Alan Rea and Robert L. Tortorelli 1999 Version 1.0, July 26, 1999 map USGS Open-File Report USGS OFR 99-463 Reston, VA U.S. Geological Survey http://water.usgs.gov/lookup/getspatial?ofr99-463_sites These geospatial data sets consist of precipitation stations used in a regional precipitation frequency analysis for Oklahoma. Data were used from precipitation gage stations with at least 10 years of record within Oklahoma and about 50 kilometers into bordering states. Three different rain gage networks provided the data (15-minute, 1-hour, and 1-day). Data were analyzed for seven frequencies (expressed as recurrence intervals of 2-, 5-, 10-, 25-, 50-, 100-, and 500-years) and 12 durations (15-, 30-, and 60-minutes; 1-, 2-, 3-, 6-, 12-, and 24-hours; and 1-, 3-, and 7-days). Precipitation annual maxima (depths) were determined from the station data for each duration for 110 15-minute stations (used for 15-, 30-, and 60-minute durations), 141 hourly stations (used for 1-, 2-, 3-, 6-, 12-, and 24-hour durations), and 413 daily stations (used for 1-, 3-, and 7-day durations). Statistical methods were used to estimate precipitation depths for each duration-frequency at each station. These station depth-duration-frequency estimates were interpolated to produce continuous grids with grid-cell spacing of 2,000 meters. Contour lines derived from these surfaces (grids) were used to produce the maps in the "Depth-Duration Frequency of Precipitation for Oklahoma" by R.L. Tortorelli, Alan Rea, and W.H. Asquith, U.S. Geological Survey Water-Resources Investigations Report 99-4232. Depth-duration-frequency estimates and interpolated surface values are included in the point attribute tables. One geospatial data set is provided for each of the 12 durations. These data sets were used to produce the maps in the Precipitation Atlas--Depth-Duration Frequency of Precipitation for Oklahoma (Tortorelli, Rea, and Asquith, 1999). L-moment statistical methods were used to estimate depth-duration-frequency relations for each precipitation station. See Tortorelli, Rea, and Asquith, (1999) for discussion of the statistical methods. L-coefficient of variation and L-skew were averaged for each station with its four nearest neighbors. The values were weighted by the number of years of record at each station. The means were not averaged. The IDW function in ARC/INFO was used with an exponent of zero to average the values for each point and its four nearest neighbors. The effect was to spatially smooth the frequency distribution parameters while leaving the mean values unchanged. The frequency distribution parameters were used to calculate the depth-duration-frequency (DDF) relation for each precipitation station. The ARC/INFO GRID function, POINTINTERP (Environmental Systems Research Institute, 1997) was used to interpolate surface grids of each DDF on a 2-km cell size. The interpolation was weighted by the number of years of record at each precipitation station. The result of this years-of-record weighting is that the final interpolated surface is closer to the observed values at stations having more years of record than at stations with less years of record. Interpolated-surface values from the 2-km cell corresponding to each precipitation station were determined for each station within Oklahoma. The values are included in the attribute tables. Related Data sets-- The set of 84 interpolated DDF surfaces and contours derived from each surface are being published with these data sets. Other References Cited-- Asquith, W.H., 1998, Depth-duration frequency of precipitation for Texas: U.S. Geological Survey Water-Resources Investigations Report 98-4044, 107 p. Environmental Systems Research Institute, Inc. (ESRI), 1997, ARC/INFO Command Reference, ARC/INFO Version 7.1.1 on-line help: Redlands, CA. Johnson, H.L., and Duchon, Claude E., 1995, Atlas of Oklahoma Climate: Norman, Okla., University of Oklahoma Press, 32 p. Tortorelli, R.L., Rea, Alan, and Asquith, W.H., 1999, Depth-duration frequency of precipitation for Oklahoma: U.S. Geological Survey Water-Resources Investigation Report (WRIR) 99-4232, 113 p. Notes-- Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, as well as in ARC/INFO format, this metadata file may include some ARC/INFO-specific terminology. 1999 Publication date Complete None Planned -103.83351898 -94.00019073 37.56702423 33.30012512 none Precipitation Frequency Analysis Precipitation Intensity Precipitation Sites inlandWaters none Oklahoma none These data are designed for regional analyses. Original precipitation-station locations were recorded to the nearest one minute of latitude and longitude. Alan Rea U.S. Geological Survey Hydrologist mailing and physical address

