Landfalling atmospheric rivers (ARs) frequently trigger heavy and sometimes prolonged precipitati... more Landfalling atmospheric rivers (ARs) frequently trigger heavy and sometimes prolonged precipitation, especially in regions with favored orographic enhancement. The presence and strength of ARs are ...
Biomass burning emissions emit a significant amount of trace gases and aerosols and can affect at... more Biomass burning emissions emit a significant amount of trace gases and aerosols and can affect atmospheric chemistry and radiative forcing for hundreds or thousands of kilometres downwind. They can also contribute to exceedances of air quality standards and have negative impacts on human health. We present a case study of an intense wildfire plume from Siberia that affected the air quality across the Pacific Northwest on 6-10 July 2012. Using satellite measurements (MODIS True Colour RGB imagery and MODIS AOD), we track the wildfire smoke plume from its origin in Siberia to the Pacific Northwest where subsidence ahead of a subtropical Pacific High made the plume settle over the region. The normalized enhancement ratios of O 3 and PM 1 relative to CO of 0.26 and 0.08 are consistent with a plume aged 6-10 days. The aerosol mass in the plume was mainly submicron in diameter (PM 1 / PM 2.5 = 0.96) and the part of the plume sampled at the Whistler High Elevation Monitoring Site (2182 m a.s.l.) was 88 % organic material. Stable atmospheric conditions along the coast limited the initial entrainment of the plume and caused local anthropogenic emissions to build up. A synthesis of air quality from the regional surface monitoring networks describes changes in ambient O 3 and PM 2.5 during the event and contrasts them to baseline air quality estimates from the AURAMS chemical transport model without wildfire emissions. Overall, the smoke plume contributed significantly to the exceedances in O 3 and PM 2.5 air quality standards and objectives that occurred at several communities in the region during the event. Peak enhancements in 8 h O 3 of 34-44 ppbv and 24 h PM 2.5 of 10-32 µg m −3 were attributed to the effects of the smoke plume across the Interior of British Columbia and at the Whistler Peak High Elevation Site. Lesser enhancements of 10-12 ppbv for 8 h O 3 and of 4-9 µg m −3 for 24 h PM 2.5 occurred across coastal British Columbia and Washington State. The findings suggest that the large air quality impacts seen during this event were a combination of the efficient transport of the plume across the Pacific, favourable entrainment conditions across the BC interior, and the large scale of the Siberian wildfire emissions. A warming climate increases the risk of increased wildfire activity and events of this scale reoccurring under appropriate meteorological conditions.
Journal of the Air & Waste Management Association (1995), 2018
Visibility degradation, one of the most noticeable indicators of poor air quality, can occur desp... more Visibility degradation, one of the most noticeable indicators of poor air quality, can occur despite relatively low levels of particulate matter when the risk to human health is low. The availability of timely and reliable visibility forecasts can provide a more comprehensive understanding of the anticipated air quality conditions to better inform local jurisdictions and the public. This paper describes the development of a visibility forecasting modeling framework, which leverages the existing air quality and meteorological forecasts from Canada's operational Regional Air Quality Deterministic Prediction System (RAQDPS) for the Lower Fraser Valley of British Columbia. A baseline model (GM-IMPROVE) was constructed using the revised IMPROVE algorithm based on unprocessed forecasts from the RAQDPS. Three additional prototypes (UMOS-HYB, GM-MLR, GM-RF) were also developed and assessed for forecast performance of up to 48 hr lead time during various air quality and meteorological co...
Landfalling atmospheric rivers (ARs) frequently trigger heavy and sometimes prolonged precipitati... more Landfalling atmospheric rivers (ARs) frequently trigger heavy and sometimes prolonged precipitation, especially in regions with significant orography. The presence and strength of ARs are often des...
Weekly NH 3 emissions in 4 Â 4 km grid cells during and after a major poultry cull. Concentration... more Weekly NH 3 emissions in 4 Â 4 km grid cells during and after a major poultry cull. Concentrations NH 3 were measured at 2 locations outside and 1 inside the cull area. Wide variation in emissions due to farm activities and weather factors. Good correlation between emission estimates and ambient measurements. Detailed inventories useful for policy decisions and improving model inputs.
