Potential evapotranspiration and climate in Alaska by Thornthwaite's Classification
Document Type: Report
Author(s): James H. Patric; Peter E. Black
Publication Year: 1968

Cataloging Information

  • Barrow
  • Canada
  • evaporative demand
  • Northwest Territories
  • Palmer
  • potential evapotranspiration
  • precipitation
  • stream-gaging
  • Thornwaite
  • United States Weather Bureau
  • US Geological Survey
Record Maintained By:
Record Last Modified: December 3, 2015
FRAMES Record Number: 6099


From introduction: 'Long ago, Fernow wrote concerning 'the desirability of utilizing the Weather Bureau, the various agricultural experiment stations, and other forces, in forming a systematic service of water stations, and in making a careful survey of the conditions of water supplies, which may serve as a basis for the application of rational principles of water management.' Over the intervening years, many of these statistics have been amassed for other States, but many still are unavailable of Alaska. This report is a step for Alaska along the path pointed out by Fernow. Although Alaska currently has about 200 climatological stations, it has only 0.03 rain gage per 100 square miles, or about one-tenth the gage density for conterminous United States. This density is inadequate for realistic maps of precipitation, temperature, or runoff. Nevertheless, the U.S. Weather Bureau is accumulating a large and growing record of precipitation and temperature of the State, and the U.S. Geological Survey heads an expanding stream-gaging program. There has been less attention to evaporative losses which determine differences between precipitation income and water available for human needs. As Thornthwaite (1948) pointed out, wet and dry climates are determined neither by total nor seasonal precipitation but by the relation of precipitation to the evaporative demand. For example, precipitation amounts are nearly equal in California's Mojave Desert and in Alaska's forested and frequently boggy interior. The important and often overlooked difference between climates of these regions is the amount and timing of the evaporative demand -- over 100 inches per yearlong in the Mojave; only about one-sixth as much during summer in Alaska's interior.'

Patric, James H.; Black, Peter E. 1968. Potential evapotranspiration and climate in Alaska by Thornthwaite's Classification. Research Paper. PNW-71. USDA Forest Service, Pacific Northwest Forest and Range Experiment Station. Juneau, Alaska. 28 pp.