92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Monday, 23 January 2012
Air Quality and Visibility in Southwestern British Columbia During Forest Fire Smoke Events
Hall E (New Orleans Convention Center )
Jenna C. Keane, Univ. of British Columbia, Vancouver, BC, Canada; and I. McKendry and A. Teakles

In recent years, the frequency of forest fires has been increasing in western North America. With an increase in forest fire activity, attention has been drawn to the negative effects forest fire smoke has on air quality and visibility. Smoke particles from forest fires can travel over long distances, degrading air quality. This study quantifies the relationship between smoke, air quality and visibility. Furthermore, determining how smoke produced by forest fires influences air quality and visibility in southwestern British Columbia will improve air quality forecasting. The study was conducted from 2007 through 2011 during the fire season (April through October) in southwestern British Columbia, focusing on the Georgia Basin airshed.

A host of tools were used to determine how air quality and visibility are influenced by forest fire smoke. Satellite Fire Detection from National Oceanic and Atmospheric Administration's (NOAA), National Geophysical Data Center (NGDC) was used to determine on which days during the five year period smoke was present in southwestern British Columbia. To determine where smoke particles were transported from, NOAA's HYbrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used. Backward trajectories were computed from Vancouver International Airport (YVR) on days which smoke was present. PM2.5 (particles with a diameter of less than 2.5 microns) and ozone concentrations were examined at thirteen different locations. Gases and aerosols produced by forest fires are known to degrade visibility. A semi-automated approach was used to calculate visibility using digital images. Free online software, ImageJ, was used to register the images, and calculate intensity. Image metrics were a large part of calculating visibility. Image registration was done to correct for camera movement. Once the images were corrected, contrast and visibility were calculated. Two dark objects in the background were used to calculate visibility. A viewshed analysis was done in ArcGIS to calculate the distance from the camera to the chosen targets.

Southwestern British Columbia's air quality and visibility is negatively influenced by forest fire smoke. From HYSPLIT it was found that smoke seen in southwestern British Columbia was usually transported from the United States or Alberta. Smoke and aerosol concentrations in the region were largely influenced by the dominating weather pattern. For example during a stagnant high pressure system in the summer months air quality was significant degraded. Furthermore, the concentrations of particulate matter and ozone increased when smoke was present. Calculating visibility using digital images is a low cost method that can be used in the future. The conclusions drawn from this research help improve regional air quality and visibility forecasts.

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