Journal of the Air & Waste Management Association, 2015
Fine particulate matter (PM 2.5 ) is the dominant cause of atmospheric visibility degradation in ... more Fine particulate matter (PM 2.5 ) is the dominant cause of atmospheric visibility degradation in the Lower Fraser Valley (LFV) of British Columbia, where poor visibility due to air pollution is of concern. The spatial coverage of the current LFV visibility monitoring network is relatively low, with large parts of the airshed not being represented. Given the desire on the part of local and regional governments to manage visibility in the LFV airshed, the development of a method that allows near real-time estimation of 1-hr light extinction data from the dense network of PM measurements would be highly beneficial. This paper describes a simple linear algorithm, developed using the Hybrid method, to estimate near real-time 1-hr total light extinction at four monitoring sites in the LFV. Model inputs include ambient hourly PM 2.5 , NO 2 , relative humidity measurements, and historical monthly-averaged aerosol composition. The results indicate that the developed model can provide relatively accurate and time-resolved estimates of extinction in regions where visibility is not being monitored, thus extending the spatial coverage of the regional visibility monitoring network. The model was also applied to a number of policy-related scenarios to inform visual air quality management in the study area. Results indicated that in order to achieve a perceptible improvement (1.0 deciview) relative to baseline average visibility conditions in the LFV airshed, average ambient PM 2.5 concentration would have to decrease by 17% from baseline conditions. Furthermore, to achieve a 20% increase in the number of daylight hours with "excellent" visibility, average PM 2.5 would need to be reduced by 30%. Model simulations also indicated that "across-theboard" emission reduction policies would result in greater improvements for the "worst 20%" visibility conditions than for the "best 20%" conditions, suggesting that reducing the number of "poor" visibility days would be easier than improving the number of "excellent" visibility days.
Landfalling atmospheric rivers (ARs) frequently trigger heavy and sometimes prolonged precipitati... more Landfalling atmospheric rivers (ARs) frequently trigger heavy and sometimes prolonged precipitation, especially in regions with favored orographic enhancement. The presence and strength of ARs are ...
Biomass burning emissions emit a significant amount of trace gases and aerosols and can affect at... more Biomass burning emissions emit a significant amount of trace gases and aerosols and can affect atmospheric chemistry and radiative forcing for hundreds or thousands of kilometres downwind. They can also contribute to exceedances of air quality standards and have negative impacts on human health. We present a case study of an intense wildfire plume from Siberia that affected the air quality across the Pacific Northwest on 6-10 July 2012. Using satellite measurements (MODIS True Colour RGB imagery and MODIS AOD), we track the wildfire smoke plume from its origin in Siberia to the Pacific Northwest where subsidence ahead of a subtropical Pacific High made the plume settle over the region. The normalized enhancement ratios of O 3 and PM 1 relative to CO of 0.26 and 0.08 are consistent with a plume aged 6-10 days. The aerosol mass in the plume was mainly submicron in diameter (PM 1 / PM 2.5 = 0.96) and the part of the plume sampled at the Whistler High Elevation Monitoring Site (2182 m a.s.l.) was 88 % organic material. Stable atmospheric conditions along the coast limited the initial entrainment of the plume and caused local anthropogenic emissions to build up. A synthesis of air quality from the regional surface monitoring networks describes changes in ambient O 3 and PM 2.5 during the event and contrasts them to baseline air quality estimates from the AURAMS chemical transport model without wildfire emissions. Overall, the smoke plume contributed significantly to the exceedances in O 3 and PM 2.5 air quality standards and objectives that occurred at several communities in the region during the event. Peak enhancements in 8 h O 3 of 34-44 ppbv and 24 h PM 2.5 of 10-32 µg m −3 were attributed to the effects of the smoke plume across the Interior of British Columbia and at the Whistler Peak High Elevation Site. Lesser enhancements of 10-12 ppbv for 8 h O 3 and of 4-9 µg m −3 for 24 h PM 2.5 occurred across coastal British Columbia and Washington State. The findings suggest that the large air quality impacts seen during this event were a combination of the efficient transport of the plume across the Pacific, favourable entrainment conditions across the BC interior, and the large scale of the Siberian wildfire emissions. A warming climate increases the risk of increased wildfire activity and events of this scale reoccurring under appropriate meteorological conditions.
