ARM/GCIP NESOB-96 NCDC Evaporation Dataset 1.0 General Description The National Climatic Data Center (NCDC) Evaporation Dataset is one of several surface datasets provided for the GEWEX Continental- Scale International Project (GCIP) Near Surface Observation Data Set (NESOB) 1996 project. This dataset was formed by extracting evaporation data from the GCIP/Enhanced Seasonal Observing Period 1996 (GCIP/ESOP-96) NCDC Summary of the Day Co-operative Dataset (TD- 3200) for the NESOB 1996 area and time of interest. This NCDC Evaporation Dataset contains data from approximately 14 stations reporting evaporation data for the NESOB 1996 time period (01 April 1996 through 30 September 1996) and in the NESOB 1996 domain (approximately 94.5W to 100.5W longitude and 34N to 39N latitude). 2.0 Detailed Data Description The observations in this dataset are primarily those from the cooperative network, augmented by observations from principal observing stations operated by the National Weather Service (NWS) and other sites having highly trained observers. The primary thrust of the cooperative observing program today is the recording of 24-hour precipitation amounts, but a select group of the stations also record evaporation data. The observations are for the 24-hr period ending at the time of observation. Observer convenience or special program needs mean that observing times vary from station to station. However, the vast majority of observations are taken near either 7:00 AM or 7:00 PM local time. Details of procedures and recording practices of the observers are documented in the "National Weather Service Observing Handbook No. 2". The daily observations were processed at the National Climatic Data Center (NCDC) using computerized editing procedures. The data were subjected to internal consistency checks, compared against climatological limits, checked serially, and evaluated against surrounding stations. Quality control flags were appended to each element to show how they fared during the edit procedures and to indicate what, if any, action was taken. The data then, consist of observed values and, as necessary, best guess estimates (NCDC, 1991). 2.1 Detailed Format Description The NCDC Evaporation Dataset contains seven metadata parameters and sixteen data parameters and flags. The metadata parameters describe the date, network, station and location at which the data were collected. Data values are valid for the 24 hours preceding the time of observation. All times are UTC. The evaporation and temperature parameters are not reported whcn the temperature is below freezing. Table 1 below details the data parameters. The data parameters have two associated NCDC Quality Control (QC) Flags. A description of the possible QC flag values is listed in Tables 2 and 3. Table 1 ------- 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 Station Elevation Meters Evaporation Millimeters QC1, QC2 flags (See Tables 2 and 3.) Time of Observation UTC Maximum Temperature of water in pan Celsius QC1, QC2 flags (See Tables 2 and 3.) Time of Observation UTC Minimum Temperature of water in pan Celsius QC1, QC2 flags (See Tables 2 and 3.) Time of Observation UTC 24 hour Wind Movement Miles QC1, QC2 flags (See Tables 2 and 3.) Time of Observation UTC Table 2 ------- QC1 flag value Description -------------- ----------- 0 Reserved 1 Accumulated amount since last measurement 2 Accumulated amount includes estimated value 3 Estimated 4 Value has been manually validated 5 Included in a subsequent value 6 Trace 7 Expert system edited not validated 8 Expert system approved edited value 9 Flag not needed 11-255 Reserved Table 3 ------- QC2 flag value Description -------------- ----------- 0 Reserved 1 Valid data element 2 Valid data element from unknown source 3 Invalid data element replacement follows 4 Invalid data element no replacement follows 5 Validity unknown, not checked 6 Original value has been replaced by numeric value 7 Substituted TOBS for TMAX or TMIN 8 Time Shifted Value 9 Precipitation estimated by snowfall 10 Transposed digits 11 Changed units 12 Adjusted TMAX or TMIN by a multiple of + or - 10 degrees. 13 Changed algebraic sign 14 Moved decimal point 15 Rescaling other than 12, 13, or 14 16 Subjectively derived value 17 Extracted from an accumulated value 18 Switched to TMAX and or TMIN 19 Switched TOBS with TMAX or TMIN 20 Substitution of 3 nearest station mean 21 Switched snow and precipitation data value 22 Added snowfall to snow depth 23 Switched snowfall and snow depth 24 Precipitation not reported; estimated as "0" 25 Manually edited value 26 Failed internal consistency check 27 Failed areal consistency check (beginning Oct 92) 28-255 Reserved 2.2 Data Remarks The NCDC Evaporation Dataset hour of observation varies by station. 3.0 Quality Control Processing Quality Control for this data was provided by NCDC. No additional QC was performed by University Corporation for Atmospheric Research/Joint Office for Science Support (UCAR/JOSS) on this dataset. 4.0 References National Climatic Data Center, 1991: Surface Land Daily Cooperative; Summary of the Day TD-3200. National Climatic Data Center, Asheville, NC, 25pp. NOAA, National Weather Service, 1989: National Weather Service Observing Handbook No. 2, Cooperative Station Observations. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Weather Service, Silver Spring, MD. 83 pp.