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Old 01-25-2012, 06:46 PM
 
Location: Toronto
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I'm curious about the relationship between the record highs and average highs for a place, and what determines it.

Relative to coldest lows, it seems there is a lot less variation for record highs from places, across many latitudes. Canada's record high in Saskatchewan is 45 C (113 F), but many true tropical desert climates aren't much higher such as Dubai's 48C (118F). The record highs for many tropical equatorial climates aren't much higher than many continental or high latitude ones. Florida, Singapore and England have such similar record highs.

Overall, it seems that the record high to latitude connection is a lot less strong than many other temperature-related statistics. It's rather interesting to think about it on a grand scale.

A lot of places at low to middle to high latitudes seem to max out in the 100s F as their hottest record temperature (high 30s C/low 40s C) that seems quite a narrow range for heat maximums, that occur from tropical ones to four-season continental ones; there's a huge swath of territory in the world where this is the case.

And then of course, there are the arid, desert, or seasonally dry climes (tropical wet-and-dry or monsoon ones as well as Mediterranean ones, during the months they lack rain) which can peak above 115 F (45/46 C). On the other side, increasingly high latitude or really maritime climes get lower record highs of course, in 90s F or down to the 80s F (30s C or high 20s C). Then very oceanic cool climates and polar ones drop don't even get there. But those have to be really far from the equator or really far from land or both.

Overall though, record highs don't vary too much on the lands of this globe.

What factors influence/cause record highs to not differ so much and so many climates within large areas to max out at such similar limits?

Last edited by Stumbler.; 01-25-2012 at 06:55 PM..
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Old 01-25-2012, 07:22 PM
 
Location: USA East Coast
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Quote:
Originally Posted by Stumbler. View Post
I'm curious about the relationship between the record highs and average highs for a place, and what determines it.

Relative to coldest lows, it seems there is a lot less variation for record highs from places, across many latitudes. Canada's record high in Saskatchewan is 45 C (113 F), but many true tropical desert climates aren't much higher such as Dubai's 48C (118F). The record highs for many tropical equatorial climates aren't much higher than many continental or high latitude ones. Florida, Singapore and England have such similar record highs.

Overall, it seems that the record high to latitude connection is a lot less strong than many other temperature-related statistics. It's rather interesting to think about it on a grand scale.

A lot of places at low to middle to high latitudes seem to max out in the 100s F as their hottest record temperature (high 30s C/low 40s C) that seems quite a narrow range for heat maximums, that occur from tropical ones to four-season continental ones; there's a huge swath of territory in the world where this is the case.

And then of course, there are the arid, desert, or seasonally dry climes (tropical wet-and-dry or monsoon ones as well as Mediterranean ones, during the months they lack rain) which can peak above 115 F (45/46 C). On the other side, increasingly high latitude or really maritime climes get lower record highs of course, in 90s F or down to the 80s F (30s C or high 20s C). Then very oceanic cool climates and polar ones drop don't even get there. But those have to be really far from the equator or really far from land or both.

Overall though, record highs don't vary too much on the lands of this globe.

What factors influence/cause record highs to not differ so much and so many climates within large areas to max out at such similar limits?
From what I understand, your hunch is right about max highs in tropical areas at least:

Despite the myth, it is not excessively high monthly averages but rather the uniformity and monotony of the constant succession of hot months, with no relief, that characterizes the tropical climates. I thought I remember reading that the highest temp ever recorded in Santarem (Amazon) is 96 F…compared to 105 in Chicago and 99 F in Denver.

Last edited by wavehunter007; 01-25-2012 at 07:35 PM..
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Old 01-25-2012, 07:33 PM
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Location: Western Massachusetts
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Quote:
Originally Posted by Stumbler. View Post
Relative to coldest lows, it seems there is a lot less variation for record highs from places, across many latitudes. Canada's record high in Saskatchewan is 45 C (113 F), but many true tropical desert climates aren't much higher such as Dubai's 48C (118F). The record highs for many tropical equatorial climates aren't much higher than many continental or high latitude ones. Florida, Singapore and England have such similar record highs.

