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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.
That was not what i was saying.
No, the maximum solar radiation is not at the tropics at the summer solstice. While the topic of cancer / capricorn has the highest solar angle, the days get longer as you go poleward. Excluding the effect of clouds, on June 21, the amount of solar insolation in the northern hemisphere is almost constant.
It wasn't Gravesend, it was Faversham, which is not as warm as Gravesend.
The august avg high is there 22.5°C so its 16 degrees above average.
You implied it was 20.5°C (by saying 18°C above average) but even places like Lincoln (where I have lived) have an august avg high between 21-22 degrees.
No, the maximum solar radiation is not at the tropics at the summer solstice. While the topic of cancer / capricorn has the highest solar angle, the days get longer as you go poleward. Excluding the effect of clouds, on June 21, the amount of solar insolation in the northern hemisphere is almost constant.
On June 21st (when the sun is directly overhead at 23.5 North)…the area of MAX solar insolation (in cal/cm/cm2) is found between 30 and 40 latitude in the Northern Hemisphere. Your right – at the time of the NH solstice - locations in the Northern Hemisphere tropics are not much different in terms of total solar insolation than places in the high arctic. Of course, the sun can shine longer in the higher latitudes of the Northern Hemisphere than in the lower latitudes – so this bumps up the numbers in the arctic a great deal. However, I don’t think that if you looked at the peak intensity of solar insulation for a shorter time span (6 hrs, 5 hrs, 3 hrs…etc) solar insulation in the northern hemisphere is constant. That map you posted (above) above might be misleading in the sense the time scale is smoothed.
It stands to reason that on June 21 st…places on/near 23.5 North have the most intense solar angle, and therefore receive the most solar energy. As you move northward (in the northern Hemisphere) the solar angle decreases (even though daylight hrs get longer). So the equal numbers you see in the tropics and far northern arctic appear the same, yet in terms of intensity of solar insolation, the tropics and subtropics are still higher. I would think that if you took a single hr, say 12 noon on June 21st at Key West (24 North) and at London (54 north)...soalr insolation is 25% more intense at 24 North.
On June 21st (when the sun is directly overhead at 23.5 North)…the area of MAX solar insolation (in cal/cm/cm2) is found between 30 and 40 latitude in the Northern Hemisphere. Your right – at the time of the NH solstice - locations in the Northern Hemisphere tropics are not much different in terms of total solar insolation than places in the high arctic. Of course, the sun can shine longer in the higher latitudes of the Northern Hemisphere than in the lower latitudes – so this bumps up the numbers in the arctic a great deal. However, I don’t think that if you looked at the peak intensity of solar insulation for a shorter time span (6 hrs, 5 hrs, 3 hrs…etc) solar insulation in the northern hemisphere is constant. That map you posted (above) above might be misleading in the sense the time scale is smoothed.
I think total per day matters more than total per hour for heating. You need heat over the whole day not just a few hours to get a high temperature. Of course the time scale is smoothed to get an average over an entire day, it would be misleading if it wasn't.
The map I showed is at the top of the atmosphere; I think you're giving numbers for the surface, which is different. There's no maximum at the top of the atmosphere (which I chose as to ignore cloud cover) at the 30-40°N. The reason for the difference is that higher latitude tend to have higher cloud cover on average, and the clouds they do get tend to be better at reflecting sunlight. But if the sky is clear, all latitudes in the summer have the potential to reach similar high temperatures if dry. But the highest latitudes can't because they're still warming up from the very cold winter.
Location: The western periphery of Terra Australis
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Quote:
Originally Posted by Derek40
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.
Are you sure? I'm sure I remember Sydney going through heatwaves with a string of 40C+ days. What about during the 1939 event? It's hit 40C for the past 3 days now, and the last day below 100F I can recall seems like almost a week ago. As you say, not unusual at all, although Sydney has the POTENTIAL to get as hot, the 'ideal' conditions are a lot harder to get.
The august avg high is there 22.5°C so its 16 degrees above average.
You implied it was 20.5°C (by saying 18°C above average) but even places like Lincoln (where I have lived) have an august avg high between 21-22 degrees.
Couldn't find averages for the place so used Maidstone which is also in Kent.. didn't think they'd differ too much
Couldn't find averages for the place so used Maidstone which is also in Kent.. didn't think they'd differ too much
Using Maidstone's figures the 38.5 would be 17°C above average. It's still not comparable with how much above average the record is for continental climates at this latitude.
Are you sure? I'm sure I remember Sydney going through heatwaves with a string of 40C+ days. What about during the 1939 event? It's hit 40C for the past 3 days now, and the last day below 100F I can recall seems like almost a week ago. As you say, not unusual at all, although Sydney has the POTENTIAL to get as hot, the 'ideal' conditions are a lot harder to get.
I am sure about the only twice two days in a row over 100F (laughable to places like Perth and Adelaide), and it was last done in November several years ago.
The January 1939 Heatwave event, I recall looking at the stats on SMH on Microfishce at the library and believe the record high may have been broken about 2 or 3 times over the 2 week period, but never 2 days in a row!
Penrith in the outer western suburbs has recorded 46C in January 203 and 45C in February - during the 2004 Febraury heat wave event -not unusual as it has many more days over 30C and 35C than Sydney city, 62 and 18 days respectively - almost Perthesque!
Somehow Sydney city miraculously escaped the heat that time in 2004 while February records tumbled just about every where else in the state, as well as in Brissie and the Goldie.
How about Alaska/northern Canada? Deadhorse in Alaska has an avg. maximum of 7c in June but a record high of 28c in the same month, a difference of 21 degrees
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Are you sure? I'm sure I remember Sydney going through heatwaves with a string of 40C+ days. What about during the 1939 event? It's hit 40C for the past 3 days now, and the last day below 100F I can recall seems like almost a week ago. As you say, not unusual at all, although Sydney has the POTENTIAL to get as hot, the 'ideal' conditions are a lot harder to get.
