The Global Precipitation Climatology Centre (GPCC) Serving the Hydro-Climatology Community

The Global Precipitation Climatology Centre (GPCC) Serving the Hydro-Climatology Community Bruno Rudolf, Andreas Becker, Udo Schneider, Anja Meyer-Christoffer, Markus Ziese, Peter Finger Deutscher Wetterdienst t Department of Hydrometeorology Global Precipitation Climatology Centre 1

Outline GPCC Background and functions of the Global Precipitation Climatology Centre (GPCC) GPCC data base and provenance Methods in use for QC and gridding GPCC Products Sampling error vs. high-resolution products and trend analysis Frequencies of extreme events Outlook Global Precipitation Climatology Centre 2

The Global Precipitation Climatology Centre (GPCC) Established by the World Meteorological Organization WMO in the year 1988 undertaken by Deutscher Wetterdienst DWD contributes to the Global Climate Observing System GCOS and the World Climate Research Programme WCRP thousands of users world-wide scientific task: quantitative assessment of global precipitation p and investigation of the global water cycle Global Precipitation Climatology Centre 4

The functions of the GPCC collection of observed precipitation data world-wide data processing, quality control, storage data analysis, production of gridded data fields distribution of the gridded data fields contribution to international programs Global Precipitation Climatology Centre 5

data sources Near real-time regularly exchanged data via the WMO Global Main Telecommunication Network hourly/daily weather reports (SYNOP) ca. 6,500 stations monthly yclimatological atoogca totas(c totals (CLIMAT) ca. 2,300 stations ca. 8,000 stations Non real-time: Additional data received from ca. 190 countries plus: Historical data collections (CRU, FAO, GHCN) International project data (GEWEX and other) totally more than 64,000 stations Global Precipitation Climatology Centre 7

data base Data coverage by country Global Precipitation Climatology Centre 8

data base More More than than 64,000 64,000 stations stations providing climatic normal means means status status 2010/10 Data used as climatologic background for GPCC gridded data sets Global Precipitation Climatology Centre 9

quality control Separate storage of the data from different sources The source specific storage of the data serves an important basis for quality control as well as for understanding, traceability and later re-production Global Precipitation Climatology Centre 11

quality control Quality-control with 4 levels: 1a: Pre-control of SYNOPs 1b: Pre-control of CLIMATs 1c: Format-check of individual data sets 2: Overall visual control of individual data sets 3: Check of station meta data during the loading process 4: Semi-automatic QC of monthly precipitation data: Statistical pre-control and visual check of questionables Global Precipitation Climatology Centre 12

gridding Gridding of the station data for individual months Long term mean monthly precipitation normals Monthly precipitation anomaly gridded from station anomalies Gridded monthly precipitation totals Global Precipitation Climatology Centre 13

products GPCC near real-time products Routinely produced gridded data sets available within: application: number of stations: 5 days First Guess Anomalies drought monitoring FAO ~ 6,500 2 months Monitoring Product WCRP/GEWEX early reference ~ 7,500 Additional information provided for monitoring product Number of stations per grid box Sampling error Stochastic error Systematic error assessment This information is updated every month Global Precipitation Climatology Centre 15

products Schedule for the release of new products Global Precipitation Mean Climatology -period 1951-2000 - based on about 64,000 stations Nov 2010 Full Data Reanalysis Version 5 - period 1901-2009 - based on all available data (64,000 stations) ti Nov 2010 Trend analysis for selected data time-series - period 1951-2005 - based on complete data time-series (~ 16,000 stations) early 2011 publication of the methods used and results to be submitted early 2011 Global Precipitation Climatology Centre 16

data base Temporal data coverage Full Data Product Version 4 and Version 5 Global Precipitation Climatology Centre 17

GPCC Product examples: a) a) First Guess Analysis for August July 2010 2010 (total (total & anomaly) Global total patterns typical for La Nina season Anomalies across Indian sub-continent contain precipitation causing Pakistan flooding Global Precipitation Climatology Centre 18

GPCC Product examples: b) Monitoring (top row) and (c) Full Data Product El Nino Winter 1997/98 Please note the excellent overall quality of the monitoring product available 2 months after the fact, but also the improvement in the Full Data Product across central Africa! Global Precipitation Climatology Centre 19

sampling error Monthly precipitation Statistical error < 10% 16 stations per grid required Daily precipitation Statistical error < 20% 40 stations per grid required!! Figure: GPCC after Jenne and Joseph, WMO-No. 115, 1985 Global Precipitation Climatology Centre 21

station density Monthly precipitation error < 10% 16 stations per grid, i.e. approximately 40 000 stations required globally GPCC Climatology 1951-2000: Number of stations per 1º grid cell Areas in dark green and blue = Sufficient station density Global Precipitation Climatology Centre 22

station density Daily precipitation error < 20% GPCC, Monitoring Product, Sep 2009: No. of stations per 2,5º grid cell Areas in blue = Sufficient station density 40 stations per grid required!! i.e. approximately 100 000 stations required globally!! Global Precipitation Climatology Centre 23

Daily data analysis -0.40-0.31-0.04 Linear trend (slope) for number of days with - 004 0.04 daily precipitation of 30 mm/d or more -0.17-0.24 period 1931-2008 -0.55-0.18 078 decrease - 0.78-0.18 area size ca. 50x50 km2 200-400 msl Global Precipitation Climatology Centre 24

