DIGITAL-MAP GRIDS OF MEAN-ANNUAL PRECIPITATION FOR 1961-90, AND GENERALIZED SKEW COEFFICIENTS OF ANNUAL MAXIMUM STREAMFLOW FOR OKLAHOMA

U.S. Geological Survey Open-File Report 97-574

Prepared in cooperation with the
**Oklahoma Department of Transportation**

Oklahoma City, Oklahoma

1997

Introduction

File formats

Data Organization

Geometric Registration

Notes

References Cited

The second data set is a grid of generalized skew coefficients of logarithms of annual maximum streamflow for Oklahoma streams less than or equal to 2,510 square miles in drainage area. This grid of skew coefficients is taken from figure 11 of Tortorelli and Bergman, 1985, "Techniques for estimating flood peak discharges for unregulated streams and streams regulated by small floodwater retarding structures in Oklahoma," U.S. Geological Survey Water-Resources Investigations Report 84-4358. To save disk space, the skew coefficient values have been multiplied by 100 and rounded to integers with two significant digits. The data sets are provided in an ASCII grid format.

The second data set is a grid of generalized skew coefficients
of
logarithms of annual maximum streamflow for Oklahoma streams less than
or equal to 2,510 square miles in drainage area. This grid of skew
coefficients is taken from figure 11 of Tortorelli and
Bergman, (1985). To save disk space, the skew coefficient values have

The U.S. Geological Survey compiled these data sets in cooperation with the Oklahoma Department of Transportation.

The "SKEWGRID.ASC" file is compressed with the GZIP utility.
The GUNZIP
utility is an MS-DOS executable program that will
uncompress the data file. The file should first be copied to hard disk.
To uncompress the file, type at the MS-DOS prompt:
```
GUNZIP -aN SKEWGRID.GZ
```

This will uncompress the file and restore its original name, "SKEWGRID.ASC".

The documentation files comply with the Federal Geographic Data Committee (FGDC) Content Standards for Digital Geospatial Metadata (Federal Geographic Data Committee, 1994). The FGDC-compliant metadata files contain detailed descriptions of the data sets, and include narrative sections describing the procedures used to produce the data sets in digital form.

A graphic image also is provided in a Graphics Interchange Format (GIF) file. GIF files are easily displayed on a variety of computer systems using readily available display software. This image provides a simplified view of the data sets, and may be used for browsing purposes. The GIF file portrays significantly less spatial resolution and information content than the actual data sets.

- A_NOTICE.TXT
- Liability disclaimer
- PRECIP.GIF
- A GIF image of an illustration from Tortorelli (1997) showing lines of equal mean annual precipitation, in inches, for 1961-90
- MAPRECIP.ASC
- Mean Annual Precipitation ASCII grid, in inches
- MAPRECIP.PRJ
- Map-projection parameters for the mean annual precipitation data set
- MAPRECIP.HTML
- Complete documentation of the data sources and procedures used to create the mean annual precipitation grid
- SKEW.GIF
- A GIF image of an illustration from Tortorelli (1997) showing lines of equal generalized peak skew coefficients
- SKEWGRID.GZ
- Generalized peak skew coefficients ASCII grid, multiplied by 100 and rounded to two significant digits (Compressed with GZIP)
- SKEWGRID.PRJ
- Map-projection parameters for the generalized peak skew coefficients data set
- SKEWGRID.HTML
- Complete documentation of the data sources and procedures used to create the generalized peak skew coefficients data set

This projection slightly distorts shapes and distances (scale) in order to maintain equal-area properties. Scale is true along the standard parallels (Snyder, 1987).

Albers Equal Area projection parameters

[GRS1980, Geodetic Reference System; 1980 NAD83, North American Datum 1983]

Projection parameters: | |
---|---|

Spheroid | GRS1980 |

Datum | NAD83 |

First standard parallel | 34 00 00 North |

Second standard parallel | 36 30 00 North |

Central meridian | 98 00 00 West |

Latitude of projection origin | 33 00 00 North |

Coordinate system parameters: | |

False easting | 0 |

False northing | 0 |

Planimetric units of measure | meters |

The data sets were processed using the ARC/INFO Revision 7.0.3 software package, running on a Data General AViiON workstation. File names, directories, and pathnames in this document are enclosed in quotation marks, and type set in upper case. Pathnames use MS-DOS-style naming conventions, with the "\" character indicating the highest-level directory of the diskette.

Daly, C., R.P. Neilson, and D.L. Phillips, 1994, A statistical- topographic model for mapping climatological precipitation over mountainous terrain: Journal of Applied Meteorology, v. 33, no. 2, p. 140-158. Federal Geographic Data Committee, 1994, Content standards for digital geospatial metadata (June 8): Federal Geographic Data Committee, Washington, D.C., 78 p.

Snyder, J.P., 1987, Map projections--A working manual: U.S. Geological Survey Professional Paper 1395, 383 p.

Tortorelli, R.L., 1997, Techniques for estimating peak-streamflow frequency for unregulated streams and streams regulated by small floodwater retarding structures in Oklahoma: U.S. Geological Survey Water-Resources Investigations Report 97-4202, 39 p.

Tortorelli, R.L., and Bergman, D.L., 1985, Techniques for estimating
flood peak discharges for unregulated streams
and streams
regulated by small floodwater retarding structures
in Oklahoma:
U.S. Geological Survey Water-Resources Investigations
Report
84-4358, 85 p.

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