Deep Midwinter

[Cotham Marble]

This is a sort of answer to the "is spring coming" thread, but I thought it might deserve a thread of its own - all theory, no wildlife observations.

Although probably of no academic value I’ve long been irritated by a lack of a workable notion of at what point in the UK winter, the season begins to turn. Of course in a country which stretches from the Orkneys where the dominating factor is the North Atlantic near Arctic climate, to Cornwall where the Gulfstream holds sway, seasonality is inevitably varied geographically, and in addition yearly climatic changes make the effect of seasonality on wildlife a roller coaster from year to year.

The traditional ‘mid winter’, is located in close relation to the observed solar minimum with ‘mid summer’ being located in close relationship to the solar maximum, however because of thermal lag these two mid points actually come closer to marking the effective commencement of the UK winter and summer. In the medieval calendar Candlemass (currently February 2nd) was sometimes described as mid winter being the intermediate quarter day festival between Christmas and Easter, and close to the mid point between the Winter Solstice and Spring Equinox. While Candlemass complies with a calendrical ordering it poorly represents the progress of floral and faunal activity. March 21st is rarely the start of spring in any meaningful sense in most of the UK with lots of activity already underway, and climate change is shifting wildlife activity ever earlier. One could argue on the basis of calendrical neatness that ‘mid winter’ is that point where the ‘darkest’ eighth of the year (December 1st to January 15th) , coincides with the end point of the first quarter of the calendrical winter (Dec 21st – March 21st), the latter date would be the 13th/14th January.

A more sophisticated, though not necessarily scientific approach, is to take the reference point away from the calendar other than for the convenience of measuring time. There are a number of averaged climatic values which have applied to much of the UK over the last century, the far north being an exception. Mean temperature, days of frost and hours of sunshine can be used to define a ‘cold, dark’ period of five months duration running from 1st November to 31st March, the mid point of which is 14th/15th January. So although in traditional terms we still have two months of winter to go, I’m inclined to see the next few days as the point at which the cold and dark period starts to shift toward the brighter warmer seasons.

CM

[AfternoonLemon]

Wow, that certainly is an interesting analysis! I do have wondered the same thing (although not quite as in-depth as that ).

People are always telling you when Winter starts and ends, as if it was fact, but I've never accepted it. The winter solstice is closer to the start of winter than the end, as you say, but really it has little bearing.

I'd also suggest winter varies in it's timing and duration each year, well actually, I won't suggest it, because it's true! So on that basis, I'd say you can only pinpoint the middle of a winter in hindsight.

To calculate the exact middle of the winter at a certain point on the planet, I think the mean temperatures and light levels (UV only?) should be recorded all year round and combined somehow. I'm not sure exactly how they'd need to be combined, whether they be treated as equal in significance or one has more influence on the result than the other.

My 2¢

[artdemole]

Antarctica Has theirs in June.

[Cotham Marble]

Originally Posted by AfternoonLemon

I'd also suggest winter varies in it's timing and duration each year, well actually, I won't suggest it, because it's true! So on that basis, I'd say you can only pinpoint the middle of a winter in hindsight.

Yes that it is of course true. What one can do is to take averaged climatic measures - my suggestion was for mean temperature, days of frost and hours of sunlight - and then use those averaged figures to define a very broad 'trough' the middle of which would equate to the midwinter point. Although individual year's figures would see the mid point move relatative to the calender, the mid point moves far less than the begining and endpoints of the trough appear to have done over the last hundred years. Climate change may have an impact, although it is possible the 'trough' will shrink from both ends, leaving the middle close to where it is now relative to the calender.

Originally Posted by artdemole

Antarctica Has theirs in June.

To be pedantic, the effect of thermal lag combined with the huge differential in day/night length is even greater at the poles, so the mid point of the Antarctic winter is somewhere in July/August.

CM

[Littlesparrow]

The coldest months on average in England are January and February,and it always seemed to snow on my birthday when I was a child.So I expect the Winter weather to do its worst until we get past 11th Feb,not very scientific I know.

[MartinL]

Only one thing sure about the weather.


It'll soon change!

[King Edward]

I'm all in favour of the meteorological definition, with seasons starting on 1st of December, March, June & September. It seems logical that the shortest and longest day should be roughly in the middle of winter/summer, not at the start. I think it's also much more sensible to have seasons divided up with whole months, not to have four months split unequally between two different seasons.

It also ties in with the educational year:
1st September = End of Summer = Back to School

[Meta menardi]

You should have half your fodder left on Valentines day, if you keep livestock.

[AfternoonLemon]

Originally Posted by King Edward

I'm all in favour of the meteorological definition, with seasons starting on 1st of December, March, June & September. It seems logical that the shortest and longest day should be roughly in the middle of winter/summer, not at the start. I think it's also much more sensible to have seasons divided up with whole months, not to have four months split unequally between two different seasons.

It also ties in with the educational year:
1st September = End of Summer = Back to School

That is a good case for an approximation of when winter is, but in reality, it rarely feels like winter until the middle of December at the earliest. With the exception of last year, of course

It's all very well having months divided up neatly, but the truth is that nature decides when winter starts and ends - not us.

[King Edward]

But what do you mean, 'feels like winter'? Who's to say what winter should feel like? If you mean 'very cold', much of the winter isn't actually that wintry. No arbitrary start date can fully take account of the year-to-year vagaries of the weather, but I still think 1st December is a reasonable start date for winter.

If the world (and the UK) continues to get warmer, maybe we should just abolish winter and have three 4 month seasons.