Climate Monitoring of Precipitation: The GPCC - Status and plans

1. Meeting of CCl-Expert Team on „Climate Monitoring incl. the use of Satellite and Marine Data and Products“, 27-29 October 2009, Offenbach, Germany Climate Monitoring of Precipitation: The GPCC - Status and plans U. Schneider, A. Meyer-Christoffer, B. Rudolf Global Precipitation Climatology Centre Deutscher Wetterdienst Department Hydrometeorology

2. Climate Monitoring of Precipitation: The GPCC - Status and plans Outline • Background and international integration • Different user requirements • Data base and data sources available (near- and non-realtime) • GPCC‘s current precipitation analysis products • Near real-time analyses • Non real-time analyses • Outlook (New analysis products)

3. Background • The GPCC was established by end of 1988 at Deutscher Wetterdienst (DWD) on invitation by WMO, and it is the component for the analysis of in-situ measurements of the Global Precipitation Climatology Project(GPCP) GPCC’s monitoring and analysis of global land-surface precipitation based on in-situ observations is comprising the major functions: • Collection of near real-time precipitation data available via GTS • Acquisition of additional data from NMHSs and research projects • Integration of historical data sets (such as CRU, FAO, GHCN) • Quality-control of precipitation data and station meta data, • error assessment and correction • Production of gridded data sets using objective analysis methods

4. International integration • Besides its function in GPCP the GPCCcontributes also to GCOSand GTN-H (Global Terrestrial Network for Hydrology) Since Jan. 2004 the GPCC has taken over the operation of the GCOS Surface Network-Monitoring Centre(GSNMC)for precipitation In Dec. 2006 the GPCC started its newest function as a WMO CBS Lead Center for GCOS data for Europe

5. User requirements The features of gridded precipitation data as required by the users: • Timeliness (for drought monitoring) • High resolution(for regional structures in global maps) • High accuracy(for verification of model results) • Homogeneity(for climate change and variability analysis) All of these requirements cannot be met by one single gridded data set ==> Special products have been designed and optimized with respect to the priorities as given by the application purpose

6. GPCC data sources • Near real-time: • GTS SYNOP (DWD RTH Offenbach) • GTS CLIMAT (DWD RTH Offenbach) • GTS CLIMAT (JMA RTH Tokyo) • GTS CLIMAT (UKMO RTH Exeter) • SYNOP-based (NOAA RTH Washington) • Non real-time: • Additional data from ca. 185 countries • International project data (GEWEX-related and other) • Historical data collections (CRU, FAO, GHCN)

7. Near real-time GTS data base

8. Near real-timeprecipitation products GPCC is providing the following gridded data sets on a quasi-operational basis (GTS data base): • A First Guess of Monthly Precipitation Anomaliesavailable within 5 days after the end of the month via internet, used for drought monitoring (e.g. byFAO). • The Precipitation Monitoring Product available within 2 months, • used by GEWEX/GPCP as early in-situ reference.

9. GPCC‘s First Guess of precipitation anomalies • Availability: • period Oct. 2003 to Aug. 2009 • within 5 days after the end of the month • Data base: • monthly precipitation totals accumulated from SYNOP reports • received via GTS at DWD, Offenbach a.M. (ca. 6,000 stations) Automatic-only QC ofSYNOP reports in the calculation of monthly precipitation totals (check of large precipitation amounts against the weather information, consistency check of reports overlapping in time, etc.) Monthly precipitation totals are calculated only if temporal coverage by SYNOP reports in the month is at least 70%

10. GPCC First Guess for Europe, August 2005 Precipitation anomaly for August 2005 • France and Iberian Peninsula are still dryer than normal • while Switzerland, southern Germany and the Balkans faced severe floods

11. GPCC‘s Precipitation Monitoring Product • Availability: • period Jan. 1986 up to Dec. 2006 (V.1) • period Jan. 2007 up toJune 2009(V.2) • within 2 months after the end of the month • Data base (monthly precipitation totals, ca. 7,500 stations): • accumulated fromSYNOP reports received via GTS at DWD, • Offenbach a.M. • accumulated fromSYNOP reports received via GTS at NOAA, • Washington D.C. • received in CLIMAT reports via GTS at DWD, Offenbach, UKMO, Exeter and JMA, Tokyo GPCC‘s Monitoring Product V.2 is the in-situ componentof the combined GPCP-V2.1 data set

12. GPCC data base for different products 1986: Original start of evaluation period Drop: Time delay of data provided Sept. 2008 Feb. 2005

13. Non real-timeprecipitation products From time to time (after significant enlargements of the data base) reanalyes of the following gridded products are being generated: • The Full Data Reanalysis(Version 4), • optimized for high spatial resolution and accuracy, • used for model verification and hydrological studies. • The VASClimO Analysis (Version 1.1), • optimized for time-series homogeneity and quality, • suited for studies on climate variability and trends.