Overall, it seems that the record high to latitude connection is a lot less strong than many other temperature-related statistics. It's rather interesting to think about it on a grand scale.

A lot of places at low to middle to high latitudes seem to max out in the 100s F as their hottest record temperature (high 30s C/low 40s C) that seems quite a narrow range for heat maximums, that occur from tropical ones to four-season continental ones; there's a huge swath of territory in the world where this is the case.
If you look at a graph of mid summer solar radiation (ignoring clouds), the amount of incoming radiation is almost flat with latitude until about 60. In fact, the tropical latitudes are getting slightly less sunlight than the mid and high latitudes. So right in the middle of summer, if dry and cloudless the midlatitudes have a similar potential to get as hot as more tropical latitudes.

As to the difference between humid and dry climates, it takes more energy to heat up water than air. Evaporating water uses up energy, so it's much harder for humid places to reach high temperatures. If you looked at the temperatures for Texas this summer, the hottest days had relatively low dew points.
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Old 01-26-2012, 07:55 AM
 
Location: The western periphery of Terra Australis
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It has to do with a lot of factors. Temperature variability during summer is a big one. Areas prone to air-masses that differ vastly in temperature tend to experience the greatest deviations from average. I think some of the most spectacular examples of extreme heat compared to average temperatures are to found in coastal stations in Southern Australia. Moderated by the cool waters of the Southern Ocean, they are also not far from some arid, hot deserts. California is another example. Melbourne's average February maximum is 26.0C, the record is 46.4C, 20C above average. There are probably coastal stations in Southwestern Victoria with deviations as much as 25C above average. Compare it to say Richmond, VA, at a similar latitude, which is maybe 33 to 41C, a mere 8C above average. When winter comes, however, you'll see a lot variability in a place like Melbourne in terms of highs and lows. Average July max in Melbourne is about 13C, extreme is about 23C.

Yes the hottest temperatures do not occur in equatorial areas. Most temperate stations have reported higher extreme maximums than equatorial climates. East Africa seems to be the exception because of it's aridity.
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Old 01-26-2012, 07:58 AM
 
Location: The western periphery of Terra Australis
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Quote:
Originally Posted by nei View Post
If you look at a graph of mid summer solar radiation (ignoring clouds), the amount of incoming radiation is almost flat with latitude until about 60. In fact, the tropical latitudes are getting slightly less sunlight than the mid and high latitudes. So right in the middle of summer, if dry and cloudless the midlatitudes have a similar potential to get as hot as more tropical latitudes.

As to the difference between humid and dry climates, it takes more energy to heat up water than air. Evaporating water uses up energy, so it's much harder for humid places to reach high temperatures. If you looked at the temperatures for Texas this summer, the hottest days had relatively low dew points.
You're right the 'thermal equator' shifts from the tropics at midsummer, which receive maximum solar radiation. So in mid summer in the Northern Hemisphere the thermal equator is at the Tropic of Cancer, in mid summer in the Southern Hemisphere it's at the Tropical of Capricorn. At the equinoxes it's at the equator, and between that anywhere between. The thermal equator is related to the Inter-tropical Convergence Zone (ITCZ) a band associated with warm season instability, thunderstorms and rain.

If you look at summer statistics for stations on the Tropic of Cancer they are as hot or hotter than the equator. Hong Kong's July statistics are pretty much like many equatorial stations in terms of both temperatures, humidity, rainfall, wind patterns and general weather. The equator, however, isn't so much controlled by seasonal monsoons.
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Old 01-26-2012, 08:31 AM
 
Location: Laurentia
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It has to do with the gradation of climates from Continental to Tropical. A good example of this may be to look at the spectrum from Winnipeg to the Amazon. Winnipeg has very warm (or near-hot summers) with records around 100 F, and averaging in the high 70's F. These sort of places have more variability during the Summer, due to the jet streams which are weaker during the Summer still exerting their influence on them (cold and warm fronts). A place like Chicago has much hotter averages in Summer (85/65 F or thereabouts), but less variability because cold and warm fronts don't pass through there as often and don't have as great of an effect. The heat also lasts longer in Chicago as opposed to Winnipeg. So the record highs are a bit hotter.

