total sunlight hours at different latitudes

If you were to add the total hours of sunlight in Barrow, Alaska
(northernmost point of the US) over the entire year, would it be the
same as a city on the equator, or any city at any other latitude? And
would it be 4380 hours?

RP

Randall Plant wrote:
If you were to add the total hours of sunlight in Barrow, Alaska
(northernmost point of the US) over the entire year, would it be the
same as a city on the equator, or any city at any other latitude? And
would it be 4380 hours?

RP

At Barrow the sun rises on May 10th, and does not set until
August 1st (83 days). And the sun sets on November 18, and does
not rise until January 23 (66 days).

Here are some calculated figures, for the total direct sunlight
hours in Barrow (for the year 2004, which is a leap year, and using
West 156.77805556 longitude, North 71.28416667 latitude).

Sunlight hours for month 1: 22.392
Sunlight hours for month 2: 197.480
Sunlight hours for month 3: 365.575
Sunlight hours for month 4: 503.991
Sunlight hours for month 5: 716.623
Sunlight hours for month 6: 720.000
Sunlight hours for month 7: 744.000
Sunlight hours for month 8: 578.265
Sunlight hours for month 9: 398.587
Sunlight hours for month 10: 262.655
Sunlight hours for month 11: 64.992
Sunlight hours for month 12: 0.000

total: 4574.560

Changing to West 118.0 longitude and North 34.0 latitude,
which is approximately where Los Angeles is, gives these
numbers:

Sunlight hours for month 1: 315.148
Sunlight hours for month 2: 318.115
Sunlight hours for month 3: 371.983
Sunlight hours for month 4: 391.659
Sunlight hours for month 5: 432.029
Sunlight hours for month 6: 431.033
Sunlight hours for month 7: 438.131
Sunlight hours for month 8: 413.929
Sunlight hours for month 9: 370.251
Sunlight hours for month 10: 349.969
Sunlight hours for month 11: 311.259
Sunlight hours for month 12: 307.365

total: 4453.871

At 150W 0N (southeast of Hawaii, on the equator), the numbers
added up to 4430.441.

Astronomy is far from any expertise I might have, so I'm not
going to try explaining the time differences, or even discuss
it. I'm sure someone in this group can put the correct names
on various phenomena, and precisely describe how it all works.

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

Just my $0.02 worth but it's worth noting that sunrise and sunset are calculated
based upon when the last or first part of the sun's disk disappears or appears
above the horizon. The further north you go, the more time the sun spends right
near the edge of the horizon, so the longer the sun take to set or rise.

Also, differences in the earth's velocity during different parts of the year
probably account for some of the difference, too.

"Floyd L. Davidson" wrote in message
...
Randall Plant wrote:
If you were to add the total hours of sunlight in Barrow, Alaska
(northernmost point of the US) over the entire year, would it be the
same as a city on the equator, or any city at any other latitude? And
would it be 4380 hours?

RP

At Barrow the sun rises on May 10th, and does not set until
August 1st (83 days). And the sun sets on November 18, and does
not rise until January 23 (66 days).

Here are some calculated figures, for the total direct sunlight
hours in Barrow (for the year 2004, which is a leap year, and using
West 156.77805556 longitude, North 71.28416667 latitude).

Sunlight hours for month 1: 22.392
Sunlight hours for month 2: 197.480
Sunlight hours for month 3: 365.575
Sunlight hours for month 4: 503.991
Sunlight hours for month 5: 716.623
Sunlight hours for month 6: 720.000
Sunlight hours for month 7: 744.000
Sunlight hours for month 8: 578.265
Sunlight hours for month 9: 398.587
Sunlight hours for month 10: 262.655
Sunlight hours for month 11: 64.992
Sunlight hours for month 12: 0.000

total: 4574.560

Changing to West 118.0 longitude and North 34.0 latitude,
which is approximately where Los Angeles is, gives these
numbers:

Sunlight hours for month 1: 315.148
Sunlight hours for month 2: 318.115
Sunlight hours for month 3: 371.983
Sunlight hours for month 4: 391.659
Sunlight hours for month 5: 432.029
Sunlight hours for month 6: 431.033
Sunlight hours for month 7: 438.131
Sunlight hours for month 8: 413.929
Sunlight hours for month 9: 370.251
Sunlight hours for month 10: 349.969
Sunlight hours for month 11: 311.259
Sunlight hours for month 12: 307.365

total: 4453.871

At 150W 0N (southeast of Hawaii, on the equator), the numbers
added up to 4430.441.

Astronomy is far from any expertise I might have, so I'm not
going to try explaining the time differences, or even discuss
it. I'm sure someone in this group can put the correct names
on various phenomena, and precisely describe how it all works.

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

That's a very original question, and not one I can answer.
Your question boils down to asking: does every point on the earth in the
course of one year receive the same exposure, measured in hours, to
direct sunlight (ignoring cloud cover)?
Intuitively I would say yes, since the earth rotates and goes right
round the sun, and it ought to even out.
I imagine there are some impressive mathematical equations for this.
Anybody offering?

Randall Plant wrote:
If you were to add the total hours of sunlight in Barrow, Alaska
(northernmost point of the US) over the entire year, would it be the
same as a city on the equator, or any city at any other latitude? And
would it be 4380 hours?

RP

Carusus wrote:
That's a very original question, and not one I can answer.
Your question boils down to asking: does every point on the
earth in the course of one year receive the same exposure,
measured in hours, to direct sunlight (ignoring cloud cover)?
Intuitively I would say yes, since the earth rotates and goes
right round the sun, and it ought to even out.
I imagine there are some impressive mathematical equations for this.
Anybody offering?

I've already posted the results of running a few "impressive
mathematical equations". Clearly it 1) does not work out to 12
hours a day average, and 2) is not the same for all latitudes.

I did expect someone familiar with the proper terms to explain
it, but noboby has. One person did point out that a
significant factor is that the 12 hours per day average would be
when the center of the sun is aligned with the horizon, and
there are more sunlight hours because half of the sun has
already been up, or must go down, at that point.

A factor not mentioned was refraction through the earth's
atomosphere, which causes the sun to be visible even though it
is below the horizon.

The reason higher latitudes get more sunlight hours is the angle
of "apparent movement" of the sun as it goes down. At the
equator the angle is very nearly 90 degrees to the horizon, and
the transition from (for example with a setting sun) a fully
visible sun to a fully obscured sun, is very fast. At high
latitudes that may take literally hours!

Randall Plant wrote:
If you were to add the total hours of sunlight in Barrow,
Alaska (northernmost point of the US) over the entire year,
would it be the same as a city on the equator, or any city at
any other latitude? And would it be 4380 hours? RP

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

"Bill Oertell" wrote in message
...
Just my $0.02 worth but it's worth noting that sunrise and sunset are
calculated
based upon when the last or first part of the sun's disk disappears or
appears
above the horizon. The further north you go, the more time the sun spends
right
near the edge of the horizon, so the longer the sun take to set or rise.

Another practical point:
You don't need the sun to be "up" to have something approaching "daylight".
There is plenty of light with the sun one or two degrees below the horizon,
and enough to be walking about with it at 4 degrees below the horizon.
At 50 to 60 degrees north this effect makes summer evenings very long
indeed.