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GES DISC DAAC Data Guide: GPCC Rain Gauge Analysis Data

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Summary:

This document contains information on the structure of the Global Precipitation Climatology Center (GPCC) global rain gauge analysis dataset and and pertinent scientific references.

The global land surface precipitation data set is comprised of monthly mean rainfall totals on a 2.5 degree by 2.5 degree grid for the period 1986 to 1996. The grid cell-related area-mean precipitation is based on rain gauge observations from about 6,700 meteorological stations.

Table of Contents:

1. Data Set Overview:

Data Set Identification:

Global Precipitation Climatology Center Global Rain Gauge Analysis Data

Data Set Introduction:

The land surface precipitation data set covering all continents is comprised of monthly gridded area-mean rainfall totals for the period 1986 to 1996. The grid size is 2.5 degree latitude by 2.5 degree longitude. The gridded area-means are calculated from high-level quality-controled rain gauge measured data from about 6,700 meteorological stations using an objective interpolation scheme.

Objective/Purpose:

This data set was generated for the GPCP in an effort to provide global data sets of area-averaged and time-integrated precipitation data based on all suitable observation techniques.

The main applicatations of the land surface data set will be the verification of monthly satellite based precipitation estimates and large-scale hydrological studies.

Summary of Parameters:

The parameter for this data set is monthly average rainfall.

Discussion:

This information is not available at this time.

Related Data Sets:

Jaeger Monthly Mean Global Precipitation
Legates Surface and Ship Observation of Precipitation

2. Investigator(s):

Investigator(s) Name and Title:

Dr. Bruno Rudolf
Global Precipitation Climatology Centre
at Deutscher Wetterdienst
Frankfurter Str. 135
D-63067 Offenbach am Main
Germany

Tel: + 49 - 69 - 8062 - 2765
Fax: + 49 - 69 - 8236 - 1493
email: brudolf@dwd.d400.de

Title of Investigation:

Global Precipitation Analysis Based on Observational Data

Contact Information:

Please direct all queries to Goddard Space Flight Center (GSFC) DAAC Help Desk.

DAAC Help Desk:

The DAAC help desk also provides additional information on the Goddard DAAC system capabilities, and other supported datasets. The Help Desk can be reached at:

EOS Distributed Active Archive Center (DAAC)
Code 610.2
NASA Goddard Space Flight Center
Greenbelt, Maryland 20771
Internet:daacuso@daac.gsfc.nasa.gov
301-614-5224 (voice)
301-614-5268 (fax)

3. Theory of Measurements:

This information is not available at this time.

4. Equipment:

Sensor/Instrument Description:

Collection Environment:

The collection environments for this data set includes Ground stations and ship.

Source/Platform:

The sources for this data set includes ship and Meterological Stations.

Source/Platform Mission Objectives:

This information is not available at this time.

Key Variables:

Monthly Mean Precipitation

Sensor/Instrument Measurement Geometry:

This information is not available at this time.

Manufacturer of Sensor/Instrument:

This information is not available at this time.

Calibration:

Specifications:

This information is not available at this time.

Tolerance:

This information is not available at this time.

Frequency of Calibration:

This information is not available at this time.

Other Calibration Information:

This information is not available at this time.

5. Data Acquisition Methods:

The monthly preciptation totals based on conventional measurements are available from CLIMAT reports or can be calculated from SYNOP reports disseminated via the World Weather Watch Global Telecommunication System for about 4000 stations worldwide. Some additional station data has been included in this global data set and were supplied by several counties (Australia, Ghana, Great Britain, Russia, the Netherlands, New Zealand, and the United States).

6. Observations:

Data Notes:

This information is not available at this time.

Field Notes:

This information is not available at this time.

7. Data Description:

Spatial Characteristics:

Spatial Coverage:

The land surface data set contains global gridded rainfall estimates. The data progresses from North to South and West to East with the first value centered at 88.75 degrees North and 178.75 degrees West. Grids with no data are filled by missing codes.

Spatial Coverage Map:

The data coverage is global. However, for this land surface precipitation data set, grids over oceans with no data are set to a missing value code (-99999.99).

Spatial Resolution:

The spatial resolution of the data is 2.5 degree latitude by 2.5 degree longitude grid boxes.

Projection:

Cylindrical Equidistant.

Grid Description:

The grid resolution is 2.5 degree latitude by 2.5 degree longitude. Data grids run in the order from North to South and West to East.

The following diagram schematically depicts the data grid.

180W/90N 0 180E/90N
     |--------------------------------------------------------------------| 
     | 1. val. | 2. val. |   *    |   *     |    *    |   *     | 144.val.|
     |--------------------------------------------------------------------|
     | 145.val.|    *    |   *    |   *     |    *    |   *     |    *    | 
     |--------------------------------------------------------------------|
     |    *    |    *    |   *    |   *     |    *    |   *     | 10368.  |
     |--------------------------------------------------------------------|
180W/90S 0 180E/90S
For example, i=145.value is the index for the 2.5 latitude/longitude box centered at 178.75 W/86.25 N. The #.value is the rainfall estimate, the number of stations used in the objective analysis or indication of other data sources.

