GCIP LSA-E EAOP 1999 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) Large Scale Area-East (LSA-E) Enhanced Annual Observing Period (EAOP) 1999. 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, South East Michigan Council of Governments (SEMCOG) precipitation network, United States Department of Agriculture (USDA) Agricultural Research Service (ARS) North Appalachian Experimental Watershed Data (Coshocton), Integrated Flood Observing and Warning System (IFLOWS) precipitation data, and the hourly precipitation extracted from the GCIP LSA-E EAOP-99 Hourly Surface Composite). Data from these sources were quality controlled and merged to form this precipitation composite. This composite contains data for the GCIP LSA-E EAOP-99 domain and time period (01 October 1998 through 30 September 1999). The GCIP LSA-E EAOP-99 domain is approximately 76W to 89W longitude and 33N to 43N 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 GCIP LSA-E EAOP-99 Hourly Precipitation Composite. If an accumulation period began prior to but continued into the beginning of the GCIP LSA-E EAOP-99 time period, the precipitation values in that accumulation period were reset to missing values. An accumulation period that began near the end of the GCIP LSA-E EAOP-99 time period, but continued after the end of the GCIP LSA-E EAOP-99 time period would also have its precipitation values reset to missing. For more information on the NCDC Hourly Precipitation dataset, TD 3240, see NCDC, 1986. 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. Data from cooperators networks such as NCEP/CPC has hundreds of reporting locations change from incremental to accumulator and back to incremental. Others, especially NCEP/CPC stations in West Virgina and Western portions of Pennsylvania changed a couple of times and have now settled on accumulators. Anyone using this data must be aware of the dynamic changes in the network of sites that are processed by HADS...and be aware of the potential lag time from when a change is implemted to when we become aware of the change. This is far, far from a stable environment. To help users in identifying these changes, 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. 2.0.5 South East Michigan Council of Governments (SEMCOG) Algorithms The SEMCOG precipitation gages are unheated, but the data has been corrected for freezing precipitation. The SEMCOG Home Page is at http://www.semcog.org. A map of the stations can be found at http://climate.geo.msu.edu/semcog/sem/Maps/1999/Actstn99.gif 2.0.6 United States Department of Agriculture (USDA) Agricultural Research Service (ARS) North Appalachian Experimental Watershed (NAEW) Data (Coshocton) Precipitation is measured using a Belfort FW1 weighing bucket. The sensor is not heated. Precip on/off is detected every 10 seconds using a Wong precipitation sensor. The USDA/ARS NAEW website is http://www.ars-grin.gov/naew. 2.0.7 Integrated Flood Observing and Warning System (IFLOWS) Algorithms Precipitation is gathered using a radio reporting tipping bucket rain gage. This type of gage is the most common type of sensor in this network. The gage reports real time (as it happens) rainfall in increments of 0.04 inches. When 0.04 inches of rain accumulate, the bucket tips and the transmitter sends out a signal consisting of a Gage ID (GID) and a counter value corresponding to each tip of the bucket. This coded message (raw rain gage data) is processed by the IFLOWS software and stored in the IFLOWS data base. For more information, visit the IFLOWS website at http://www.afws.net. 2.0.8 Hourly Precipitation Extract from GCIP LSA-E EAOP-99 Hourly Surface Composite This dataset is formed by extracting both incremental and accumulative precipitation data from the GCIP LSA-E EAOP-99 Hourly Surface Composite. Both incremental and accumulative values are contained in the GCIP LSA-E EAOP-99 Hourly Precipitation Composite. Refer to the GCIP LSA-E EAOP-99 Hourly Surface Composite description document for more information. 2.1 Detailed Format Description The GCIP LSA-E EAOP-99 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 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 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, South East Michigan Council of Governments (SEMCOG) precipitation network, United States Department of Agriculture (USDA) Agricultural Research Service (ARS) North Appalachian Experimental Watershed Data (Coshocton), Integrated Flood Observing and Warning System (IFLOWS) precipitation data, and the hourly precipitation extracted from the GCIP LSA-E EAOP-99 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 GCIP LSA-E EAOP-99 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. 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. 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 GCIP LSA-E EAOP-99 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.