Now we go to Memphis, where the Summers continue to get hotter and longer but with still less variability. So the Summer heat is more monotonous and with less variation, and the record highs are about the same. This is due to the increasing tropical influence and the lessening Continental influence (which we saw in Winnipeg). The heat in summer actually maxes out at around the Georgia/Florida border, where it gets a bit hotter in the Summer and it lasts a lot longer than in Memphis. Still the record highs are about the same. This is where we get into effects of seasonality, because solar variation is markedly less here than at higher latitudes.

South of here, we get into Miami, where the Summers are actually a bit cooler for average highs, but average lows continue to rise, as does the humidity. Summers also persist for much longer, and there is virtually no variability here, so the record highs begin to get cooler. There is still seasonality from sun angle but it diminishes quite fast.

Then we get into a place like deep into the Caribbean or the Amazon and this trend is even more marked. There is no variability here at all, and no seasonality due to sun angle, so the heat is about the same as it is in Miami, only lasting longer (in this case perpetually). Low temperatures are a bit higher here still and the humidity a bit higher, and record highs are a bit cooler due to the complete lack of variation.


That's my take, and I hope that this spectrum will help understand the grading between hot-summer continental climates and the tropics, in addition to Trimac20's excellent post. It is a strange phenomenon and contributes to my writing off large portions of the world (at least in this interglacial period; whole new opportunities will open up when the next glacial period starts ).

Deserts operate much like this, only they're hotter because they're dry and constantly under the influence of a heat ridge. The sun angle again contributes to a lack of variation, and anyone who's ever spent a long time under a ridge of high pressure in the summer will know that there is often no variation from day to day (just look at Texas 2011). This naturally contributes to a lack of really hot spikes that may produce big departures from average.
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Old 01-26-2012, 08:32 AM
 
Location: Newcastle NSW Australia
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Record highs can be freakish events in many circumstances.
For instance, Sydney's record of 45.3C has been described as a once in a thousand years event, even though New Year's Day 2006 was 44.2C.
The record is nearly 20C above average.
I tend to look more at variability - such as days over 30C, 35C and 40C per year, which can skew averages but also indicate the likelihood of such temps occurring.
Perth for instance on average has 3 days per year over 40C, and 23 days over 35C and 68 days over 30C. This compares with 0.3 days per year over 40C in Sydney - or once every 3 years, 3 days per year over 35C and 15 days per year over 30C.
This makes Sydney's record much more of an anomaly compared to Perths 46.2C at the old weather station in February 1991.'
What is more, Sydney has only twice in history recorded 2 days in a row above 100F - places like Perth and Adelaide would do that virtually every summer.
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Old 01-26-2012, 08:55 AM
 
Location: Leeds, UK
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The record high for England, 38.5C/101.3F is about 18 degrees above average
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Old 01-26-2012, 08:56 AM
 
Location: Vancouver, Canada
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I agree with those who've mentioned coastal desert and Mediterranean areas as places that often have a big distance between their averages and their records.

I'm thinking of places like these:

Albany, Western Australia - Wikipedia, the free encyclopedia
San Francisco - Wikipedia, the free encyclopedia
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Old 01-26-2012, 09:00 AM
 
Location: Buxton, England
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Quote:
Originally Posted by dunno what to put here View Post
The record high for England, 38.5C/101.3F is about 18 degrees above average
Above what average?

The location which recorded that was Gravesend, Kent, where the average high for August is 23C, making it about 15-16C above average.
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