Electronic sun journal as an evaluation tool for measuring sunflecks while walking through urban forests

Electronic sun journal as an evaluation tool for measuring sunflecks while walking through urban forests

Fluctuations in direct sunlight intensities (or sunflecks) are experienced in urban forest parklands. A novel application of an electronic sun journal (ESJ) was developed providing accessible, objective detection and analysis of sunflecks sampled at 50 Hz while walking through urban parkland forests in Toowoomba (27.57°S 151.95°E), Australia. A total of 654 sunflecks were detected during 12 walks. Sunfleck durations (SFD) ranged from 0.02 s to 102.5 s, with a median of 0.10 s and interquartile range of 0.04-0.28 s. The sunfleck intervals (SFI) ranged from 0.02 s to 115 s, with a median of 0.16 s and interquartile range of 0.06-0.62 s. Of the 10,983 sunfleck clusters, approximately 90% included two or four sunflecks per second, with the highest frequency cluster reaching eight. The distribution of the sunfleck clusters changed with different sun angles and azimuth as the sunlight passed through different parts of urban parklands. The developed method with the ESJ may be employed in the evaluation of sunfleck durations, intervals and clusters at eye level in other urban forest environments, adding to the developing interest as greenspaces play an increasing role in urban studies.