Status and Plans of the Global Precipitation Climatology Centre (GPCC)

Bruno Rudolf, Tobias Fuchs and Udo Schneider (GPCC)

Overview:

• Introduction to the gauge-based gridded precipitation data sets

• Development of the observational database

• Climatological evaluation of the time-series

• Systematic measuring error with a focus on solid precipitation

• Outlook

Monitoring ProductPurpose: Precipitation Monitoring(input to GPCP and CMAP)

First Guess ProductPurpose: Drought Monitoring(by FAO and other institutes)

Available spatial resolutions: 1.0° and 2.5° lat/long(GPCC-internally calculated on 0.5° lat/long)

Available: 2 months laterData base: 6,500 to 7,000 stations Data sources: SYNOP data plus

monthly CLIMAT and CPC

Quality control: automatic and visual Available products: from Jan. 1986 onwards up to near present

Available: 3 - 5 days after end of monthData base: 5,500 stations Data source: SYNOP data only Quality control: automatic onlyAvailable products: Only the current product

Monthly Operational GPCC Products (near real-time)

Full Data ReanalysisPurpose: verification of models

continental water cycle studies

UNESCO, GTN-H, GRDC

Use of all data being available at GPCC- Current version 3 based includes

up to 43,000 stations in one month

- Period: 1951 - 2004

- Quality control/assurance for meta data and

monthly precipitation data

50-Year Climatology Purpose: variability studies

trend analysis

(GCOS, IPCC)

available since Apr 2005

Use of selected data time-series- Current Version 1.1 with 9,343 stations

- Period 1951 - 2000

- High level quality and homogeneity control

- Analysis based on climatic background

Updates after significant improvements of the data base (about once per year)

Available spatial resolution: 0.5°, 1.0° and 2.5° Lat/Lon

GPCC Data Reanalysis Products

Standard GPCC products provided on the grid:

monthly precipitation total

number of stations

monthly precipitation anomaly

Normals:Mean monthly precipfrom 1961 to 1990based on 30.000 stations

absolute measuring error (mm/mon) relative measuring error (%)

fraction of solid precipitation (%)fraction of liquid precipitation (%)

New GPCC products based on daily synoptic data

Will be included to the web pages Visualizer soon

Status and Plans for the Global Precipitation Climatology Centre (GPCC)

Bruno Rudolf, Tobias Fuchs and Udo Schneider (GPCC)

Overview:

• Introduction to the gauge-based gridded precipitation data sets

• Development of the observational database

• Climatological evaluation of the time-series

• Systematic measuring error with a focus on solid precipitation

• Outlook

Development of the GPCC database

Status in 2001

data collected for the period from 1986 onwards

as requested by GEWEX

Decline of data after 1986 due to data delivery delays of the participating countries

Development of the GPCC database

Collection of long time-series following the request of GCOS and promoted by the AOPC

Status of January 2006

The current database of GPCC‘s products

Number of stations being selected for the different productsin the course of time (status of February 2005)

176 countries delivering data to GPCCUsual delay in data delivery approx. 1 to 5 years

The GPCC database in preparation

/ / / / / / / / / - additional data received in 2006, currently being processed (partly overlapping, partly complementing the existing data)

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Status and Plans for the Global Precipitation Climatology Centre (GPCC)

Bruno Rudolf, Tobias Fuchs and Udo Schneider (GPCC)

Overview:

• Introduction to the gauge-based gridded precipitation data sets

• Development of the observational database

• Climatological evaluation of the time-series

• Systematic measuring error with a focus on solid precipitation

• Outlook

- monthly precipitation total

- interpolation error

- only station data with a minimum of 90% data availability

- 50 year mean precipitation - standard deviation

- absolute trend - relative trend

- trend significance - trend/noise ratio- variation coefficient

Variables available on a 0.5° grid: 1951 to 2000

Time-series (600 months)

Statistical results forthe months and the year

VASClimO: A homogenised 50-Year Climatology

based on 9,343 selected stations

Seasonal precipitation trends 1951-2000 over Northern and Southern Europe

50-Year Climatology: Overall Results

Results from GPCC project VASClimO (C. Beck, J. Grieser and B. Rudolf, 2005)

spring

winterautumn

summer

Mean precipitation (all continents) for the 1951-2000 climatology complemented by the 2001-2005 near real-time Monitoring Product

Monthly area mean anomaly and 12 months running mean

Monthly area mean precipitation and 12 months running mean

The real-time data do not fit the homogenized time-series !!

