Annual Precipitation layer

The Annual Precipitation layer shows the average amount of water (rain, snow, hail, etc...) that falls at a given location in a year.

Annual precipitation in Idaho Annual precipitation in northern New Mexico

Details

This layer has no detail -- just the amount (in millimeters or inches).

Options

Transparency

Determines how much the underlying layer(s) will show through this layer.

Colors

  • Normal: use the standard palette
  • None: only show the outline of the zones

Border color

Defines the color used to draw the zone outlines

Origin

George Taylor, the Oregon Climate Service at Oregon State University
United States Average Annual Precipitation, 1961-1990

This data is available directly from the National Atlas.

Description of data source

Abstract

This map layer shows polygons of average annual precipitation in the contiguous United States, for the climatological period 1961-1990. Parameter-elevation Regressions on Independent Slopes Model (PRISM) derived raster data is the underlying data set from which the polygons and vectors were created. PRISM is an analytical model that uses point data and a digital elevation model (DEM) to generate gridded estimates of annual, monthly and event-based climatic parameters.

Purpose

These data are intended for geographic display and analysis at the national level, and for large regional areas. The data should be displayed and analyzed at scales appropriate for 1:2,000,000-scale data. No responsibility is assumed by the Spatial Climate Analysis Service, the USDA - NRCS National Water and Climate Center, the USDA - NRCS National Cartography and Geospatial Center, or the U.S. Geological Survey in the use of these data.

Supplemental Information

There are many methods of interpolating precipitation from monitoring stations to grid points. Some provide estimates of acceptable accuracy in flat terrain, but few have been able to adequately explain the extreme, complex variations in precipitation that occur in mountainous regions. Significant progress in this area has been achieved through the development of PRISM (Parameter-elevation Regressions on Independent Slopes Model). PRISM is an analytical model that uses point data and a digital elevation model (DEM) to generate gridded estimates of monthly and annual precipitation (as well as other climatic parameters). PRISM is well suited to regions with mountainous terrain, because it incorporates a conceptual framework that addresses the spatial scale and pattern of precipitation in such regions.