14. GPCC‘s Full Data Reanalysis V.4 Full DataProduct (Version 4, Sept. 2008) optimized for high spatial resolution and accuracy designedfor model verification and hydrological studies • Availability: • periodJan. 1901 up to Dec. 2007 • on a 2.5°-, 1°- and 0.5°-grid • Data base: • ca. 10,000-45,000 stationsper month (overall ca. 50,650 stations) • including additional national/regional data collections from NMHSs and research projects of 180 countries; • global data collections of CRU, FAO, GHCN

15. GPCC‘s new precipitation climatology: January

16. GPCC‘s new precipitation climatology: July

17. 50-year Analysis (VASClimO) V1.1 VASClimO 50-year Analysis (Version 1.1, Feb. 2005) optimized for time-series homogeneity and quality, suited for studies on climate variability and trends • Availability: • periodJan. 1951 up to Dec. 2000 • on a 2.5°-, 1°- and 0.5°-grid • Data base: • ca. 9,400 stations with an almost complete coverage (>= 90%) • over the period • homogeneity tests applied / data homogenized • outliers detected and eliminated Analysis of relative anomalies at the stations superimposed on background climatology of 28,000 stations

18. Additional analysis products of the GPCC • Since Jan. 2007 the following products are operationally available: • weather-dependentcorrection of the systematic gauge- • measuring error for the month, • discrimination of different precipitation types (liquid, solid, mixed)

19. Outlook Significant enlargement of GPCC‘s data base Further improvements of data base quality ==> Update of GPCC product suite

20. Current GPCC data base for different products 1986: Original start of evaluation period Drop: Time delay of data provided

21. Current GPCC data base for different products

22. GPCC data base (according to data sources)

23. GPCC Climatological data base Database for GPCC climatology:2008 Near real-time and non real-time data Monthly in-situ precipitation stations used currently at GPCC as basis for anomaly analyses (Number of stations: 50,650)

24. GPCC Climatological data base Database for GPCC climatology: 2009 Monthly in-situ precipitation stations used in future at GPCC as basis for anomaly analyses (Number of stations: ca. 58,500)

25. Outlook Planned new analysis products of the GPCC (in Dec. 2009-Feb. 2010): • New Global Precip. Climatology (ca. 58,500 stations) • Monitoring Product (Version 3, since Jan. 2007) • Full Data Reanalysis (Version 5, 1901-2007) • VASClimO Analysis (Version 2, 1951-2005) After vacant position in GPCC will be refilled by April 2010 analysis of daily precipitation will be restarted

26. Access to GPCC‘s Precipitation Products http://gpcc.dwd.de

27. Additional material

28. GPCC‘s Precipitation Monitoring Product Monthly precipitation data from CLIMAT reports can serve as high-quality reference data, but only after thorough QC • Problems with monthly precipitation data from CLIMAT reports: • typical typing / coding errors - 1/10 mm instead of mm - 999X mm instead of X/10 mm (--> 1 mm) Monthly precip. totals accumulated from SYNOP reports often have an incomplete coverage of the month resulting in uncertainties The monthly precipitation data of all 3 GTS sources undergo an automatic pre-control, whereby the best of the different GTS data sources is selected, andan additional manual QC of the data flagged as questionable

29. The sampling error as function of network density and variability The sampling error of area-mean precipitation calculated from point-data depends on the number of stations and the regional variabilty of the parameter. The required network densitydepends on temporal and spatial resolution considered and desired accuracy of the product: 10% error on a 2.5° grid requires 40,000 stations! (Fig. GPCC after WMO-No. 115, 1985)

30. Difference of correction (%) for Jan. 2005 Climatological - New method Temperature anomalies for Jan. 2005 (from normals 1961-1990) New method for correction of systematic gauge measuring error Large-scale coherent structures in the difference field of the correction between climatological approach and new method correspond to temperature anomalies

31. July 2005 New method for correction of systematic gauge measuring error Fraction of solid precipitation (%) Jan. 2005