ASCOS ERA-Interim Products Description
Please contact Gijs de Boer (e-mail, phone: +1 303-497-6648) with questions regarding these files. These files are published to the ASCOS site with the permission of ECMWF.
There are two files included:
ascos_ERAInt.nc are the ERA-Interim pressure level and surface analysis files interpolated to the Oden's position.
Ascos_ERAInt_other.nc are the ERA-Interim model forecast files interpolated to the Oden's position.
All interpolations are linear. Please note that several of the variables within the forecast files are not instantaneous values, but rather are accumulated over the simulation period.
ERA-Interim Description:
ERA-Interim represents a major undertaking by ECMWF (European Centre for Medium-Range Weather Forecasts) to produce a reanalysis with an improved atmospheric model and assimilation system which replaces those used in ERA-40, particularly for the data-rich 1990's and 2000's, and to be continued as an ECMWF Climate Data Assimilation System (ECDAS) until superseded by a new extended reanalysis. Preliminary runs indicated that several of the inaccuracies exhibited by ERA-40 such as too-strong precipitation over oceans from the early 1990's onwards and a too-strong Brewer-Dobson circulation in the stratosphere, were eliminated or significantly reduced. Production of ERA-Interim, from 1989 onwards, began in summer of 2006. (The period 1979-1988 was prepended in 2011.)
Through systematic increases of computing power, 4-dimensional variational assimilation (4D-Var) became feasible and part of ECMWF operations since 1997, paving the way to base ERA-Interim on 4D-Var (rather than 3D-Var as in ERA-40). Enhanced computing power also allowed horizontal resolution to be increased from T159 (N80, nominally 1.125 degrees for ERA-40) to T255 (N128, nominally 0.703125 degrees), and the latest cycle of the atmospheric model (IFS Cy31r1/2) to be used, taking advantage of improved model physics. ERA-interim retains the same 60 model levels used for ERA-40 with the highest level being 0.1 hPa. In addition, data assimilation of ERA-Interim also benefits from quality control that draws on experience from ERA-40 and JRA-25, variational bias correction of satellite radiance data, and more extensive use of radiances with an improved fast radiative transfer model.
ERA-Interim uses sets of observations and boundary forcing fields acquired for ERA-40 through 2001, and from ECMWF operations thereafter. Noteworthy exceptions include new ERS (European Remote Sensing Satellite) altimeter wave heights, EUMETSAT (European Organisation for the Exploitation of Meteorological Satellites) reprocessed winds and clear-sky radiances, GOME (Global Ozone Monitoring Experiment) ozone data from the Rutherford Appleton Laboratory, and CHAMP (CHAllenging Minisatellite Payload), GRACE (Gravity Recovery and Climate Experiment), and COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) GPS radio occultation measurements processed and archived by UCAR (University Corporation for Atmospheric Research).
NCAR's Data Support Section (DSS) is performing and supplying a grid transformed version of ERA-Interim, in which variables originally represented as spectral coefficients or archived on a reduced Gaussian grid are transformed to a regular 512x256 N128 Gaussian grid. In addition, DSS is also computing horizontal winds (u,v) from spectral vorticity and divergence where these are available. Processing of analysis groups and the surface forecast has been completed for January 1979 through August 2011 (inclusive), and will continue as ERA-Interim becomes available thereafter (please refer to the 'Period details by subset' tab immediately below for the time range currently available for each group). Data is currently available via NCAR's High Performance Storage System (HPSS), or by delayed mode request which transfers files from the HPSS to our web server for internet download, or via direct internet download.
Original files were created by ECMWF under the ERA-Interim project. The data for this study were downloaded from the Research Data Archive (RDA) which is maintained by the Computational and Information Systems Laboratory (CISL) at the National Center for Atmospheric Research (NCAR). NCAR is sponsored by the National Science Foundation (NSF). The original data are available from the RDA in dataset number ds627.0.
References:
Berrisford, P., P. Kallberg, S. Kobayashi, D. Dee, S. Uppala, A.J. Simmons, P. Poli, and H. Sato, 2011: Atmospheric conservation properties in ERA-Interim. Quart. J. R. Meteorol. Soc., 137, 1381-1399 (DOI: 10.1002/qj.864).
Dee, D.P., with 35 co-authors., 2011: The ERA-Interim reanalysis: configuration and performance of the data assimilation system. Quart. J. R. Meteorol. Soc., 137, 553-597 (DOI: 10.1002/qj.828).
Poli, P., S.B. Healy, and D.P. Dee, 2010: Assimilation of Global Positioning System Radio Occultation data in the ECMWF ERA-Interim reanalysis. Quart. J. R. Meteorol. Soc., 136, 1972-1990 (DOI: 10.1002/qj.722).
Simmons, A.J., K.M. Willett, P.D. Jones, P.W. Thorne, and D.P. Dee, 2010: Low-frequency variations in surface atmospheric humidity, temperature and precipitation: Inferences from reanalyses and monthly gridded observational datasets. J. Geophys. Res., 115, 1-21 (DOI: 10.1029/2009JD012442).
Dee, D.P., and S. Uppala, 2009: Variational bias correction of satellite radiance data in the ERA-Interim reanalysis. Quart. J. R. Meteorol. Soc., 135, 1830-1841 (DOI: 10.1002/qj.493).
Kobayashi, S., M. Matricardi, D.P. Dee, and S. Uppala, 2009: Toward a consistent reanalysis of the upper stratosphere based on radiance measurements from SSU and AMSU-A. Quart. J. R. Meteorol. Soc., 135, 2086-2099 (DOI: 10.1002/qj.514).
Simmons, A, S. Uppala, D. Dee, and S. Kobayashi, 2007: ERA-Interim: New ECMWF reanalysis products from 1989 onwards. Newsletter 110 - Winter 2006/07, ECMWF, 11 pp.