ak_precip is a polygon coverage created from a 1:2000000 scale map showing
lines of equal annual precipitation in Alaska. The precipitation map was
prepared in 1994 as part of a flood frequency study of the streams and rivers
of Alaska and was digitized into a GIS format. Precipitation values for
polygons were set to equal the average value of their bounding lines of equal
annual precipitation.
The original purpose of the precipitation map of Alaska was to provide precipitation values for use in computing flood peaks and their associated recurrence intervals at ungaged rivers and streams in Alaska. Realizing other uses of the precipitation map and the need for a digital product, the precipitation map was converted to a digital format.
Procedures_Used:
The original precipitation map was done on a 1:2,000,000 scale map of Alaska. The isolines were digitized from the mylar and entered into ARC-INFO. In ARC-EDIT, the isolines were joined with an outline of Alaska (1:250,000 scale to create the digitized precipitation map. The amount of precipitation for each polygon was determined to be the average value between bounding isolines.
Revisions:
This precipitation map of Alaska represents the most current version (1994). As more data and/or new techniques become available, the map will be updated. In 1998, there were no plans to update the map.
Reviews_Applied_to_Data:
Reviews of the digitized data were done by Emily Binnian, Stan Jones, Tim Brabets, Ben Kennedy, and Roy Glass. A review of the documentation was done by Roy Glass. Editorial review of the documentation was done Liska Snyder.
Related_Spatial_and_Tabular_Data_Sets:
None
Other_References_Cited:
Jones, S.H., and Fahl, C.B., 1994, Magnitude and frequency of floods in Alaska and conterminous basins of Canada: U.S. Geological Survey Water-Resources Investigations Report 93-4179, 122 p., 2 plates.
Notes:
None
None
None planned
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Point_of_Contact USGS-WRD
The precipitation map was developed using a relatively small number of precipitation stations and the map has large intervals between contours of equal annual precipitation. Thus, caution should be used when interpreting precipitation values. The original map was prepared on a 1:2,000,000 scale. Thus, scales smaller than this should be used with caution.
Stan Jones, Charlie Fahl, Emily Binnian, Ben Kennedy, Roy Glass.
Unknown
Unknown
The standard items are included in the polygon attribute table along with one additional item: INCHES, which is the amount of annual precipitation, in inches, for a given area.