Annual Precipitation of Washington, USA from 1981-2010

This isarithmic map uses PRISM (Parameter-elevation Regressions on Independent Slopes Model) derived data to showcase the annual precipitation of Washington state, USA over a ~30 year period (1981-2010). Originally created by the PRISM Group at Oregon State University, the PRISM system has proved to be a leading system in producing quality precipitation maps. A climate-elevation regression function is calculated in PRISM with consideration of climate variables that may influence the data, such as proximity to coast, atmospheric layer, topography of region, and more. As precipitation tends to increase with elevation, elevation is an included variable in PRISM using a digital elevation model (DEM) and each DEM grid cell has its own climate-elevation regression function calculated within.