Quality control, data base and gridded analysis products provided by the Global Precipitation Climatology Centre (GPCC) to serve the hydro-climatology community

Since its start in 1989 the Global Precipitation Climatology Centre (GPCC) performs global analyses of monthly precipitation for the earth's land-surface on the basis of in-situ measurements. Meanwhile, the data set has continuously grown both in temporal coverage (original start of the evaluation period was 1986), as well as extent and quality of the underlying data base. The high spatio-temporal variability of precipitation requires a high density of measurement data. The GPCC receives the SYNOP and CLIMAT messages in near real-time via the WMO GTS. Core data source of the GPCC analyses are the data from station networks operated by the National Meteorological/Hydrological Services worldwide; data deliveries have been received from ca. 190 countries. The GPCC integrates also other global precipitation data collections (i.e. FAO, CRU and GHCN), as well as regional data sets and has recently started collection and analysis of daily data while keeping its other activities upright. As a result of these efforts the GPCC holds the worldwide largest and most comprehensive collection of precipitation data, which is continuously updated and extended. The acquired data sets are pre-checked and imported into a relational data base, thus allowing a cross-comparison of data from the different sources. Any time new data sets are imported to the data base the metadata in the input data set are compared to those already available. Since the beginning of 2009 the precipitation data to be imported is compared against a background statistic. Exceptional values are checked and either confirmed, corrected or excluded from the analyses. Near-real-time products are the 'First Guess Product' (created for early detection, e.g., drought monitoring) and 'Monitoring Product' (created on WCRP request and for merging to satellite data), both with a spatial resolution of 1°x1°. Only an automatic quality control runs during the generation of the 'First Guess Product', whereas the data base is extended and a manual quality control is carried out for the 'Monitoring Product'. In addition the GPCC offers several non-real-time products based on additional data from national meteorological/hydrological services or other organizations. These are the 'Climatology' (based on ca. 64400 stations with climatological normals, focusing 1951-2000) and the 'Full Data Reanalysis' (currently version 5, time period 1901-2009), which is created for best spatial data coverage. 'VASClimO' is currently the homogenized product, which covers the period from 1951 till 2000. It will be replaced by the new product 'HOMPRA', which will extend the period from 1951 to 2005 and is scheduled to be delivered by end of 2011. Also in 2011 an analysis of daily precipitation is scheduled to start on basis of global SYNOP reports. This new 'First Guess Daily' will be released together with the 'First Guess Product' 3 to 5 days after the end of each month. To protect the interests of the data suppliers the GPCC is not providing the station related data, but all gridded products mentioned above are available free of charge at the GPCC web site (gpcc.dwd.de).