Landscape insolation modeler. Johnson, Kipp¹, Harris, Norman^*,2, Louhaichi, Mounir¹, Johnson, Michael¹, George, Melvin³, ¹ Department of Rangeland Resources, Corvallis, OR, USA² Palmer Research Center, Palmer, AK, USA³ Department of Agronomy and Range Science, Davis, CA, USA

ABSTRACT- Plants and animals live and grow in a fluctuating energy environment that controls their expression and defines their range. Incoming solar radiation varies predictably across the earth with superimposed topographic, climatic, and atmospheric variation. We developed a computer program, the Insolation Modeler that estimates the intensity of solar insolation due to direct sunlight and incoming diffuse radiation based on site location, time, and a digital elevation model of the area of interest. While this program was made for the purpose of determining landscape-wide suitability for animal use in the Kress Modeler, it can also be used independently for any project interested in determining the incoming solar radiation and the effects of land contour and geographic position. Users input a digital elevation model (DEM) in ASCII raster format which the program uses to determine when a location will be exposed to direct sunlight and when it will be in shadow based on the contour of the ground and the time and date of interest. The program then calculates solar position for the time interval and time step of interest. Slope and aspect of all grid cells in the DEM are calculated so that angle of incidence for each sun position can be determined. For each time step, direct, diffuse and global insolation is calculated for a user supplied solar constant and atmospheric transmission coefficient. The Insolation Modeler produces ASCII raster maps, one for each time step, with insolation in Watts⋅m^-2. Insolation models should help ecologist explain plant and animal distributions on landscapes.

KEY WORDS: Landscape, Insolation, DEM, Solar