proj=ERA15
5. How to get the data ?
Find out, what types of data you need: start and end time, time resolution, forecast step, level (surface only, pressure levels, model levels) and physical parameters.
Fill in the "ecrana form" (found here) to confirm the agreement on data usage and fax to +49-40-460094-106 or send it to WDCC by surface mail.
Finally, apply for an ERA user account at data(at)dkrz.de.
6. Links to Further Information on ERA data
Links to more detailed information at ECMWF:
- ECMWF ERA product page
- ERA Project Reports
- ERA Project FAQs
- available ERA data
- ERA-Interim known issues
Coarser data is available from the Public Data Server of the ECMWF on a 2.5° x 2.5° grid.
7. Analysis of ERA data
Available software for data analysis are e.g. the Climate Data Operators (CDO).
For conversions between Gaussian grid and spectral representation use cdo commands: sp2gpl and gp2spl.
8. Further Information for Download
|ERA-40/ERA-Interim Data Usage and QC
ERA Report Series: Data Usage and Quality Control for ERA-40, ERA-Interim and the Operational ECMWF Data Assimilation System
An ERA40 Overview
|ERA-Interim Project (internal link: ERA-Interim Project)
Dee et al. (2011), The ERA-Interim reanalysis: configuration and performance of the data assimilation system. Q.J.R. Meteorol. Soc., 137: 553–597. doi: 10.1002/qj.828.
ERA40 Project Report: Project
ERA Report Series: The ERA-Interim Archive (version 2.0)
ERA40 Project Report: Archive
ERA40 Project Report: Numerics
On the following page you find some technical information on the ERA40 data.