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