Sunshine at different latitudes

**CandyApple** · 01-18-2007, 03:49 AM

I figure this sort of info will help people figure out how far north they can live without getting the winter blues. It's a set of tables showing how what percentage of the possible amount of sunlight will hit the Earth at various latitudes at different times of year. Note that this is the maximum amount, calculated at high noon, without considering atmospheric effects.

I was trying to look up info on how much/how strong the sunshine is at various altitudes a while back. The following are some tables w/info I calculated myself, due to the fact I couldn't find it anywhere. I found info here and there that helped me, and eventually figured out how to do the calculations. After that it was a process of plugging it into the calc program, then putting it into tables in notepad. Then when I cut and paste it here, it didn't line up right, so I reformatted it in Wordpad. I'll probably have to reformat it again once I post.

Now I know why people use Excell!

OK, formating in this thing won't even work, so you're going to have to view the attachment. It's a .txt file.

P.S.- turn off word wrap (it's under format at the top), or it won't look right.

**whitney** · 01-18-2007, 11:13 AM

CandyApple, that was an interesting document.....I've never been as far north as Alaska but have pictures my husband made in Finland in mid-December.
We were in Tasmania in July a few years ago. That was the opposite extreme I guess.

**RodFarlee** · 01-18-2007, 11:49 AM

From Accuweather, a cute little map of percent possible sunshine:

NOAA monthly & annual sunshine data for major US cities:
http://www.ncdc.noaa.gov/oa/climate/...ccd/pctpos.txt

The National Atlas of the United States of America provides the following maps (may take some time to view):

Monthly Sunshine (2.26MB)
http://www.lib.utexas.edu/maps/natio...0/ca000072.jpg

Larger version (6.36MB)
http://www.lib.utexas.edu/maps/natio...0072_large.jpg

Annual Sunshine and Evaporation (937K)
http://www.lib.utexas.edu/maps/natio...0/ca000073.jpg

Larger version (2.60MB)
http://www.lib.utexas.edu/maps/natio...0072_large.jpg

**jabm67** · 01-18-2007, 11:49 AM

You can get specific numbers like these custom-computed for any place you want at the US Naval Observatory's Astronomical Applications Department page. Select the "Data Services" link in the sidebar and scan down to what you want. It recognizes major place names, or you can enter latitude and longitude.

**CandyApple** · 01-20-2007, 12:41 AM

Ooh, good stuff. I was about to go looking for something that calculates day length, but I think the sunrise/sunset chart will do just fine.

Here's a site that gives solar insulation: Monthly Latitude Insolation The output is in watts. I had to "view source" and save as a .txt file it to save it properly on my hard drive. (You can tell I love .txt files, lol). It's the total amount of sunshine that will hit in a given month at a given latitude, and also lists the total for the year. Important for knowing how effective a solar panel would be in different areas, I think, especially combined with the map RodFarlee gave. Ooh, I've been to that utexas site, Rod. Got stuff saved on my hard drive from there!

One thing that I've noticed that's interesting is the further south you are, the faster the sun sets. When I went to Arizona last October I'd pop in the grocery store thinking, "It's nice and light out. Sun'll be up for a good many hours, yet." Then I'd come out less than an hour later and it was sunset! What a shock!

I couldn't go by the it's bright outside, I've got plenty of time to go out rule I use here in Anchorage. I'd actually have to look at the clock and say, oh it's X (I forget what hour) o'clock. If I want to go out today I better do it now before the sun sets.

I think why that is is because the Earth rotates faster the closer to the equator you are, and slower the closer towards the poles you are. Slower rotation = longer sunset. Heck, at the poles (90 degrees latitude) A "day" takes the whole year, from nightime to sunrise to sunset. The day is twenty four hours long, the only thing is it gets brighter the closer it is to the solstice.

That's one thing I'll miss when I leave AK- the looong periods of dusk before the sun is gone for the night.

**MyAzi** · 01-20-2007, 03:14 AM

You know.. I have to be honest here.. when living in the Palm Springs area in CA for so many years... waking to the sunshine made me depressed. On the occasional overcast day.. I thrived!!! I couldn't wait to open everything up and go out.

I love living up here in Wa. I love the rain and the clouds. I don't mind the short days in winter and the really long days in the summer.

My point... is that even that sunshine all the time can be depressing.

**RodFarlee** · 01-20-2007, 03:33 AM

Quote:

Originally Posted by CandyApple

...One thing that I've noticed that's interesting is the further south you are, the faster the sun sets... I think why that is is because the Earth rotates faster the closer to the equator you are, and slower the closer towards the poles you are. Slower rotation = longer sunset. Heck, at the poles (90 degrees latitude) A "day" takes the whole year, from nightime to sunrise to sunset. The day is twenty four hours long, the only thing is it gets brighter the closer it is to the solstice.

That's one thing I'll miss when I leave AK- the looong periods of dusk before the sun is gone for the night.

The USNO site posted by jabm67 calculates twilight times at any latitude.

The Earth rotates at the same angular velocity everywhere. At the equator, the sun's apparent motion is nearly straight down through the horizon at sunset. Away from the equator, the sun's apparent motion at sunset (and sunrise) is at an angle to the horizon, so it takes longer to rise or set, and twilight lasts longer. That angle very roughly = 90 - latitude, and varies seasonally. Here's some pictures that might help, as it sounds like you're really into this!

