Spatial variability and interpolation of stochastic weather simulation model parameters

The spatial variability of 58 precipitation and temperature parameters from the "generation of weather elements for multiple applications" (GEM) weath er generator has been investigated over a region of significant complexity in topography and climate. GEM parameters were derived for 80 climate stati ons in southern Idaho and southeastern Oregon. A technique was developed an d used to determine the GEM parameters from high-elevation snowpack telemet ry stations that report precipitation in nonstandard 2.5-mm (versus 0.25 mm ) increments. Important dependencies were noted between most of these param eters and elevation (both domainwide and local), location, and other factor s. The "parameter-elevation regressions on independent slopes model" (PRISM ) spatial modeling system was used to develop approximate 4-km gridded data fields of each of these parameters. A feature was developed in PRISM that models temperatures above and below mean inversions differently. Examples o f the spatial fields derived from this study and a discussion of the applic ations of these spatial parameter fields are included.