An assessment of the mesoscale variability of solar radiation at the earth's surface

Abstract

Based on a review of existing evidence of mesoscale variability in solar radiation at the earth's surface the conclusion is reached that significant variability does occur at this spatial scale but that full evaluation is hampered by the lack of long term observations. As a result a network designed specifically to evaluate these mesoscale variations is designed and implemented. Network design is based on an analysis of existing mesoscale data, mobile traverses with a pyranometer, and such considerations as a desire to assess the role of topography and urban impacts. The data collected over a 2.5 yr period from 12 stations located in Vancouver, B.C., Canada show that substantial spatial variability does occur even at the mesoscale. This variability is greatest under average conditions when partial cloud cover maximizes interstation differences. Seasonal variations in this pattern do occur and under clear summer skies the reduction in optical air mass with elevation is another contributor to spatial variability.