Journal of the Air & Waste Management Association (1995), 2018
Visibility degradation, one of the most noticeable indicators of poor air quality, can occur desp... more Visibility degradation, one of the most noticeable indicators of poor air quality, can occur despite relatively low levels of particulate matter when the risk to human health is low. The availability of timely and reliable visibility forecasts can provide a more comprehensive understanding of the anticipated air quality conditions to better inform local jurisdictions and the public. This paper describes the development of a visibility forecasting modeling framework, which leverages the existing air quality and meteorological forecasts from Canada's operational Regional Air Quality Deterministic Prediction System (RAQDPS) for the Lower Fraser Valley of British Columbia. A baseline model (GM-IMPROVE) was constructed using the revised IMPROVE algorithm based on unprocessed forecasts from the RAQDPS. Three additional prototypes (UMOS-HYB, GM-MLR, GM-RF) were also developed and assessed for forecast performance of up to 48 hr lead time during various air quality and meteorological co...
Landfalling atmospheric rivers (ARs) frequently trigger heavy and sometimes prolonged precipitati... more Landfalling atmospheric rivers (ARs) frequently trigger heavy and sometimes prolonged precipitation, especially in regions with significant orography. The presence and strength of ARs are often des...
Weekly NH 3 emissions in 4 Â 4 km grid cells during and after a major poultry cull. Concentration... more Weekly NH 3 emissions in 4 Â 4 km grid cells during and after a major poultry cull. Concentrations NH 3 were measured at 2 locations outside and 1 inside the cull area. Wide variation in emissions due to farm activities and weather factors. Good correlation between emission estimates and ambient measurements. Detailed inventories useful for policy decisions and improving model inputs.
Journal of the Air & Waste Management Association, 2015
Fine particulate matter (PM 2.5 ) is the dominant cause of atmospheric visibility degradation in ... more Fine particulate matter (PM 2.5 ) is the dominant cause of atmospheric visibility degradation in the Lower Fraser Valley (LFV) of British Columbia, where poor visibility due to air pollution is of concern. The spatial coverage of the current LFV visibility monitoring network is relatively low, with large parts of the airshed not being represented. Given the desire on the part of local and regional governments to manage visibility in the LFV airshed, the development of a method that allows near real-time estimation of 1-hr light extinction data from the dense network of PM measurements would be highly beneficial. This paper describes a simple linear algorithm, developed using the Hybrid method, to estimate near real-time 1-hr total light extinction at four monitoring sites in the LFV. Model inputs include ambient hourly PM 2.5 , NO 2 , relative humidity measurements, and historical monthly-averaged aerosol composition. The results indicate that the developed model can provide relatively accurate and time-resolved estimates of extinction in regions where visibility is not being monitored, thus extending the spatial coverage of the regional visibility monitoring network. The model was also applied to a number of policy-related scenarios to inform visual air quality management in the study area. Results indicated that in order to achieve a perceptible improvement (1.0 deciview) relative to baseline average visibility conditions in the LFV airshed, average ambient PM 2.5 concentration would have to decrease by 17% from baseline conditions. Furthermore, to achieve a 20% increase in the number of daylight hours with "excellent" visibility, average PM 2.5 would need to be reduced by 30%. Model simulations also indicated that "across-theboard" emission reduction policies would result in greater improvements for the "worst 20%" visibility conditions than for the "best 20%" conditions, suggesting that reducing the number of "poor" visibility days would be easier than improving the number of "excellent" visibility days.
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Papers by Rita So