Daily data analysis +055 0.55 + 0.92 + 0.15 + 0.36 + 0.30 + 0.34 + 0.52 + 0.26 + 0. 73 Linear trend (slope) for number of days with +007 0.07 +105 1.05 daily precipitation of + 1.37 30 mm/d or more + 1.62 period 1931-2008 + 0.33 + 2.03 + 0.95 +155 1.55 + 0.80 + 0.46 +086 0.86 + 0.46 increase area size + 0.29 + 0.65 +017 0.17 ca. 50x50 km2 + 0.45 200-400 msl Global Precipitation Climatology Centre 25

Daily data analysis +055 0.55-0.40-0.04 + 0.92 + 0.15-0.31-004 0.04 + 0.36 + 0.30 + 0.34-0.17 + 0.26 + 0. 73 Linear trend (slope) for number of days with +007 0.07 +105 1.05 daily precipitation of + 0.52-0.55 + 2.03 + 0.33 + 0.95-0.18 + 0.46 + 0.46-078 0.78 + 1.37 30 mm/d or more + 1.62 period 1931-2008 -0.24 +155 1.55 + 0.80 +086 0.86 all 37 stations increase area size + 0.29 + 0.65 +017 0.17 decrease ca. 50x50 km2 + 0.45 200-400 msl -0.18 Global Precipitation Climatology Centre 26

1955-1964 1965-1974 1975-1984 1985-1994 1995-2004 S U M M E R Number of days with heavy rain (i.e. days with totals exceeding 60 mm) for decades W I N T E R Global Precipitation Climatology Centre 28

1955-1964 1965-1974 1975-1984 1985-1994 1995-2004 S U M M E R Number of dry days (i.e. days with totals less than 1 mm) for decades W I N T E R Global Precipitation Climatology Centre 29

Further Outlook: GPCC Climatology 2010 and Full Data Product Version 5 (almost done) Peer-reviewed publication on GPCC data base (ASAP) Upload to IPCC portal Contribution to IPCC (Q1 2011) Selection of homogeneous time series for assembling a new homogenized precipitation re-analysis (HOMPRA) (Year 2011) Commence near real-time daily SYNOP-based Products (Year 2011) Extend daily analysis to re-analysis of historical data (from 2011 ongoing) Global Precipitation Climatology Centre 31

Web site Access to GPCC s Precipitation Products http://gpcc.dwd.de Email: gpcc@dwd.de Global Precipitation Climatology Centre 32

GPCC staff members: Dr. Andreas Becker (scientist, head of GPCC) Udo Schneider (scientist) Anja Meyer-Christoffer (scientist) Markus Ziese (scientist, new member) Peter Finger (programmer) Peter Stender (technician) i Astrid Heller (technician) Jan Niclas Breidenbach (technician) Dr. Bruno Rudolf (supervisor, dir. dept. hydrometeorology) Global Precipitation Climatology Centre 33

Additional Material: Global Precipitation Climatology Centre 34

data bas The data base Jan 1901 Oct 2010 for gridded products Global Precipitation Climatology Centre 35

data sources Temporal data coverage of the eight different data sources and the total GTS = near realtime SYNOP, CLIMAT Global Precipitation Climatology Centre 36

gridding Gridding of the stations monthly long-term mean data 1. Interpolation of station based monthly normals to gridpoint normals (distance of the grid-points 0.25 lat/lon) 2. Calculation of area-mean precipitation for regular grid-boxes for all continents and islands (grid size 0.5 lat by 0.5 lon, 1.0 lat by 1.0 lon, and 2.5 lat by 2.5 lon Gridding of the gauge data for individual months (e.g. July 2010) 1. Calculation of precipitation (mm/month) anomalies on the stations using all available data 2. Interpolation of station based monthly anomalies to grid-point anomalies and calculation of area means on the grid-boxes (as above) 3. Calculation of area-mean precipitation totals for the grid-boxes by combination of the gridded d anomalies and normals The anomaly-based interpolation is used at the GPCC since 2008 Global Precipitation Climatology Centre 37

quality control Loading new data check station meta data against the existing data Station with new data base he data b ons in th statio options decision support Questionable Meta Data o Expert Decision Global Precipitation Climatology Centre 38

quality control Major challenges: Metadata and precipitation Incorrect station location; observation data are intensively Separation of missing i quality controlled and if values from 0 mm; necessary corrected by GPCC Separation of true from based on automatic as well as false extremes; manual QC procedures Global Precipitation Climatology Centre 39

quality control Data errors discovered by comparisons and homogeneity tests Barisal, Maijde Court, Comilla/BGD: GHCN data for 1991-2000 too small by a factor*10!! Save/BEN: Reg. data for 1922-1924 and 1927-19361936 too large by a factor of 2.54!! Puna/BOL: FAO and GHCN data 1930-1948 do not belong there!! Cantillan/PHL: Nat. data 1977-1982 all 0!! Puerto Puyuhuapi, Coyhaique/CHL: Nat. data 1992-1995 all 0!! Global Precipitation Climatology Centre 40

Free access to GPCC gridded data sets via internet http://gpcc.dwd.de Number of contacts 2002-2008 Global Precipitation Climatology Centre 41