wiki:udg/ecoms/dataserver

Version 1 (modified by gutierjm, 9 years ago) (diff)

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The SPECS-EUPORIAS Data Portal is based on a password-protected THREDDS data server (TDS) providing metadata and data access to a set of georeferenced atmospheric variables using OPeNDAP and other remote data access protocols. The variables names, units and additional metadata follow the CF convention. The variables are spatial grids based on multidimensional arrays of indexed values, following Unidata's _Coordinate convention12.

Typically the data portal will include information at a daily resolution, but monthly-aggregated values could be also provided in some cases due to data limitations (in particular, Mètèo-France and Met Office have agreeed to provide monthly mean hindcasts for their use by the SPECS and EUPORIAS partners). In general, the data available will be typical surface variables (e.g. precipitation and near-surface temperature), although several variables (e.g. geopotential and temperature) on pressure levels will also be stored for the statistical downscaling activities.

The data gathering activities have initially focused on the ECMWF System4 seasonal model. The Meteorological Archival and Retrieval System (MARS) is the main repository of meteorological data at the ECMWF (European Centre for Medium-Range Weather Forecasts). It contains terabytes of operational and research data as well as data from special projects3. The large amount of information stored and the inherent complexities of data access, download and post-processing is a first shortcoming for a flexible use of these datasets by a large number of partners. To overcome this issue, a reduced subset of surface variables4 (precipitation, temperatures and mean sea level pressure) have been downloaded from MARS (a colection of GRIB-1 files) at 0.75º spatial resolution and made available throught the SPECS-EUPORIAS data portal. The downloaded data has been exposed as three different virtual datasets using TDS:

  • System4 seasonal range (15 members): There are twelve initializations (hereafter called runtimes) per year (the first of January, February, ...) running for 7 months (hereafter called simply times). An ensemble of 15 members is available for the whole 1981-2010 period.
  • System4 seasonal range (51 members): There are only four runtimes per year (the first of February, May, August and November) and the forecasts run for 7 months. An ensemble of 51 members is available for the whole 1981-2010 period.
  • System4 annual range (15 members): As in the previous case, there are four runtimes per year, but the forecasts run for 13 months. An ensemble of 15 members is available for the whole 1981-2010 period.

Data gathering activities will next move to the CFS (http://cfs.ncep.noaa.gov) version 2 hindcast, developed at the Environmental Modeling Center at NCEP and also to reanalysis and observational datasets.