ESOP 1996 Daily Precipitation Composite 1.0 General Description The ESOP 1996 Daily Precipitation Composite is one of several precipitation datasets provided in the GEWEX Continental-Scale International Project (GCIP) Enhanced Seasonal Observing Period (ESOP) 1996. This precipitation composite is composed of data from over a thousand stations from several sources (i.e.,Arkansas-Red River Basin River Forecast Center (ABRFC), National Weather Service (NWS) Cooperative Observers, and the daily precipitation data extracted from the ESOP 1996 Hourly Precipitation Composite). Data from these sources were quality controlled and merged to form this precipitation composite. This composite contains data for the ESOP 1996 domain and time period (01 April 1996 through 30 September 1996). The ESOP 1996 domain is approximately 91W to 107W longitude and 31N to 40N latitude. 2.0 Detailed Data Description 2.0.1 ABRFC Daily Precipitation Algorithms The ABRFC Daily Precipitation dataset was formed by extracting accumulative precipitation values that fell on the 0000 hour of each day. Incremental values were computed by differencing consecutive pairs of these accumulated values. The incremental value reported for any daily observation represents data collected during the previous 24 hours. Only incremental values are included in the ESOP 1996 Daily Precipitation Composite. 2.0.2 NWS Cooperative Observer Daily Precipitation Algorithms The NWS Cooperative Observer Daily Precipitation was formed by extracting the daily incremental precipitation values provided in the National Climatic Data Center (NCDC) TD 3200 dataset. The incremental value reported for any daily observation represents data collected during the previous 24 hours. Only incremental values are included in the ESOP 1996 Daily Precipitation Composite. 2.0.3 Daily Precip Extracted from ESOP 1996 Hourly Precipitation Composite Each daily precipitation incremental value in this dataset was formed by summing the 24 hourly precipitation values extracted from each ESOP 1996 Hourly Surface Composite record. The hourly values are summed from hour 0100 through hour 2400 (0000 UTC next day). The value reported for any daily observation represents data collected during the previous 24 hours. 2.1 Detailed Format Description The Daily Precipitation Composite contains six metadata parameters and four data parameters. The metadata parameters describe the station location and time at which the data were collected. The four data parameters repeat once for each day in the monthly record. Every record has 31 days reported, regardless of the actual number of days in the month. For months with less than 31 days, the extra days are reported as missing (i.e., '-999.99 7 M'). Each 24 hour precipitation value has an associated observation hour. The observation hour is the ending UTC hour for the 24 hour period for which the precipitation value is valid. Data values are valid for the 24 hours preceding the observation hour given for the day. A Quality Flag and a Quality Control (QC) Code are assigned to each data value during quality control 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 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 Daily Precip Value millimeters Quality Flag See list of Definitions QC Code See list of Definitions Observation hour Beginning UTC hour for 24 hour period for which value is valid. 2.2 Data Remarks Negative precipitation and values too large to be represented in the output format were changed to missing ('-999.99') and were assigned the 'C' QC code. The NCDC Summary of Day Co-operative data have observation hours that vary by station. Data values are valid for the 24 hours preceding the observation hour given for the day. 3.0 Quality Control Processing This precipitation composite was formed from several datasets (i.e., Arkansas-Red River Basin River Forecast Center (ABRFC) Daily Precipitation data, NWS Cooperative Observer Daily Precipitation data, and the Daily Precipitation extracted from the ESOP 1996 Hourly Precipitation Composite). Each of these datasets was independently Quality Controlled. Gross limit checks were used to determine the quality of the data in this composite. Data values less than 101.6 millimeters (4 inches) were flagged as good. Any data value greater than or equal to 101.6 millimeters but less than 127 millimeters (5 inches) was flagged as questionable. Any data value greater than or equal to 127 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. Data were never modified, unless the precipitation value was negative or too large to be represented in the output format. In these cases the data value was flagged with a QC code of 'C' and changed to a missing value (i.e., '-999.99'). Table 1 and 2 list the quality control flags and codes plus their meanings. After the datasets were merged to form the ESOP 1996 Daily 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, 1991: Surface Land Daily Cooperative; Summary of the Day TD 3200. National Climatic Data Center, Asheville, NC, 25 pp.