Figure 3.

Urban ground temperatures were often colder than non-urban ground temperatures. (a) Analysis of daily relative urban coldness values (n = 59) reveals that it was often colder in Toronto during winter 2015 than in non-urban areas (curve is a 95% CI loess-smoothed surface). The inset shows the regression for the day circled in red. We hypothesized that relatively cold urban ground temperatures are caused by urban–rural snow depth gradients, and consistent with this expectation we found (b) a significant positive correlation between the daily relative urban coldness index value and regional snow depth on those days. (Online version in colour.)