ESOP 1998 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) Enhanced Seasonal Observing Period (ESOP) 1998. 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/Climate Prediction Center (NCEP/CPC) hourly precipitation data, National Soil Tilth Laboratory (NSTL) hourly precipitation dataset, Park Falls Wisconsin Tower (WLEF_TOWER) meteorological dataset, W.K. Kellogg Biological Stations (KELLOGG) hourly precipitation dataset, and the hourly precipitation extracted from the ESOP 1998 Hourly Surface Composite). Data from these sources were quality controlled and merged to form this precipitation composite. This composite contains data for the ESOP 1998 domain and time period (01 October 1997 through 31 May 1998). The ESOP 1998 domain is approximately 85W to 99W longitude and 37N to 50N 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 ESOP 1998 Hourly Precipitation Composite. If an accumulation period began prior to but continued into the beginning of the ESOP 1998 time period, the precipitation values in that accumulation period were reset to missing values. An accumulation period that began near the end of the ESOP 1998 time period, but continued after the end of the ESOP 1998 time period would also have its precipitation values reset to missing. 2.0.2 National Centers for Environmental Prediction/Climate Prediction Center (NCEP/CPC) Algorithms The Climate Prediction Center (CPC) is a component of the National Centers for Environmental Prediction (NCEP). The NCEP/CPC 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. UCAR/JOSS checks the NCEP/CPC hourly precipitation data for possible accumulated values and resets the UCAR/JOSS Quality Control flags for all "unchecked", "good", and "trace" accumulated precipitation values in the NCEP/CPC network to "questionable". For this purpose, UCAR/JOSS defines accumulated precipitation to be six identical, sequential hourly precipitation values potentially followed by additional identical values or values that increase over time. 2.0.3 National Soil Tilth Laboratory (NSTL) Algorithms UCAR/JOSS receives hourly data from NSTL. NSTL summarizes these hourly values from 5-minute data values. Hourly precipitation is the sum of the 5-minute precipitation values for the proceeding hour. During winter conditions, NSTL hourly precipitation is missing. This information was gathered from personal correspondence with NSTL during 1997 and 1998. Since the precipitation gages in this network are not heated during the winter months, the UCAR/JOSS quality control flags for all "unchecked", "good", and "trace" precipitation values in the NSTL network have been reset to "questionable". For more information on the quality control performed on this network by UCAR/JOSS, please see section 3.0 below. 2.0.4 Park Falls, WI Tower (WLEF_TOWER) Algorithm The WLEF Tower is located on the site of the Chequamegon Ecosystem-Atmosphere Study (Cheas) in Park Falls, Wisconsin. Hourly precipitation is extracted from the source meteorological data set and included in this ESOP-98 Hourly Precipitation Composite. The source data were quality assured and controlled and then provided to UCAR/JOSS by Dr. Ken Davis of the Department of Soil, Water, and Climate at the University of Minnesota and Dr. Peter Bakwin of the NOAA Climate Monitoring and Diagnostics Laboratory (CMDL). Since the precipitation gages in this network are not heated during the winter months, the UCAR/JOSS quality control flags for all "unchecked", "good", and "trace" precipitation values in this WLEF_TOWER network have been reset to "questionable". For more information on the quality control performed on this network by UCAR/JOSS, please see section 3.0 below. Dr. Davis and Dr. Bakwin ask to be contacted and given proper attribution whenever the WLEF-Tower data is used. For further information on the WLEF-Tower source data, please contact Dr. Davis at E-Mail address: kdavis@soils.umn.edu or phone 612-625-2774, or address: 439 Borlaug Hall; 1991 Upper Buford Circle; University of Minnesota; St. Paul, MN 55108-6028. Dr Bakwin may be contacted at E-Mail address: pbakwin@cmdl.noaa.gov or phone 303-497-6773, or address: NOAA ERL R/E/CG1; 325 Broadway; Boulder, CO 80303. 2.05 W.K. Kellogg Biological Stations (KELLOGG) Algorithms Hourly precipitation from two Kellogg Biological Stations (KBS) (i.e., Pond Lab and LTER) were included in this ESOP-98 Hourly Precipitation Composite. Both KBS stations are run by Michigan State University and are located in Hickory Corners, Michigan. The Kellogg Pond Lab weather station records precipitation using a NovaLynx (Sierra Misco) 2500E12 model 12" diameter funnel tipping bucket which is heated in the winter. The Kellogg LTER station records precipitation with both a tipping bucket and a belfort rain gauge. The tipping bucket used at the Kellogg LTER weather station is a NovaLynx(Sierra Misco) 2500 model 8" funnel heated in winter. The tipping bucket at the Kellogg Pond Lab weather station is not quality controlled by KBS. The tipping bucket at the Kellogg LTER weather station is checked against the Kellogg Pond Lab tipping bucket and Kellogg LTER Belfort rain gauge. When the Kellogg LTER tipping bucket data did not correspond to the Kellogg LTER belfort rain gauge, the Kellogg LTER belfort rain gage data was used in the ESOP-98 Hourly Precipitation Composite. For more information regarding the KBS data, please see the W.K. Kellogg Biological Stations LTER Home Page at http://lter.kbs.msu.edu. 2.0.4 Hourly Precipitation Extract from ESOP 1998 Hourly Surface Composite This dataset is formed by extracting both incremental and accumulative precipitation data from the ESOP 1998 Hourly Surface Composite. Both incremental and accumulative values are contained in the ESOP 1998 Hourly Precipitation Composite. Refer to the ESOP 1998 Hourly Surface Composite description document for more information. 2.1 Detailed Format Description The ESOP 1998 Hourly 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 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 Since the precipitation gages in the NSTL and WLEF_TOWER networks are not heated during winter conditions, the UCAR/JOSS quality control flags for all "unchecked", "good", and "trace" precipitation values in the NSTL and WLEF_TOWER networks have been reset to "questionable". UCAR/JOSS also checks the NCEP/CPC hourly precipitation data for possible accumulated values and resets the UCAR/JOSS Quality Control flags for all "unchecked", "good", and "trace" accumulated precipitation values in the NCEP/CPC network to "questionable". For more information on the quality control performed on this network by UCAR/JOSS, please see section 3.0 below. 3.0 Quality Control Processing 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/Climate Prediction Center (NCEP/CPC) hourly precipitation data, National Soil Tilth Laboratory (NSTL) hourly precipitation dataset, Park Falls Wisconsin Tower (WLEF_TOWER) meteorological dataset, W.K. Kellogg Biological Stations (KELLOGG) hourly precipitation dataset, and the hourly precipitation extracted from the ESOP 1998 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 ESOP 1998 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. Since the precipitation gages in the NSTL and WLEF_TOWER networks are not heated during winter conditions, the UCAR/JOSS quality control flags for all "unchecked", "good", and "trace" precipitation values in the NSTL and WLEF_TOWER networks have been reset to "questionable". UCAR/JOSS also checks the NCEP/CPC hourly precipitation data for possible accumulated values and resets the UCAR/JOSS Quality Control flags for all "unchecked", "good", and "trace" accumulated precipitation values in the NCEP/CPC network to "questionable". For this purpose, UCAR/JOSS defines accumulated precipitation to be six identical, sequential hourly precipitation values potentially followed by additional identical values or values that increase over time. 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 ESOP 1998 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 value exceeds output format field size or was negative precipitation. 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.