GIDS-1 Daily Precipitation Composite 1.0 General Description The Daily Precipitation Composite is one of two precipitation datasets provided as part of the GEWEX Continental-scale International Project (GCIP) Initial Dataset One (GIDS-1). This precipitation composite is composed of data from thousands of stations from several sources (i.e., Daily totals computed from GIDS-1 Hourly Precipitation Composite, United States Geological Survey (USGS) daily precipitation, Tennessee Valley Authority (TVA) daily precipitation, and the Daily precipitation extracted from the NCDC Cooperative data). Data from these sources were merged and quality controlled to form this precipitation composite. This composite contains data for the GIDS-1 time period (01 February 1992 through 30 April 92) and for the GIDS-1 area of interest, only. The GIDS- 1 area is approximately 85W to 106W longitude and 30N to 45N latitude. 2.0 Detailed Data Description The Daily Precipitation Composite format contains six metadata parameters followed by 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'). All records are identical in length. Each 24 hour precipitation value has an associated observation hour. The observation hour is the beginning 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. All times are reported in UTC. 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. 2.1 Data Remarks The length of the station identifier in the USGS precipitation data forces the composite station identifier field to be 15 characters . All other composites and datasets allow only 10 character station identifiers. 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 sub-datasets (i.e., Daily totals computed from GIDS-1 Hourly Precipitation Composite, USGS daily precipitation, TVA daily precipitation, and the Daily precipitation extract from the NCDC Cooperative data). Each of these sub-datasets was uniquely and 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 milli- meters 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. Data was 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'). A table of the possible quality control flags and their meanings is listed below. After the sub-datasets were merged to form the GIDS-1 Daily Precipitation Composite, a statistics program was executed to ensure that the quality of the individual sub-datasets had been retained. Quality Control Flag Description 0 No qualifier required 1 Accumulation period 2 End of Accumulation period 3 Deleted value. Original data was unreadable. 4-6 Reserved 7 Missing value 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 value exceeds 9999.99 millimeters or was negative. Data changed to -999.99. T Trace precipitation amount recorded 4.0 References For additional station information, refer to the station list provided as a seperate dataset in CODIAC.