Design of CMA S2S Data Archive Center and Key Technology

S2S, sub-seasonal to seasonal prediction project, is a WWRP/THORPEX-WCRP joint research project established to improve forecast skill and understanding on the sub-seasonal to seasonal time scale, and promote its uptake by operational centers and exploitation by the applications community. To achieve many of these goals, the establishment of an extensive data base of sub-seasonal (up to 60 days) forecasts and reforecasts (sometimes known as hindcasts) is advocated. Managing an extensive data base for the sub-seasonal time scale is a challenging task for the diverse characteristic of these forecasts (e.g., start dates, length of the forecasts, average periods, and updating frequency of forecasts).Open access to forecast data and user interface friendly data bases are important requirements for construction of S2S archiving data. CMA, one of two S2S data archive centers, is responsible for collecting S2S data from all data providers, performing basic quality check, archiving and storing data, and providing data service. The traditional FTP and a simple data downloading program based on ECMWF WebAPI is used to collecting data provided by all eleven S2S data centers. The data synchronization with another archive center of ECMWF is implemented by applying the combination strategies of common routine data transfer through FTP, ECMWF WebAPI based data download for missing reforecast data, and transferring missing real-time data copied from tapes directly by MARS system command. The file of compressed format TAR and GRIB2 is checked by executing command of tar and grib_get and its return value. A program based on the tigge_check command provided by GRIB_API is also developed to check the attribute of GRIB2 data, since all S2S data are saved as GRIB2 format. Through using GRIB_API command of grib_filter and designing a unified data form organized by a single center, a single date and a single meteorological parameter field, the unified S2S data are created to store in the online storage system which makes fast retrieval of data possible and open access. In the meantime, the unified form of S2S data file could be easily obtained their real storage addresses by their file names. The S2S data portal provides both free text and faceted search method to access forecast and reforecast data in the format of GRIB2 and NetCDF through online converting the data format.CMA S2S archive center is in operation since 15 November 2015. With the availability of data of all data providers, the construction of S2S archive center will be continued to improve the in-time of data integrity and data access methods.