Climate Monitoring of Precipitation: The GPCC - Status and plans

Global Precipitation Climatology Centre

U. Schneider, A. Meyer-Christoffer, B. Rudolf

Deutscher WetterdienstDepartment Hydrometeorology

Meeting of CCl-Expert Team on „Climate Monitoring incl. the use of Satellite and Marine Data and Products“, 27-29 October 2009, Offenbach, Germany

• Outlook (New analysis products)

Outline

• Different user requirements

Near real-time analyses

• GPCC‘s current precipitation analysis products

• Data base and data sources available (near- and non-realtime)

Non real-time analyses

• Background and international integration

Climate Monitoring of Precipitation: The GPCC - Status and plans

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:

• Production of gridded data sets using objective analysis methods

• 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

International integration

Besides its function in GPCP the GPCC contributes also to GCOS and GTN-H (Global Terrestrial Network for Hydrology)

Since Jan. 2004 the GPCC has taken over the operation of the GCOSSurface 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

The features of gridded precipitation data as required by the users:

Homogeneity (for climate change and variability analysis)

All of these requirements cannot be met by one single gridded data set

==>

User requirements

Timeliness (for drought monitoring)

High resolution (for regional structures in global maps)

High accuracy (for verification of model results)

Special products have been designed and optimized with respect to the priorities as given by the application purpose

GPCC data sources

Non real-time: Additional data from ca. 185 countries International project data (GEWEX-related and other) Historical data collections (CRU, FAO, GHCN)

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)

Near real-time GTS data base

GPCC is providing the following gridded data sets on aquasi-operational basis (GTS data base):

Near real-time precipitation products

A First Guess of Monthly Precipitation Anomalies available within 5 days after the end of the month via internet, used for drought monitoring (e.g. by FAO).

The Precipitation Monitoring Product available within 2 months,used by GEWEX/GPCP as early in-situ reference.

GPCC‘s First Guess of precipitation anomalies

Monthly precipitation totals are calculated only if temporal coverage

by SYNOP reports in the month is at least 70%

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 of SYNOP 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.)

GPCC First Guess for Europe, August 2005

France and Iberian Peninsula are still dryer than normal

while Switzerland, southern Germany and the Balkans faced severe floods

Precipitation anomaly for August 2005

Availability: period Jan. 1986 up to Dec. 2006 (V.1) period Jan. 2007 up to June 2009 (V.2) within 2 months after the end of the month

GPCC‘s Precipitation Monitoring Product

GPCC‘s Monitoring Product V.2 is the in-situ component of the combined GPCP-V2.1 data set

Data base (monthly precipitation totals, ca. 7,500 stations): accumulated from SYNOP reports received via GTS at DWD, Offenbach a.M. accumulated from SYNOP reports received via GTS at NOAA, Washington D.C. received in CLIMAT reports via GTS at DWD, Offenbach, UKMO,

Exeter and JMA, Tokyo

GPCC data base for different products

Feb. 2005Sept. 2008

1986: Original start of evaluation period

Drop: Time delay of data

provided

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.

Non real-time precipitation products

GPCC‘s Full Data Reanalysis V.4

Full Data Product (Version 4, Sept. 2008) optimized for high spatial resolution and accuracy designed for model verification and hydrological studies

Data base: ca. 10,000-45,000 stations per 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

Availability: period Jan. 1901 up to Dec. 2007 on a 2.5°-, 1°- and 0.5°-grid

GPCC‘s new precipitation climatology: January

GPCC‘s new precipitation climatology: July

50-year Analysis (VASClimO) V1.1

Analysis of relative anomalies at the stations superimposed on background climatology of 28,000 stations

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: period Jan. 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

Additional analysis products of the GPCC

Since Jan. 2007 the following products are operationally available:

• weather-dependent correction of the systematic gauge- measuring error for the month,

• discrimination of different precipitation types (liquid, solid, mixed)

Outlook

Significant enlargement of GPCC‘s data base

==> Update of GPCC product suite

Further improvements of data base quality

Current GPCC data base for different products1986: Original start of

evaluation period

Drop: Time delay of data

provided

Current GPCC data base for different products

GPCC data base (according to data sources)

Monthly in-situ precipitation stations used currently at GPCC as basis for anomaly analyses (Number of stations: 50,650)

Near real-time and non real-time data

GPCC Climatological data base

Database for GPCC climatology: 2008

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)

GPCC Climatological data base

Outlook

• New Global Precip. Climatology (ca. 58,500 stations)

• Monitoring Product (Version 3, since Jan. 2007)

• VASClimO Analysis (Version 2, 1951-2005)

Planned new analysis products of the GPCC (in Dec. 2009-Feb. 2010):

• Full Data Reanalysis (Version 5, 1901-2007)

After vacant position in GPCC will be refilled by April 2010 analysis of daily precipitation will be restarted

http://gpcc.dwd.de

Access to GPCC‘s Precipitation Products

Additional material

GPCC‘s Precipitation Monitoring Product

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, and an additional manual QC of the data flagged as questionable

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 havean incomplete coverage of the month resulting in uncertainties

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 density depends on temporal and spatial resolution considered and desired accuracyof the product:

10% error on a 2.5° grid requires 40,000 stations!

(Fig. GPCC after WMO-No. 115, 1985)

New method for correction of systematic gauge measuring error

Difference of correction (%) for Jan. 2005Climatological - New method

Temperature anomalies for Jan. 2005 (from normals 1961-1990)

Large-scale coherent structures in the difference field of the correction between climatological approach and new method correspond to temperature anomalies

New method for correction of systematic gauge measuring error

Fraction of solid precipitation (%)

Jan. 2005 July 2005