ARM/GCIP NESOB-97 Fifteen Minute Precipitation Composite 1.0 General Description The Fifteen Minute 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 two data sources (i.e., National Climatic Data Center (NCDC) Fifteen Minute Precipitation data (TD 3260), and fifteen minute precipitation extracted from the Department Of Energy (DOE) Atmospheric Radiation Measurement Surface (ARMSFC) five minute surface data). 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 94.5W to 100.5 W longitude and 34N to 39 N latitude. 2.0 Detailed Data Description 2.0.1 NCDC Fifteen Minute Precipitation Algorithms The NCDC Fifteen Minute Precipitation dataset (TD 3260) 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 15-minute 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 15-Minute Precip extracted from ARMSFC 5-Minute Surface Data Each 15-minute precipitation incremental value in this dataset was formed by summing the 5-minute precipitation values extracted from the Department Of Energy (DOE) Atmospheric Radiation Measurement Surface (ARMSFC) five minute surface data. For example, the incremental value at 0015, is the sum of the 0005, 0010, and 0015 values from the ARMSFC five minute surface data. The value reported at any 15-minute observation represents data collected during the previous 15 minutes. 2.1 Detailed Format Description The NESOB 1997 Fifteen Minute Precipitation Composite contains seven metadata parameters and three data parameters. The metadata parameters describe the date/time, network, station and location at which the data were collected. The three data parameters repeat once for each fifteen minutes from UTC 0000 through UTC hour 2345. Data reported for a designated 15-minute observation represents data collected during the previous 15-minutes. 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 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 15 Minute 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 two datasets (i.e., NCDC Fifteen Minute Precipitation data (TD 3260), and the precipitation extracted from the ARMSFC five minute surface data). Each of these datasets was Quality Controlled independently. All datasets were Quality Controlled using the gross limit check method. Gross limit checks were used to determine the quality of the data in the NESOB 1997 Fifteen Minute Precipitation Composite. Data values less than 8 millimeters were flagged as good. Any data value greater than or equal to 8 millimeters but less than 18 millimeters was flagged as questionable. Any data value greater than or equal to 18 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 two datasets were merged to form the NESOB 1997 Fifteen Minute 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: 15 Minute Precipitation Data TD 3260. National Climatic Data Center, Asheville, NC, 19 pp.