Digital Data Sets of Depth-Duration Frequency of Precipitation for Oklahoma, USGS OFR 99-463.

These geospatial data sets consist of contours
derived from surface grids of precipitation depths for
seven frequencies at 12 durations used in a regional
precipitation frequency analysis for Oklahoma. Eighty-four
depth-duration-frequency contour maps were produced from
precipitation-station data. The contour interval varies from
0.05 to 0.5 inch.

Data were used from precipitation gage stations with at least 10
years of record within Oklahoma and about 50 kilometers into
bordering states. 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).

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.