Temporal Characteristics:

Temporal Coverage:

For this land surface data set, the temporal coverage is from 1986 through 1996.

Temporal Coverage Map:

The temporal coverage for the land surface precipitation data set is from 1986 to 1996. No maps are available at this time

Temporal Resolution:

The data set contains monthly rainfall estimates.

Data Characteristics:

Parameter Average Monthly Rainfall Definition Monthly average of rainfall Units of Measurement	mm/month Data Source The estimates over land are based on rain gauge data Data Range 0 - 10000.0 mm/month	

			-99999.99 = missing code

Sample Data Record:

The following is sample of a partial month (December, 1992) of the land surface only monthly rainfall data set in ASCII format.

-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0
-99999.99 0 3.84 0 3.98 0 4.11 0 4.22 0 4.35 0 4.48 0 4.62 0 4.74 0 4.88 0 4.97 0 5.01 0
-99999.99 0 5.06 0
-99999.99 0 5.10 0 5.17 0 5.24 0 5.30 0

8. Data Organization:

Data Granularity:

A general description of data granularity as it applies to the IMS appears in the EOSDIS Glossary.

There are two files for each month of data. The data file and error file. The error file is independent of year.

Data Format:

The GPCC global precipitation data set is available in ASCII format.

9. Data Manipulations:

Formulae:

Derivation Techniques and Algorithms:

For objective analysis (interpolation of station-related point data to a regular grid with mesh of 0.5 degree by 0.5 degree) the code SPHEREMAP is used, which was developed by Willmott et al. (1985) based on Shepards interpolation scheme (1968), provided by Legates to GPCC in 1990, adjusted by GPCC for operational use (Rudolf et al. 1992).

Data Processing Sequence:

Processing Steps:

The processing steps for the data set are:

1. reformatting of the acquired station-related data,

2. control of the meta-data (station coordinates),

3. filling the precipitation point data bank (PDB), i.e. merging the station-related data from different sources (GTS, national data sets, other collections) to one worldwide data set,

4. first objective analysis using the uncontrolled precipitation records,

5. automatic quality control of the precipitation records (comparison with area means from step 4 and station-related climatic means),

6. visual expert quality control and interactive correction with graphical workstation assistance (comparison with climate maps, orographical data, extrem-event-catalogs, etc.),

7. second objective analysis using the controlled precipitation data,

8. filling the results of the second analysis run (step 7) into precipitation grid data bank (GDB),

9. correction of the results from step 8 with regard to systematic measuring errors,

10. calculation of the grid-related stochastic error of the precipitation results (step 8) from station density, precipitation variance fields, individual data uncertainties, and uncertainty of the systematic measuring error corrections.

NOTES:
	ad 1. Gauge measurements from world-wide about 6700 stations, inter-
             polated by the SPHEREMAP code (Shepard 1968, Willmott et al. 1985)
             - interpolation for Antarctica was made separately from the interpolation run for the other continents to avoid any in-
               fluence of far distant stations.
 

Processing Changes:

This information is not available at this time.

Calculations:

Special Corrections/Adjustments:

This information is not available at this time.

Calculated Variables:

(1) Monthly area-mean precipitation totals on grid

(2) Number of rain gauge stations per grid related to (1)

(3) stochastic error of (1)

Graphs and Plots:

No graphs or plots are available.

10. Errors:

Sources of Error:

Sources of error include:

- coding errors in the original station-related observational data,

- systematic measuring errors (wind influence, evaporation),

- sampling errors (incomplete station-related recordings, network density),

- methodical analysis errors.

Quality Assessment:

Data Validation by Source:

This information is not available at this time.

Confidence Level/Accuracy Judgement:

The size of the stochastic relative error is mainly dependent on the reginal network density and snow/rain ratio and is ranges from less than five percent to greater than fifty percent.

Measurement Error for Parameters:

This information is not available at this time.

Additional Quality Assessments:

This information is not available at this time.

Data Verification by Data Center:

The GSFC DAAC completes visual inspection of the data files that comprise the data set to ensure that the data set is complete and that the files were not corrupted during the file transfer from the data producer.

11. Notes:

Limitations of the Data:

This information is not available at this time.

Known Problems with the Data:

This information is not available at this time.

Usage Guidance:

This information is not available at this time.

Any Other Relevant Information about the Study:

This information is not available at this time.

12. Application of the Data Set:

The main applicatations of the land surface data set will be the verification of monthly satellite based precipitation estimates and large-scale hydrological studies.

