Related Experiment Videos
Estimation of pedestrian level UV exposure under trees
Richard H Grant1, Gordon M Heisler, Wei Gao
1Department of Agronomy, Purdue University, W. Lafayette, IN 47907-1150, USA. rgrant@purdue.edu
Photochemistry and Photobiology
|May 11, 2002
Summary
Trees significantly impact pedestrian sun exposure. Even shady spots can have substantial ultraviolet-B (UV-B) radiation, but 90% tree cover offers substantial protection (UPF 10) across latitudes.
Area of Science:
- Environmental Science
- Atmospheric Science
- Public Health
Background:
- Solar ultraviolet radiation (UV-B) poses health risks to pedestrians.
- Urban trees modify UV-B irradiance, but quantitative data in open canopies is limited.
- Understanding UV-B exposure under tree canopies is crucial for public health strategies.
Purpose of the Study:
- To develop and validate a model predicting UV-B irradiance in open-tree canopies.
- To assess pedestrian UV-B exposure in relation to tree cover and latitude.
- To determine the effectiveness of tree cover in providing ultraviolet protection factors (UPF).
Main Methods:
- A three-dimensional model was created to simulate UV-B irradiance fields in open-tree canopies.
- Model predictions were validated against measurements under clear skies.
- Simulations assessed UV-B exposure for different tree cover percentages and latitudes.
Main Results:
- The model accurately predicted relative UV-B irradiance (MBE < 0.01, RMSE = 0.07).
- Shady locations can receive significant UV-B exposure (40-60% of direct sunlight).
- 90% tree cover provides a UPF of 10 across latitudes (15-60 degrees); <50% cover offers UPF < 2.
Conclusions:
- Urban trees significantly modulate pedestrian UV-B exposure.
- Even areas perceived as shady require careful consideration for UV protection.
- High tree cover (90%) is highly effective in mitigating UV-B exposure, offering substantial UPF.