Forecasting Methodology

by Ron Hartling

In the absence of any authoritative source of PM2.5 forecasts for the Kingston area, I gradually learned to base my forecasts on combining Environment Canada daily wind direction forecasts with the broader continental wind and air pollution flows displayed in the real-time satellite imagery which you can view on this site’s Home page. During wildfire season, I also factor in the UBC Firesmoke model. I then correlate the data from those sources intuitively based on how similar patterns actually turned out in the next day’s readings. While prediction of the exact readings proved impossible, my best guesses have fairly reliably predicted the magnitude and approximate timing of increasing and decreasing air quality trends, which is what one really needs to know in order to be able to take effective precautions.

Based on analysis of the most recent five years of Kingston hourly PM2.5 readings compared to Environment Canada data on measured hourly wind directions and speeds, I found a strong correlation with wind direction. As you  can see from the Evidence page, I then undertook analysis which demonstrated little or no correlation between actual PM2.5 readings and  weekends versus weekdays or overnight versus working hours, thereby establishing that Kingston’s airborne particulate pollution is almost exclusively caused by emissions from other jurisdictions rather than from any local sources. Kingston PM2.5 readings rise significantly whenever winds from the south and southeast are bringing us particulates from the highly-industrialized United States, especially from the Texas/Louisiana oil refinery belt where most of the continent’s fossil fuels are processed.  During wildfire season, the impact of other wind directions depends on the current location of major smoke clouds, both from Canada and the southern USA.

The satellite app allows for clicking on any point in the map to view its current PM2.5 readings, which makes easy to estimate the severity of incoming polluted airmasses.

There is a further complication in the correlation between Environment Canada’s wind-direction forecasts for the Kingston area and the observed arrival of PM2.5 particulate clouds, which mostly originate in the United States. While that forecast includes quite variable local wind conditions, the overarching Jetstream appears to be a more accurate predictor of when and if those clouds actually pass over or near Kingston.

The cause-and-effect relationship between those three sources is situation-dependent, given that winds can only blow what particulates are or are not present in the air masses which happen to be passing overhead.  In order to make that information useful for personal decision-making, I attempt to encapsulate it into a one-line forecast summary based on what experience suggests is the most likely outcome of the juxtaposition of those three factors into a forecast risk level (0, 1, 2, etc.) for the next day. I consider anything under the evidence-based WHO annual average daily exposure limit of 5 µg/m3 to be reasonably healthy and therefore refer to it in my charts as “Level 0”. I deem Level-1 readings to be moderately unhealthy and consider Level-2 or higher to be dangerously toxic, from which I endeavor to protect myself and my household by taking the measures described on this site’s Self-protection page.

While no weather-related forecast can ever be perfect, my predictions have proven over time to be roughly 70% accurate.