ESOP 1998 Daily Precipitation Composite 1.0 General Description The ESOP 1998 Daily 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 is composed of data from stations from several sources (i.e., National Centers for Environmental Prediction/ Climate Prediction Center (NCEP/CPC) daily precipitation data, National Weather Service (NWS) Cooperative Observers (COOP) daily precipitation data, W.K. Kellogg Biological Stations (KELLOGG) daily precipitation data, and the daily precipitation data extracted from the ESOP 1998 Hourly Precipitation 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 NCEP/CPC Daily Precipitation Algorithms The NCEP/CPC daily precipitation dataset was formed by extracting data with NCEP/CPC element codes of PC and PP that fall on the hour. The NCEP/CPC observations of daily precipitation can include multiple measurements for a given day. When this occurs, the precipitation for that day is set to missing in the UCAR/JOSS ESOP 1998 Daily Precipitation Composite. The value reported for any daily observation represents data collected during the previous 24 hours. NCEP/CPC excludes any precipitation value greater than 20 inches from the NCEP/CPC daily precipitation dataset. The information above was gathered from personal correspondence with NCEP/CPC during 1997 and 1998. UCAR/JOSS checks the NCEP/CPC daily 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 daily precipitation values potentially followed by additional identical values or values that increase over time. 2.0.2 NWS Cooperative Observer (COOP) Daily Precipitation Algorithms The NWS Cooperative Observer Daily Precipitation dataset 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 1998 Daily Precipitation Composite. 2.0.3 W.K. Kellogg Biological Stations (KELLOGG) Daily Precipitation Algorithms Daily precipitation from two Kellogg Biological Stations (KBS) (i.e., Pond Lab and LTER) were included in this ESOP-98 Daily 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. Daily precipitation data collected at the Kellogg LTER site has been quality checked by KBS. The daily precipitation data from the Kellogg Pond Lab site has not been verified by KBS. There are known errors in the Kellogg Pond Lab site data. For more information regarding the KBS data, please see the W.K. Kellogg Biological Stations LTER Home Page at http://lter.kbs.msu.edu. See section 3.0 for a description of the quality control processing performed on this data by UCAR/JOSS. 2.0.4 Daily Precipitation Extracted from ESOP 1998 Hourly Precipitation Composite Each daily precipitation incremental value in this dataset was formed by summing the 24 hourly precipitation values extracted from each ESOP 1998 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. UCAR/JOSS also checks the NCEP/CPC daily 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". 3.0 Quality Control Processing This precipitation composite was formed from several datasets (i.e., National Centers for Environmental Prediction/Climate Prediction Center (NCEP/CPC) daily precipitation data, National Weather Service (NWS) Cooperative Observers (COOP) daily precipitation data, W.K. Kellogg Biological Stations (KELLOGG) daily precipitation data, and the daily precipitation data extracted from the ESOP 1998 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. UCAR/JOSS also checks the NCEP/CPC daily 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 daily precipitation values potentially followed by additional identical values or values that increase over time. 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 1998 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 value exceeds output format field size or was negative precipitation. T Trace 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.