Water and Climate Program
Products and Services Briefing Book

PRISM Technology

PRISM is an analytical model that distributes point measurements of monthly, seasonal and annual precipitation to a geographic grid. The acronym PRISM stands for "Parameter-elevation Regressions on Independent Slopes Model." PRISM can generate both raster and vector estimates of precipitation at a resolution of 2 kilometers by 2 kilometers. PRISM uses a digital elevation model (DEM) that contains information describing the earth's topography (slopes, aspects, elevations) and observed precipitation measurements to determine variations in precipitation as functions of elevations. Orographic precipitation and rain shadows are modeled in PRISM in a unique and accurate way.

PRISM-derived products are produced in a GIS-compatible latitude-longitude grid or a gridded map projection such as Albers Equal Area (AEA) at national, state and county scales. Oregon State University, through the Oregon Climate Service, is performing the work under a cooperative agreement with the Natural Resources Conservation Service National Water and Climate Center. Digital layers will be available from the National Cartographic and Geospatial Center by mid-1997.