ARM/GCIP NESOB-97 Hourly Precipitation Composite 1.0 General Description The Hourly Precipitation Composite is one of several precipitation datasets provided in the GEWEX Continental-Scale International Project (GCIP) Near-Surface Observation Data Set (NESOB) 1997. This precipitation composite was formed from several data sources (i.e., National Climatic Data Center (NCDC) Hourly Precipitation dataset (TD 3240), National Centers for Environmental Prediction (NCEP), and the precipitation extracted from the NESOB 1997 Hourly Surface Composite). Data from these sources were quality controlled and merged to form this precipitation composite. This composite contains data for the NESOB 1997 domain and time period (01 April 1997 through 31 March 1998). The NESOB 1997 domain is approximately 94.5 W to 100.5 W longitude and 34 N to 39 N latitude. 2.0 Detailed Data Description 2.0.1 NCDC Hourly Precipitation Algorithms The NCDC Hourly Precipitation dataset (TD 3240) is formed by retaining both incremental and accumulative precipitation values from the raw precipitation data. Both incremental and accumulative values are contained in the NESOB 1997 Hourly Precipitation Composite. If an accumulation period began prior to but continued into the beginning of the NESOB 1997 time period, the precipitation values in that accumulation period were reset to missing values. An accumulation period that began near the end of the NESOB 1997 time period, but continued after the end of the NESOB 1997 time period would also have its precipitation values reset to missing. 2.0.2 Hourly Precipitation Extract from NESOB 1997 Hourly Surface Composite This dataset is formed by extracting both incremental and accumulative precipitation data from the NESOB 1997 Hourly Surface Composite. Both incremental and accumulative values are contained in the NESOB 1997 Hourly Precipitation Composite. Refer to the NESOB 1997 Hourly Surface Composite description document for more information. 2.0.3 NCEP Hourly Precipitation Algorithms The NCEP Hourly Precipitation dataset was formed by extracting incremental precipitation values that fell on the hour. The value reported for any hourly observation represents data collected during the previous 60 minutes. 2.1 Detailed Format Description The NESOB 1997 Hourly Precipitation Composite contains seven meta- data parameters and three data parameters. The metadata parameters describe the date/time, network, station, and location at which the data was collected. The three data parameters repeat once for each UTC hour from 0000 through UTC hour 2300. Data reported for a designated hour represents data collected during the previous hour. All times are reported in UTC, and precipitation data values are reported in millimeters. A Quality Flag and a QC Code are assigned to each data value during the University Corporation for Atmospheric Research/Joint Office for Science Support (UCAR/JOSS) Quality Control (QC) processing. For a list of possible Quality Flag and QC Code values see the Quality Control Section 3.0. The table below details each parameter. Parameters Units ---------- ----- Date of Observation UTC Time of Observation UTC Network Identifier Abbreviation of platform name Station Identifier Network Dependent Latitude Decimal degrees, South is negative Longitude Decimal degrees, West is negative Station Occurrence Unitless Hourly Precip Value Millimeters Quality Flag See list of Definitions QC Code See list of Definitions 2.2 Data Remarks None. 3.0 Quality Control Processing This precipitation composite was formed from three datasets (i.e., National Climatic Data Center (NCDC) Hourly Precipitation dataset (TD 3240), National Centers for Environmental Prediction (NCEP), and the precipitation extracted from the NESOB 1997 Hourly Surface Composite). Each of these datasets was Quality Controlled independently. Gross limit checks were used to determine the quality of the data in the NESOB 1997 Hourly Precipitation Composite. Data values less than 20 millimeters were flagged as good. Any data value greater than or equal to 20 millimeters but less than 50 millimeters was flagged as questionable. Any data value greater than or equal to 50 millimeters was flagged as unlikely. Several questionable and unlikely data values were also manually inspected. After inspection, the quality control code and flag may have been manually updated to better reflect the likelihood of the actual occurrence of the precipitation value based on an isohyet analysis. The data were never changed, only flagged. Tables 1 and 2 contain the quality control codes and flags, respectively. After the datasets were merged to form the NESOB 1997 Hourly Precipitation Composite, a statistics program was executed to ensure that the quality of the individual datasets had been retained. Table 1 Quality Control Flag Description ------------ ----------- 0 No qualifier required 1 Accumulation period 2 End of Accumulation period 3 Deleted value. Original data was unreadable. 4 Trace of precipitation. 5 Probable amount as a result of melting frozen precipitation. 6 Suspect amount relative to time or period of occurrence. 7 Missing value Table 2 QC Code Description ------- ----------- U Unchecked G Good M Normally recorded but missing D Questionable B Unlikely N Not available or Not observed. X Glitch E Estimated C Reported precipitation value exceeds 9999.99 millimeters or was negative. T Trace precipitation amount recorded. I Derived parameter can not be computed due to insufficient data. 4.0 References National Climatic Data Center, 1986: Hourly Precipitation Data, TD 3240. National Climatic Data Center, Asheville, NC, 20 pp.