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This winter, The Citizen’s Tom Spears looks under snow and behind icicles to find out what makes our coldest season tick. It’s a series we call The Science of Winter, and today’s episode, on the first day of winter, looks at one side of cold weather that doesn’t seem to make any sense.
Yes, dear optimists, the days will now grow longer, bringing more solar energy each day, warming us steadily until we reach glorious summer, right?
Dead wrong. The weather will keep on growing colder even as the sun pumps more energy into our lives, and David Phillips can prove it to you two ways.
Phillips is Environment Canada’s senior climatologist, and he knows the value of folklore in understanding weather and climate. Here’s one bit: “As the days lengthen, the cold strengthens,” he says. “And it’s so true.”
For those who want stricter science, Phillips can also show by the numbers that the temperature will drop between two and three degrees (both highs and lows) over the next four weeks. That’s when we reach Jan. 18, 19 and 20, the point he calls “the dead of winter.”
This is because the land and water under us are reservoirs of stored heat, even now.
“The ground is is giving up heat. The lakes and rivers probably too. So that is why we see this delayed effect,” he said. But later in January when ground and water are frozen solid, they will stop releasing warmth into the air.
Ottawa has average highs and lows of -4.1 C and -12.4 C on Dec. 21. By his “dead of winter” we’ll average -6.4 C and -15.7 C. After that, it creeps back up.
But the timing of this dead of winter varies. Phillips went hunting for the coldest average date across the country, and it ranges from Jan. 2 in Victoria to about Feb. 2 in Halifax. One reason why the cold lasts so long along the east coast is the steady delivery of ocean water coming down from the Arctic in the Labrador Current, which is the cold alter-ego of the warm Gulf Stream.
• This year stands out as a warm anomaly in the Great Lakes, Ottawa Valley and St. Lawrence region. The past seven months have all been warmer than average — by about two degrees in most cases, which is a hot streak that Phillips calls “a shocker.”
Before that, last April was a single cold month. But the winter leading up to it was mild too.
“There’s a lot of stored heat out there” in soil and water, Phillips believes, and this has the potential to bring mildness to the start of this winter.
• One change we have just undergone is the annual southward shift of the jet stream. That’s the steady, high-altitude wind current that flows west to east, and it divides cold northern air from warm southern air.
In summer the jet stream is well to the north of Ottawa. That leaves us warm air. But now it has shifted south of the Great Lakes and the U.S. border, leaving us on the cold side.
The change happens in November and makes November a windy, stormy month — except that this year’s November was calmer than most.
November, says Phillips, brings the biggest annual drop in temperature. November on average is about seven degrees colder than October.
• For clock-watchers: Ottawa receives eight hours, 42 minutes and 51 seconds of sunlight on this first day of winter. The winter solstice is traditionally called Midwinter’s Day — midwinter in the sense that it’s the longest night, the dark time when people gathered around a Yule log that burned all night.
We get three seconds more daylight on Thursday. (Woo-hoo!)
By Christmas Day the days have grown 44 seconds longer. After a week of winter we gain two minutes and 10 seconds. And in the coming month (to Jan. 21) there’s a gain of about 57 minutes, while the sun also climbs nearly three degrees higher in the sky, making the sunlight stronger as well as longer.
The high point is of course the first day of summer, June 21, which has 15 hours, 40 minutes and some seconds of daylight and is the longest day of the year.
Though not, Phillips points out, the warmest day of the year. That comes a month later…
tspears@postmedia.com
twitter.com/TomSpears1
查看原文...
Yes, dear optimists, the days will now grow longer, bringing more solar energy each day, warming us steadily until we reach glorious summer, right?
Dead wrong. The weather will keep on growing colder even as the sun pumps more energy into our lives, and David Phillips can prove it to you two ways.
Phillips is Environment Canada’s senior climatologist, and he knows the value of folklore in understanding weather and climate. Here’s one bit: “As the days lengthen, the cold strengthens,” he says. “And it’s so true.”
For those who want stricter science, Phillips can also show by the numbers that the temperature will drop between two and three degrees (both highs and lows) over the next four weeks. That’s when we reach Jan. 18, 19 and 20, the point he calls “the dead of winter.”
This is because the land and water under us are reservoirs of stored heat, even now.
“The ground is is giving up heat. The lakes and rivers probably too. So that is why we see this delayed effect,” he said. But later in January when ground and water are frozen solid, they will stop releasing warmth into the air.
Ottawa has average highs and lows of -4.1 C and -12.4 C on Dec. 21. By his “dead of winter” we’ll average -6.4 C and -15.7 C. After that, it creeps back up.
But the timing of this dead of winter varies. Phillips went hunting for the coldest average date across the country, and it ranges from Jan. 2 in Victoria to about Feb. 2 in Halifax. One reason why the cold lasts so long along the east coast is the steady delivery of ocean water coming down from the Arctic in the Labrador Current, which is the cold alter-ego of the warm Gulf Stream.
• This year stands out as a warm anomaly in the Great Lakes, Ottawa Valley and St. Lawrence region. The past seven months have all been warmer than average — by about two degrees in most cases, which is a hot streak that Phillips calls “a shocker.”
Before that, last April was a single cold month. But the winter leading up to it was mild too.
“There’s a lot of stored heat out there” in soil and water, Phillips believes, and this has the potential to bring mildness to the start of this winter.
• One change we have just undergone is the annual southward shift of the jet stream. That’s the steady, high-altitude wind current that flows west to east, and it divides cold northern air from warm southern air.
In summer the jet stream is well to the north of Ottawa. That leaves us warm air. But now it has shifted south of the Great Lakes and the U.S. border, leaving us on the cold side.
The change happens in November and makes November a windy, stormy month — except that this year’s November was calmer than most.
November, says Phillips, brings the biggest annual drop in temperature. November on average is about seven degrees colder than October.
• For clock-watchers: Ottawa receives eight hours, 42 minutes and 51 seconds of sunlight on this first day of winter. The winter solstice is traditionally called Midwinter’s Day — midwinter in the sense that it’s the longest night, the dark time when people gathered around a Yule log that burned all night.
We get three seconds more daylight on Thursday. (Woo-hoo!)
By Christmas Day the days have grown 44 seconds longer. After a week of winter we gain two minutes and 10 seconds. And in the coming month (to Jan. 21) there’s a gain of about 57 minutes, while the sun also climbs nearly three degrees higher in the sky, making the sunlight stronger as well as longer.
The high point is of course the first day of summer, June 21, which has 15 hours, 40 minutes and some seconds of daylight and is the longest day of the year.
Though not, Phillips points out, the warmest day of the year. That comes a month later…
tspears@postmedia.com
twitter.com/TomSpears1
查看原文...
