Information on the daily precipitation analyses available from the U.S. Climate Prediction Center (CPC), can be found here: http://www.cpc.ncep.noaa.gov/products/precip/realtime/
Original documentation on the CPC Gauge-Based Analysis of Global Daily Precipitation can be found in the following location: ftp://ftp.cpc.ncep.noaa.gov/precip/CPC_UNI_PRCP/GAUGE_GLB/DOCU/.
The following information is excerpted from the "README" file associated with this dataset:
CPC Gauge-Based Analysis of Global Daily Precipitation
1) Product Name
CPC Unified Gauge-Based Analysis of Global Daily Precipitation
2) Background
This data set is the first product of the CPC Unified Precipitation
Project that are underway at NOAA Climate Prediction Center (CPC). The primary
goal of the project is to create a suite of unified precipitation products with
consistent quantity and improved quality by combining all information sources
available at CPC and by taking advantage of the optimal interpolation (OI)
objective analysis technique.
3) Coverage and Resolution
Space : 0.5deg lat / lon; Global Land
Time : Daily; Jan.1, 1979 - Present
1979 - 2005 : Rereospective Version (30K+ gauges)
2006 - Present : Real-time version (~17K gauges)
4) Cautions and Alerts
* Quality of the gauge-based analysis is poor over tropical Africa and
Antartica;
* Elsewhere, the analysis quality varies with the gauge network density.
Users are encouraged to take advantage of the network density
information included in the data file;
* Definition of the ending time for the daily accumulation differs from
country to country. There might be discontinuity in the analyzed
fields across the national boundaies;
5) Definition of the End of Day (EOD) time
The EOD time differs from country to country. A GrADS formatted binary
data file is included to indicate the definition of the EOD on each 0.5deg
lat/lon grid box. However, the EOD included in the file is based on very
limitted and UNCHECKED information that we have been able to get. Users
are encouraged to double-check the reliability of the information if accuracy
of the EOD is critical to their applications. Please report us any of your
findings regarding the error or suspicions with the EOD.
6) Data Files
* Document files are in sub-directory /docu
* Retrospective version data files are in sub-directory /v1.0
* Real-time version data files are in sub-directory /RT
6.1) End of Day (EOD) time file
PRCP_CU_GAUGE_V1.0GLB_0.50deg_EOD.lnx ----- Binary data file
PRCP_CU_GAUGE_V1.0GLB_0.50deg_EOD.lnx.ctl ----- GrADS control file
6.2) Analysis data files
* Data files for each calendar year are stored in a sub-directory 'yyyy'
where 'yyyy' is a 4-digit integer;
* Under each yearly sub-directory, analysis data for each day are
included in a single GrADS formatted data file named:
PRCP_CU_GAUGE_V1.0GLB_0.50deg.lnx.yyyymmdd ; or
PRCP_CU_GAUGE_V1.0GLB_0.50deg.lnx.yyyymmddRT
where 'yyyymmdd' denotes the target year, month, and date.
'RT' at the end of the file name indicates that the analysis for the
day is based on the real-time station data and the analysis will be
reprocessed later on when enhanced station data are available.
* In each daily file, there are two global fields:
analyzed field of daily precipitation in 0.1mm; and
number of gauges available in each 0.5deg lat/lon grid box.
* The global field starts from the 0.5deg lat/lon grid box centering
at (0.25E; 89.75S), going from west to east first, and then south to
north.
* Both the global fields are written as 4-byte real numbers in
LITTLE_ENDIAN byte order. You may need to swap the byte order if
you are working with a big_endian machine (such as an SGI).
* The following GrADS control file for the daily data is available:
PRCP_CU_GAUGE_V1.0GLB_0.50deg.lnx.ctl
6.3) Quality Check Report (QCR) file
An ASCII text file is included in each yearly sub-directory to list
the known problems / limitations with the analysis. The file is named:
PRCP_CU_GAUGE_V1.0GLB_0.50deg_QCR.txt.yyyy
These problems / limitations are discovered through manual checks by the
data producers.
7) References:
(Interpolation algorithm)
Xie_et_al_2007_JHM_EAG.pdf
Xie, P., A. Yatagai, M. Chen, T. Hayasaka, Y. Fukushima, C. Liu, and
S. Yang (2007), A gauge-based analysis of daily precipitation over East
Asia, J. Hydrometeorol., 8, 607. 626.
(Gauge Algorithm Evaluation)
Chen_et_al_2008_JGR_Gauge_Algo.pdf
Chen, M., W. Shi, P. Xie, V. B. S. Silva, V E. Kousky, R. Wayne Higgins,
and J. E. Janowiak (2008), Assessing objective techniques for gauge-based
analyses of global daily precipitation, J. Geophys. Res., 113, D04110,
doi:10.1029/2007JD009132.
(Construction of the Daily Gauge Analysis)
Chen_et_al_2008_Daily_Gauge_Anal.pdf
Chen, M., P. Xie, and Co-authors (2008), CPC Unified Gauge-based Analysis
of Global Daily Precipiation, Western Pacific Geophysics Meeting, Cairns,
Australia, 29 July - 1 August, 2008.
8) Contacts
Dr. Pingping Xie
Climate Prediction Center
5200 Auth Road, #605
Camp Springs, MD 20746
USA
E-Mail: Pingping.Xie@noaa.gov
Tel. (301)763-8000, #7572
Dr. Wei Shi
Climate Prediction Center
5200 Auth Road, #605
Camp Springs, MD 20746
USA
E-Mail: Wei.Shi@noaa.gov
Tel. (301)763-8000, #7545
Dr. Mingyue Chen
Climate Prediction Center
5200 Auth Road, #605
Camp Springs, MD 20746
USA
E-Mail: Mingyue.Chen@noaa.gov
Tel. (301)763-8000, #7506