Malardel, S., N. Wedi, W. Deconinck, M. Diamantakis, C. Kuhnlein, G.
Mozdzynski, M. Hamrud, and P. Smolarkiewicz, 2015: A new grid for
the IFS. Newsletter No. 146 - Winter 2015/16, ECMWF, 6 pp., URL:
After many years of research and technical preparation, the
production of a new ECMWF climate reanalysis to replace ERA-Interim
is in progress. ERA5 is the fifth generation of ECMWF atmospheric
reanalyses of the global climate, which started with the FGGE
reanalyses produced in the 1980s, followed by ERA-15, ERA-40 and
most recently ERA-Interim. ERA5 will cover the period January 1950
to near real time.
ERA5 is produced using high-resolution forecasts (HRES) at 31
kilometer resolution (one fourth the spatial resolution of the
operational model) and a 62 kilometer resolution ten member 4D-Var
ensemble of data assimilation (EDA) in CY41r2 of ECMWF's Integrated
Forecast System (IFS) with 137 hybrid sigma-pressure (model) levels
in the vertical, up to a top level of 0.01 hPa. Atmospheric data on
these levels are interpolated to 37 pressure levels (the same levels
as in ERA-Interim). Surface or single level data are also available,
containing 2D parameters such as precipitation, 2 meter temperature,
top of atmosphere radiation and vertical integrals over the entire
atmosphere. The IFS is coupled to a soil model, the parameters of
which are also designated as surface parameters, and an ocean wave
model. Generally, the data is available at an hourly frequency and
consists of analyses and short (12 hour) forecasts, initialized
twice daily from analyses at 06 and 18 UTC. Most analyses parameters
are also available from the forecasts. There are a number of
forecast parameters, e.g. mean rates and accumulations, that are not
available from the analyses.
Improvements to ERA5, compared to ERA-Interim, include use of
HadISST.2, reprocessed ECMWF climate data records (CDR), and
implementation of RTTOV11 radiative transfer. Variational bias
corrections have not only been applied to satellite radiances, but
also ozone retrievals, aircraft observations, surface pressure, and
Please note: DECS is producing a CF 1.6 compliant netCDF-4/HDF5
version of ERA5 for the CISL RDA at NCAR. The netCDF-4/HDF5 version
is the de facto RDA ERA5 online data format. The GRIB1 data format
is only available via NCAR's High Performance Storage System (HPSS).
There is a one-to-one correspondence between the netCDF-4/HDF5 and
GRIB1 files, with as much GRIB1 metadata as possible incorporated
into the attributes of the netCDF-4/HDF5 counterpart.