Status and Plans for the Global Precipitation Climatology Centre (GPCC)

Bruno Rudolf, Tobias Fuchs and Udo Schneider (GPCC)

Overview:

• Introduction to the gauge-based gridded precipitation data sets

• Development of the observational database

• Climatological evaluation of the time-series

• Systematic measuring error with a focus on solid precipitation

• Outlook

Systematic Gauge Measuring Error

The problem:

Precipitation amounts measured by raingauges are systematically underestimated.

For estimation of reliable global or regional precipitation amounts, an adequate correction of the data used or of the product is required.

(Fig. after SEVRUK 1989)

Precipitation phase and windspeed are the most important parameters for correction of raingauge observations

Correction ratio in % of the data measured by the Hellmann gauge (without windshield)

as a function of wind speed for solid, liquid and mixed precipiation

(T. Günther, DWD, in Goodison et al. WMO 1998)

Mean correction factors for the area of Europe:• Monthly long-term mean error estimate after Legates• Error calculated from daily SYNOP and its monthly means for 2001• Large for snow regions and cold season

Systematic error correction factors for Europe

Many non-synop stations are located in gardens, villages etc.and well protected from wind effects by vegetation.

(here: Climate Reference Station Asheville NC)

Meta Data Information:type of gauge usedsourrounding properties

Status and Plans for the Global Precipitation Climatology Centre (GPCC)

Bruno Rudolf, Tobias Fuchs and Udo Schneider (GPCC)

Overview:

• Introduction to the gauge-based gridded precipitation data sets

• Development of the observational database

• Climatological evaluation of the time-series

• Systematic measuring error with a focus on solid precipitation

• Outlook

1. Users of gridded GPCC gauge data sets should not use any product but should reflect their application purpose and select the optimized product (best spatial coverage or best homogeneity).

Conclusions and Outlook

1. Users of gridded GPCC gauge data sets should not use any product but should reflect their application purpose and select the optimized product (best spatial coverage or best homogeneity).

2. The real systematic gauge measuring error is smaller than the climatological estimates published by Legates & Willmott (1989).

Conclusions and Outlook

1. Users of gridded GPCC gauge data sets should not use any product but should reflect their application purpose and select the optimized product (best spatial coverage or best homogeneity).

2. The real systematic gauge measuring error is smaller than the climatological estimates published by Legates & Willmott (1989).

3. The instrument type and the local environment is unknown for most of the gauge stations. Even with the new method, the calculated gauge error is a rough bias estimate.

Conclusions and Outlook

1. Users of gridded GPCC gauge data sets should not use any product but should reflect their application purpose and select the optimized product (best spatial coverage or best homogeneity).

2. The real systematic gauge measuring error is smaller than the climatological estimates published by Legates & Willmott (1989).

3. The instrument type and the local environment is unknown for most of the gauge stations. Even with the new method, the calculated gauge error is a rough bias estimate.

4. The GPCC data base is still growing. In particular, the collection of precipitation normals will increase to about 50,000 stations. The normals will be analysed on the orographic background.

Conclusions and Outlook

1. Users of gridded GPCC gauge data sets should not use any product but should reflect their application purpose and select the optimized product (best spatial coverage or best homogeneity).

2. The real systematic gauge measuring error is smaller than the climatological estimates published by Legates & Willmott (1989).

3. The instrument type and the local environment is unknown for most of the gauge stations. Even with the new method, the calculated gauge error is a rough bias estimate.

4. The GPCC data base is still growing. In particular, the collection of precipitation normals will increase to about 50,000 stations. The normals will be analysed on the orographic background. 5. In future, all GPCC products will be calculated using high-resolution climatological precipitation fields as analysis background

Conclusions and Outlook

Status and Plans of the Global Precipitation Climatology Centre (GPCC)

Thank you for your attention!

More information from http://gpcc.dwd.de