The Limit of Subarctic Climate (snow, warmest, averages, temperatures)
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We've beaten the subtropical climate to death. Now lets go in the other direction and find the southern limit of the subarctic climate.
According to Koppen classification, the southern limit of Dfc (or northern limit of Dfb) is when there are only 3 or fewer months with average temps above 50F/10C (but at least one month is above that mark). The problem is that places like Peace River and Fort McMurray, Alberta, Prince Albert and Meadow Lake, Saskatchewan, and Flin Flon, Manitoba have 4 months above 50F/10C and are thus temperate. It is hard to image those places being classified in the same group as say Atlanta or Dallas. Even Toronto would be considered tropical compared to those locations. These are real arctic outposts but they still fall short of the subarctic classification.
We've beaten the subtropical climate to death. Now lets go in the other direction and find the southern limit of the subarctic climate.
According to Koppen classification, the southern limit of Dfc (or northern limit of Dfb) is when there are only 3 or fewer months with average temps above 50F/10C (but at least one month is above that mark). The problem is that places like Peace River and Fort McMurray, Alberta, Prince Albert and Meadow Lake, Saskatchewan, and Flin Flon, Manitoba have 4 months above 50F/10C and are thus temperate. It is hard to image those places being classified in the same group as say Atlanta or Dallas. Even Toronto would be considered tropical compared to those locations. These are real arctic outposts but they still fall short of the subarctic classification.
Any thoughts?
I thought annual mean temps and/or winter avgs also help to define subarctic.
As I stated earlier, annual means below 40 F/4 C or 42 F/5 C are low enough to be sub-arctic imho.
Given a colder than normal year there's potential for patchy "permafrost."
Fort McMurray's annual mean is something like 34-35 F.
That would make virtually all of Northern Ontario (North Bay & northward) subarctic.
Seems fair to me, as local residents around North Bay talked as if -40 F/C was a common winter temperature.
The Koppen climate designation only seems to be usefull in places like Alaska
to differentiate between the mildest coastal climates (with milder winters than Toronto, but very-cool summers) from the interior.
Last edited by ColdCanadian; 09-21-2010 at 07:54 PM..
^^ I agree. I think places with annual average temperatures below 5C/42F should be considered subarctic as well as places that regularly get below -30C/-22F every winter without the windchill. To me the subarctic is synonymous with the Taiga or Boreal Forest and in an area where this type of forest predominates the landscape (with much fewer broadleaf trees) is essentially subarctic.
In my opinion, places like Winnipeg, Manitoba - Regina, Saskatchewan - Edmonton, Alberta - Novosibirsk, Russia and Harbin, China should all be classified as Subarctic even though they don't meet Koppen's strict definition of the climate.
We've beaten the subtropical climate to death. Now lets go in the other direction and find the southern limit of the subarctic climate.
According to Koppen classification, the southern limit of Dfc (or northern limit of Dfb) is when there are only 3 or fewer months with average temps above 50F/10C (but at least one month is above that mark). The problem is that places like Peace River and Fort McMurray, Alberta, Prince Albert and Meadow Lake, Saskatchewan, and Flin Flon, Manitoba have 4 months above 50F/10C and are thus temperate. It is hard to image those places being classified in the same group as say Atlanta or Dallas. Even Toronto would be considered tropical compared to those locations. These are real arctic outposts but they still fall short of the subarctic classification.
Any thoughts?
In Koppen’s system… I think the difference of whether a zone was Dfc and Dfb… the coldest month was still below -3 C (26.6 F). So in that case locations like Peace River, Fort McMurray, Alberta, Prince Albert and Meadow Lake, Saskatchewan, and Flin Flon, Manitoba…etc would never be in the same zone as Dallas/Atlanta. Places like Dallas/Atlanta have coldest monthly means far above -3 C. So even if these locations had 4 months of 10 C...they would still be in the D zone because their coldest months are below -3 C.