13. Future Modifications and Plans:

The data producer provides periodic updates to the data set with increased temporal coverage. The GSFC DAAC will work with the data producer to include the additional data in the archive.

14. Software:

Software Description:

Software is presently not available

15. Data Access:

Contact Information:

Goddard Space Flight Center DAAC User Services.

Data Center Identification:

GSFC Distributed Active Archive Center

Procedures for Obtaining Data:

This data set is available via several ways: by contacting the GSFC DAAC User Services, by accessing the DAAC/EOSDIS Archive Search and Order Utilities, the WWW interface, or Anonymous FTP.

GSFC DAAC User Services:

The DAAC User Services or Help Desk also provides additional information on the Goddard DAAC system capabilities, and other supported datasets. The Help Desk can be reached at:
     EOS Distributed Active Archive Center (DAAC)
     Code 610.2 NASA Goddard Space Flight Center Greenbelt, Maryland 20771 Internet:daacuso@daac.gsfc.nasa.gov
     301-614-5224 (voice)
     301-614-5268 (fax)
       
     

DAAC SEARCH AND ORDER SERVICES:

The Goddard DAAC maintains archives of these datasets. The data stored in our archives can be ordered 4mm/8mm cartridges using any of the following search and order utilities 1) GSFC DAAC IMS (Character Based):
telnet daac.gsfc.nasa.gov login as: daacims password: gsfcdaac

2) EOSDIS V0 IMS (Web Based): http://eos.gsfc.nasa.gov/imswelcome/

3) EOSDIS V0 IMS (X-window) : telnet eosims.gsfc.nasa.gov:12345

ANONYMOUS FTP:

The Precipitation Global Data Set also resides on-line at the Goddard DAAC anonymous FTP and may be accessed either directly from this document, FTP GIFGPCC Global Rain Gauge Analysis Data

or can be acessed via FTP at

ftp daac.gsfc.nasa.gov
login: anonymous
password: > your internet address <
cd http://disc.sci.gsfc.nasa.gov/data/hydrology/precip/gpcp/gpcc
mget *

Data Center Status/Plans:

The GSFC DAAC plans to periodically check with the data producer regarding updates to the data set.

16. Output Products and Availability:

Data sets are provided on 8 mm tapes, 4 mm tapes, or ftp .

17. References:

Adler, R.F., Huffman, G.J., Rudolf, B., Schneider, U., and Keehn, P.R.: A Technique for Combining Satellite Data, Raingauge Analysis, and Model Precipitation Information into Global Precipitation Estimates. In preparation.

GPCC (1992): Monthly precipitation estimates based on gauge measurements on the continents for the year 1987 (preliminary results) and future requirements. Ed. by WCRP and DWD, Rep.-No. DWD/K7/WZN-1992/08-1, Offenbach, August 1992.

Janowiak, J.E., and Arkin, P.A. (1991): Rainfall Variation in the Tropics during 1986-1989, as Estimated from Observations of Cloud-Top Temperature. J. Geophys. Res., 96, Supplement, 3359-3373.

Legates, D.R. (1987): A climatology of global precipitation. Publ. in Climatology, 40(1), Newark, Delaware, 88 pp.

Rudolf, B., Hauschild, H., Reiss, M. and Schneider, U. (1992): Beitrage zum Weltzentrum fur Niederschlagsklimatologie - Contributions to the Global Precipitation Climatology Centre. Meteorologische Aeitschrift N.F. 1(1), 7-84.

Wilheit, T.T., Chang, A.T.C., Chiu, L.S. (1991): Retrieval of Monthly Rainfall Indices from Microwave Radiometric Measurements Using Probability Distribution Function. J. Atm. Ocean. Tech. 8, 118-136.

Willmott, C.J., Rowe, C.M., Philpot, W.D. (1985): Small-Scale Climate Maps: A Sensitivity Analysis of Some Common Assumptions Associated with Grid-Point Interpolation and Contouring. The American Cartographer, 12(1), 5-16.

WMO/ICSU (1990): The Global Precipitation Climatology Project - Implementation and Data Management Plan. WMO/TD-No. 367, Geneva, June, 1990.

18. Glossary of Terms:

EOSDIS glossary

19. List of Acronyms:

EOSDIS acronyms

GPCP

Global Precipitation Climatology Project

GPCC

Global Precipitation Climatology Center

URL

Uniform Resource Locator

20. Document Information:

Document Revision Date:Fri May 10 11:52:34 EDT 2002
August 21, 1997

Document Review Date:

August 21, 1997

Document ID:

This information is not available at this time.

Citation:

This information is not available at this time.

Document Curator:

Hydrology Data Support Team
hydrology@daac.gsfc.nasa.gov

Document URL:

/DATASET_DOCS/gpcc_rain_gauge_dataset.html

Change History

Version 2.0
Version baselined on addition to the GES Controlled Documents List, August 21, 1997.
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