Naked Science Forum
Life Sciences => The Environment => Topic started by: cheryl j on 11/11/2014 15:01:01
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http://www.citylab.com/weather/2014/11/what-will-be-the-coldest-day-in-your-city-this-year/382536/
I thought this was an interesting article, and something I've wondered about after moving to Canada, and finding that the coldest point of winter did not seem to be in the middle of winter, as it was in other places I had lived, but more like 2/3s of the way through. And Canada has a weird fifth season that I like to call "Sprinter" in March and April where the days are long, bright and sunny, and you can ice fish out on the frozen lake in a t shirt. Nights, of course, are still quite cold.
In warmer climates, the coldest day seems to roughly correlate with the least amount of sunlight. The over all deviations in temperature are obviously much less. Why is winter so much slower to get going, and slower to release its grip in the north/ east? Is it the ability of land and water masses to hold on to heat, in the same way that a big stone farm house is slow to heat and slow to cool down? Or are their other meteorological factors? The article also mentions reflection by snow. Anyway, I thought it was an interesting map.
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The graph was measuring temperature by the thermometer. All other things being equal, I would expect that the coldest day would occur around the Winter solstice (or slightly later due to thermal inertia of the sea - or less thermal inertia of the land).
But the thermometer is not the only way to describe "coldest":
- If you include wind-chill, a windy month will feel colder than a still month.
- We often feel colder as the temperature drops after summer, compared to when that same temperature is reached after Winter. Perhaps because we have acclimatised to the colder temperatures - or perhaps because we are now wearing our winter clothes...
The coldest days for me occur in July/August, because the biggest factor deciding the coldest day is whether you live in the Northern or Southern hemisphere.
If you take a world-wide average, the coldest day probably occurs near aphelion (http://en.wikipedia.org/wiki/Aphelion), which occurs around July 4th.
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I have noticed a change in the south east UK in recent years we used to have a cold November a mild December and any thing up to three cold months in the new year but recently the cold weather has not started until December but warming up by Xmas but little real cold weather in the new year.
The UK is a strange place for weather the late December and late June temperatures are often both about 12°C.
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The UK is weird because our weather comes alternately from northern Europe (about 40% of the time) and the southern USA (about 60%) as the Atlantic cyclones drift across the country to be replaced by the Arctic high pressure system.
The problem with windmills is that the cyclones produce strong winds, but comfortable temperatures,so they generate electricity when it is least needed for heating or cooling, but the high pressure systems produce very little wind or cloud, so we get hot summer days and cold winter nights but no electricity!