I have a research site in Mendocino County, California where I have taken several months of insolation measurements using two Hukseflux LP02 black body Pyranometers. One is equiped with a shade ring. Measurements were taken in an open field with no topographic shading. Surrounding area is hilly and forested.
I have run r.sun for every week of the year, and compared the values that match my measurement times. The global radiation values match within 5%. However, the ratio of direct to diffuse radiation is off. r.sun is reporting 20-22% diffuse radiation, while the field measurements are reporting 7-10% diffuse. I am using Linke Turbidity Index values from www.helioclim.org, which look too high. However, when I tried arbitrarily changing the Linke Turbidity index and rerunning r.sun, I could get the diffuse/direct ratio to match field values, but then the global radiation was much too high. Am I missing a parameter to help with this? Any suggestions would be appreciated. Collin _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