According to this text (An Introduction to Climate – Trewartha)…
Dfb = Cool Summer; Average temp of the warmest month under 22 C (71.6F )…
Dfc = Cool Short Summer; Less than 4 months over 10 C (50 F)…
CC,
Using annual average temperature to define subarctic is a good idea. I would use 5 or 6 C. This would make Montreal or Minneapolis just shy of subarctic.
Deneb,
I could be wrong but my understanding is that those cities you listed are south of the Boreal Forest. They are in the so called "Aspen Parkland" region according to Wikipedia anyway. Other than that I have no problem making them subarctic.
WH,
Yes, Dallas and Atlanta are in Cfa zone according to Koppen ... but the consensus on this forum is that they are too cold (in the winter) for the subtropical category and should be placed in continental/temperate. That category is itself divided into cool summer/hot summer (Dfa and Dfb). But broadly speaking, they would be called temperate, just like Fort McMurray, Prince Albert and others.
CC,
Using annual average temperature to define subarctic is a good idea. I would use 5 or 6 C. This would make Montreal or Minneapolis just shy of subarctic.
Deneb,
I could be wrong but my understanding is that those cities you listed are south of the Boreal Forest. They are in the so called "Aspen Parkland" region according to Wikipedia anyway. Other than that I have no problem making them subarctic.
WH,
Yes, Dallas and Atlanta are in Cfa zone according to Koppen ... but the consensus on this forum is that they are too cold (in the winter) for the subtropical category and should be placed in continental/temperate. That category is itself divided into cool summer/hot summer (Dfa and Dfb). But broadly speaking, they would be called temperate, just like Fort McMurray, Prince Albert and others.
That's true about Winnipeg, Edmonton being in the Aspen Parkland which is you probably know is a mixture of open prairie and patches of Boreal Forest. Regina I think is more open prairie as there aren't many trees there which weren't already planted by people. Harbin and Novosibirsk I'm not sure but I think they're probably in Boreal Forest/Taiga with maybe Harbin having more broadleaf trees would by guess (the southern limit).
I think this is not so much a temperature issue but rather a precipitation issue as to why some subarctic areas (my definition) are parkland, some steppe/prairie and some forest. The lower the rainfall with the combination of lower evapotranspiration, the more open the landscape is likely to be. I guess for me, I typically associate the Taiga with subarctic climates but not all areas with subarctic climate will have the Taiga.
Melbourne has a subarctic climate and is at latitude 38 degrees so it must be one of the northernmost subarctic climates in the southern hemisphere.
Melbourne's annual average temperature is approximately 14C which puts it firmly in the temperate zone. When was the last time Melbourne hit -30C and had 6 months of snow cover?
According to Koppen classification, the southern limit of Dfc (or northern limit of Dfb) is when there are only 3 or fewer months with average temps above 50F/10C (but at least one month is above that mark). The problem is that places like Peace River and Fort McMurray, Alberta, Prince Albert and Meadow Lake, Saskatchewan, and Flin Flon, Manitoba have 4 months above 50F/10C and are thus temperate. It is hard to image those places being classified in the same group as say Atlanta or Dallas. Even Toronto would be considered tropical compared to those locations. These are real arctic outposts but they still fall short of the subarctic classification.
On the other hand, the climate of Campbell Island (south of New Zealand at 53 S) is not even classified as sub-polar (can we use this term so as to be hemisphere-neutral please?) but is actually considered polar, since every month averages below 10 C / 50 F. However, it has an annual mean temp of about 7 C (about the same as Toronto), which is about 6 - 7 C warmer than the places you mentioned. Its coldest month averages well above freezing.
It seems unfair to lump in Campbell Island with the likes of Vostok Station. There is a "maritime subarctic climate" (Cfc) under Koppen, but Campbell Island doesn't even fit into this. The temperature doesn't drop below -4 C in the average year there, so it's relatively mild. "Oceanic tundra" would seem to be the most accurate description, but this kind of climate seems to be virtually limited to Campbell Island, so maybe it doesn't merit its own category. The only other places I'm aware of that has every month averaging above freezing but no month above 10 C / 50 F are nearby Macquarie Island and Ushuaia, Argentina.