230 Collins Road

Boise Idaho 83702 USA 1-888-275-8747 (208)387-1372 (ahrea@usgs.gov) This data set was created under a cooperative agreement with the Oklahoma Department of Transportation. SunOS, 5.5.1, sun4u UNIX ARC/INFO version 7.2.1 The results of the error analysis for precipitation depth are described in the metadata for the surfaces data sets (surfaces.htm). Point features present. The data base of precipitation annual maxima was reviewed for questionable data, such as 1) very small values that usually indicate an incomplete year (commonly the first or last year of record), or 2) very large values that could not be verified. All data from the questionable year was removed from the data base for these cases. Another data base problem was discovered in the 15-minute data for which four stations had identical values in all three durations that matched the 1-hour value for all years of record. Records from those stations were removed from the data base. Removal of data from some years or stations did not greatly reduce the amount of precipitation data available from within and near Oklahoma. Station data were combined when two stations were within two minutes of longitude and/or latitude (about 2 miles). For example, occasionally an existing station is relocated to a nearby site, and new stations might be established near an existing station. If the distance between two stations is small, then the data were assumed equivalent and combined into a single data set. (similar to Asquith, 1998). Data sets were combined to increase the length of record of some nearby stations and to avoid potential problems in the analysis phase, which used 2-km grid cells to produce contour maps. Combined station records accounted for three stations having 15-minute data, 10 stations having hourly data and 18 stations having daily data. Only those stations that had at least 10 years of data were selected for this study to ensure that data were representative of long-term precipitation characteristics. Droughts or periods of abundant rainfall in Oklahoma characteristically extend for 3 to 5 years (Johnson and Duchon, 1995). The use of data with at least 10 years of record reduces the chance that data are unduly biased by climatic episodes. One station with eight years of 15-minute data was used for the analysis in an area where there was a sparsity of data. For more information see Tortorelli, Rea, and Asquith, 1999. Interpolated-surface values are given only for precipitation stations within Oklahoma. Locations of weather stations used in the depth-duration frequency analyses were recorded to the nearest 1 minute of latitude and longitude. First draft of metadata created by ahrea using FGDCMETA.AML ver. 1.33 07/15/99 on ARC/INFO data set /proj/temp1/okrain/cdproto/arc_data/7day/sites7d 19990726 Point Point 413 0.02 0.02 Decimal Degrees North American Datum of 1983 GRS1980 6378206.4 294.98 Each site data set is identified by its name and position in the directory structure. For example, the SITES7D data set in the 7day subdirectory contains precipitation-station data for the sites used for the 7-day duration. All depths are in inches. Data-set fields are defined, as in the following example, for the 7-day duration: > >SITES7D: > > FIELD NAME FIELD CONTENTS >AREA ARC/INFO Standard field >PERIMETER ARC/INFO Standard field >SITES7D# ARC/INFO Standard field >SITES7D-ID ARC/INFO Standard field >LONG Longitude, in decimal degrees (NAD83) >LAT Latitude, in decimal degrees (NAD83) >X-COORD X-Coordinate on Albers Equal Area projection (meters) >Y-COORD Y-Coordinate on Albers Equal Area projection (meters) >STAID Station ID >STANAME Station name >STATE State >YRSREC Years of record used in the analysis >FREQ2YR Calculated 2-year precipitation event (inches) >FREQ5YR Calculated 5-year precipitation event (inches) >FREQ10YR Calculated 10-year precipitation event (inches) >FREQ25YR Calculated 25-year precipitation event (inches) >FREQ50YR Calculated 50-year precipitation event (inches) >FREQ100YR Calculated 100-year precipitation event (inches) >FREQ500YR Calculated 500-year precipitation event (inches) >SURF2YR Interpolated value of 2-year precip event (inches) >SURF5YR Interpolated value of 5-year precip event (inches) >SURF10YR Interpolated value of 10-year precip event (inches) >SURF25YR Interpolated value of 25-year precip event (inches) >SURF50YR Interpolated value of 50-year precip event (inches) >SURF100YR Interpolated value of 100-year precip event (inches) >SURF500YR Interpolated value of 500-year precip event (inches) > > none U.S. Geological Survey Ask USGS - Water Webserver Team mailing

445 National Center

Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) http://water.usgs.gov/user_feedback_form.html Although this data set has been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data and related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Other ASCII file format zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_fnl_data.tar.gz Other ASCII file format zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_raw_data.tar.gz Other ARC/INFO workspaces zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_arc_12hour.tar.gz Other ARC/INFO workspaces zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_arc_15min.tar.gz Other ARC/INFO workspaces zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_arc_1day.tar.gz Other ARC/INFO workspaces zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_arc_1hour.tar.gz Other ARC/INFO workspaces zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_arc_24hour.tar.gz Other ARC/INFO workspaces zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_arc_2hour.tar.gz Other ARC/INFO workspaces zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_arc_30min.tar.gz Other ARC/INFO workspaces zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_arc_3day.tar.gz Other ARC/INFO workspaces zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_arc_3hour.tar.gz Other ARC/INFO workspaces zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_arc_60min.tar.gz Other ARC/INFO workspaces zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_arc_6hour.tar.gz Other ARC/INFO workspaces zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_arc_7day.tar.gz Other Nonproprietary file format zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_pd_12hour.tar.gz Other Nonproprietary file format zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_pd_15min.tar.gz Other Nonproprietary file format zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_pd_1day.tar.gz Other Nonproprietary file format zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_pd_1hour.tar.gz Other Nonproprietary file format zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_pd_24hour.tar.gz Other Nonproprietary file format zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_pd_2hour.tar.gz Other Nonproprietary file format zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_pd_30min.tar.gz Other Nonproprietary file format zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_pd_3day.tar.gz Other Nonproprietary file format zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_pd_3hour.tar.gz Other Nonproprietary file format zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_pd_60min.tar.gz Other Nonproprietary file format zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_pd_6hour.tar.gz Other Nonproprietary file format zipped 1 http://water.usgs.gov/GIS/dsdl/ofr99-463_pd_7day.tar.gz None. This dataset is provided by USGS as a public service. 20041108 U.S. Geological Survey Ask USGS -- Water Webserver Team mailing

445 National Center

Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) http://answers.usgs.gov/cgi-bin/gsanswers?pemail=h2oteam&subject=GIS+Dataset+ofr99-463_sites FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998