Open Collections

Application of the urban airshed model in the Lower Fraser Valley, British Columbia

University of British Columbia

The Lower Fraser Valley (LFV) of outhwestern British Columbia is periodically subject to unacceptably high concentrations of ground-level ozone (O₃). To investigate the factors which influence elevated 0₃ concentrations in the LFV, a three-dimensional Eulerian model called the Urban Airshed Model was used to simulate an historical O₃episode which occurred between July 17-19, 1985. The results showed generally satisfactory model performance for predicted O₃ levels across the region, relative to model performance parameters established elsewhere. Peak unpaired accuracies ranged from -2% to -24% and normalized gross error ranged from 35.6-36.9% over the three-day simulation. However, there was a tendency for the model to underestimate O₃concentrations, as reflected in the normalized bias, which ranged from -29.1 to -31.3%. Spatial patterns of predicted O₃concentrations indicated that higher O₃concentrations were observed along the valley walls and tributary valleys than on the valley floor where most of the population resides. Overall model performance based on nitrogen dioxide levels was within established parameters, although concentrations were typically underestimated and performance at two stations was poor. As a further means of assessing model performance, 0three indicator species (NOy, 0₃/NOz and H₂O₂/HNO₃) were calculated to determine the ozone sensitivity of the modelled airshed. The findings suggest that with the exception of sites located far downwind of the major source region, conditions tended to be VOC-limited.

Thesis/Dissertation

application/pdf

2009-03-24

For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.

http://hdl.handle.net/2429/6440

Atmospheric Science

University of British Columbia

UBCV

DSpace