The flora of Campbell Island is what you'd expect of a tundra climate. There are no trees (or at least none with rigid trunks) and not really many plants other than a few endemic "mega herbs" which I believe occur nowhere else in the world outside of the NZ subantarctic.
I came upon an interesting note in the Wikipedia article on polar climates:
Quote:
Climatologist Wladimir Köppen demonstrated a relationship between the Arctic and Antarctic tree lines and the 10 °C summer isotherm; i.e., places where the average temperature in the warmest calendar month of the year is below 10 °C cannot support forests. See Köppen climate classification for more information.
Otto Nordenskiöld theorized that winter conditions also play a role: His formula is W = 9 − 0.1 C, where W is the average temperature in the warmest month and C the average of the coldest month, both in degrees Celsius (this would mean, for example, that if a particular location had an average temperature of −20 °C in its coldest month, the warmest month would need to average 11 °C or higher for trees to be able to survive there). Nordenskiöld's line tends to run to the north of Köppen's near the west coasts of the Northern Hemisphere continents, south of it in the interior sections, and at about the same latitude along the east coasts of both Asia and North America. In the Southern Hemisphere, all of Tierra del Fuego lies outside the polar region in Nordenskiöld's system, but part of the island (including Ushuaia, Argentina) is reckoned as being within the Antarctic under Köppen's.
In 1947, Holdridge improved on these schemes, by defining biotemperature: the mean annual temperature, where all temperatures below 0 °C are treated as 0 °C (because it makes no difference to plant life, being dormant). If the mean biotemperature is between 1.5 °C and 3 °C,[1] Holdridge quantifies the climate as subpolar (or alpine, if the low temperature is caused by altitude).
By Nordenskiöl's reckoning, Campbell Island would not meet the requirement for a polar climate (if we define 'polar' as being above the latitudinal treeline) and would be categorised as sub-polar instead.
Under Holdridge's system I suppose Campbell Island would be classed as boreal or cool temperate rather than polar or sub-polar.
In terms of vegetation I would say:
Ice cap (Koppen EF) - no vegetation
Tundra (Koppen ET) - no trees but maybe a few shrubs and bushes
Sub-polar - slow growing, stunted trees, poor agricultural potential
Cool temperate and continental - extensive forest
Feel free to expand on this. Basically, I see the sub-polar region as the transition zone in the vicinity of the (ant)arctic treeline. This region is characterised by a lack of dense forests (similar to a savannah) -- trees may grow, but only in low density and with very stunted growth (such that their wood is unsuitable for carpentry / construction). In many cases, trees may only grow in sheltered microclimates, giving rise to patchy tree formations.
An analogy can be made with alpine tree lines -- seen from the ground it's a sharp transition, but on closer inspection there's a definite gray area between dense forest and a complete lack of trees. The sub-polar region is that same gray area with regard to (ant)arctic treelines.
In Koppen’s system… I think the difference of whether a zone was Dfc and Dfb… the coldest month was still below -3 C (26.6 F). So in that case locations like Peace River, Fort McMurray, Alberta, Prince Albert and Meadow Lake, Saskatchewan, and Flin Flon, Manitoba…etc would never be in the same zone as Dallas/Atlanta. Places like Dallas/Atlanta have coldest monthly means far above -3 C. So even if these locations had 4 months of 10 C...they would still be in the D zone because their coldest months are below -3 C.
According to this text (An Introduction to Climate – Trewartha)…
Dfb = Cool Summer; Average temp of the warmest month under 22 C (71.6F )…
Dfc = Cool Short Summer; Less than 4 months over 10 C (50 F)…
Yes but if Toronto is also a "D" Koppen climate, I don't think it makes sense grouping us in with Peace River, Fort McMurray, Alberta, Prince Albert and Meadow Lake, Saskatchewan, and Flin Flon, Manitoba…etc either.
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