dennilfloss
Past Lifer 1957-2014 In Memoriam
The mass of pavement, concrete and some other material retain heat and constitute what are called urban heat islands. Energy use and generation also releases heat into the area (just stay beside a bus exhaust to feel this). Tall buildings concentrate the heat/light and reduce wind exchange (urban canyon effect).
This is why when I see the temperature posted by Environment Canada and taken from the airport station on, say, the Weather Network, I always add a degree in my head to mean what I'll experience going outside smack in the downtown area. This doesn't take into account the humidity (dew point) factor (humidex/heat index/feels like).
The reason they take the temperature readings outside the city, like in airports, is because it's more reliable this way, subject to more air circulation and less affected by the urban heat island effect. Plus you can compare more directly against the vast stretches of rural/forest/desert 'no man's land' between our cities.
The urban heat island effect causes a bigger difference at night when the retained heat is released slowly. Compare this to how it can get freezing at night in a desert as there is little cloud cover and the day's heat radiates really fast back up during the night.
Cities also create their own microclimate and wind conditions.
More details: http://en.wikipedia.org/wiki/Urban_heat_island
This is why when I see the temperature posted by Environment Canada and taken from the airport station on, say, the Weather Network, I always add a degree in my head to mean what I'll experience going outside smack in the downtown area. This doesn't take into account the humidity (dew point) factor (humidex/heat index/feels like).
The reason they take the temperature readings outside the city, like in airports, is because it's more reliable this way, subject to more air circulation and less affected by the urban heat island effect. Plus you can compare more directly against the vast stretches of rural/forest/desert 'no man's land' between our cities.
The urban heat island effect causes a bigger difference at night when the retained heat is released slowly. Compare this to how it can get freezing at night in a desert as there is little cloud cover and the day's heat radiates really fast back up during the night.
Cities also create their own microclimate and wind conditions.
More details: http://en.wikipedia.org/wiki/Urban_heat_island
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