CandyApple, I remember twilights lasting all night long in Alaska, too.

MyAzi, I also don't mind the short days in winter as much as I mind the sun staying so low in the south. It doesn't get above the trees!

**jabm67** · 01-22-2007, 12:48 PM

You get "civil twilight" when the Sun is below the horizon, but within 6 degrees of the horizon. The Sun is about half a degree across. The Earth rotates at a very nearly constant rate, 360 degrees in 23 hours 56 minutes.

Rod Farlee has it right: the higher the latitude, the shallower the angle made, relative to the horizon, by the Sun as it's carried by the Earth's rotation (staying, for the moment, with the Earth-centered view). Because that angle is so shallow at high latitudes, the Sun is within 6 degrees of the horizon for a much greater time than at low latitudes.

01-18-2007, 11:13 AM	#2 (permalink)
whitney Junior Member Join Date: Jan 06th, 2007 Posts: 57	Re: Sunshine at different latitudes CandyApple, that was an interesting document.....I've never been as far north as Alaska but have pictures my husband made in Finland in mid-December. We were in Tasmania in July a few years ago. That was the opposite extreme I guess.

01-18-2007, 11:49 AM	#3 (permalink)
RodFarlee American Join Date: Jan 15th, 2007 Posts: 345	Re: Sunshine at different latitudes From Accuweather, a cute little map of percent possible sunshine: NOAA monthly & annual sunshine data for major US cities: http://www.ncdc.noaa.gov/oa/climate/...ccd/pctpos.txt The National Atlas of the United States of America provides the following maps (may take some time to view): Monthly Sunshine (2.26MB) http://www.lib.utexas.edu/maps/natio...0/ca000072.jpg Larger version (6.36MB) http://www.lib.utexas.edu/maps/natio...0072_large.jpg Annual Sunshine and Evaporation (937K) http://www.lib.utexas.edu/maps/natio...0/ca000073.jpg Larger version (2.60MB) http://www.lib.utexas.edu/maps/natio...0072_large.jpg

01-18-2007, 11:49 AM	#4 (permalink)
jabm67 Member Join Date: Jan 16th, 2007 Location: Seattle, WA Posts: 173	Re: Sunshine at different latitudes You can get specific numbers like these custom-computed for any place you want at the US Naval Observatory's Astronomical Applications Department page. Select the "Data Services" link in the sidebar and scan down to what you want. It recognizes major place names, or you can enter latitude and longitude.

01-20-2007, 12:41 AM	#5 (permalink)
CandyApple Back Online! Join Date: Dec 23rd, 2006 Location: Austin, TX Posts: 313	Re: Sunshine at different latitudes Ooh, good stuff. I was about to go looking for something that calculates day length, but I think the sunrise/sunset chart will do just fine. Here's a site that gives solar insulation: Monthly Latitude Insolation The output is in watts. I had to "view source" and save as a .txt file it to save it properly on my hard drive. (You can tell I love .txt files, lol). It's the total amount of sunshine that will hit in a given month at a given latitude, and also lists the total for the year. Important for knowing how effective a solar panel would be in different areas, I think, especially combined with the map RodFarlee gave. Ooh, I've been to that utexas site, Rod. Got stuff saved on my hard drive from there! One thing that I've noticed that's interesting is the further south you are, the faster the sun sets. When I went to Arizona last October I'd pop in the grocery store thinking, "It's nice and light out. Sun'll be up for a good many hours, yet." Then I'd come out less than an hour later and it was sunset! What a shock! I couldn't go by the it's bright outside, I've got plenty of time to go out rule I use here in Anchorage. I'd actually have to look at the clock and say, oh it's X (I forget what hour) o'clock. If I want to go out today I better do it now before the sun sets. I think why that is is because the Earth rotates faster the closer to the equator you are, and slower the closer towards the poles you are. Slower rotation = longer sunset. Heck, at the poles (90 degrees latitude) A "day" takes the whole year, from nightime to sunrise to sunset. The day is twenty four hours long, the only thing is it gets brighter the closer it is to the solstice. That's one thing I'll miss when I leave AK- the looong periods of dusk before the sun is gone for the night.

01-20-2007, 03:14 AM	#6 (permalink)
MyAzi Slave to Sir Azi Join Date: Jan 14th, 2007 Location: Western Washington Posts: 1,306	Re: Sunshine at different latitudes You know.. I have to be honest here.. when living in the Palm Springs area in CA for so many years... waking to the sunshine made me depressed. On the occasional overcast day.. I thrived!!! I couldn't wait to open everything up and go out. I love living up here in Wa. I love the rain and the clouds. I don't mind the short days in winter and the really long days in the summer. My point... is that even that sunshine all the time can be depressing. __________________ FEEL THE FEAR AND DO IT ANYWAY

01-22-2007, 12:48 PM	#8 (permalink)
jabm67 Member Join Date: Jan 16th, 2007 Location: Seattle, WA Posts: 173	Re: Sunshine at different latitudes You get "civil twilight" when the Sun is below the horizon, but within 6 degrees of the horizon. The Sun is about half a degree across. The Earth rotates at a very nearly constant rate, 360 degrees in 23 hours 56 minutes. Rod Farlee has it right: the higher the latitude, the shallower the angle made, relative to the horizon, by the Sun as it's carried by the Earth's rotation (staying, for the moment, with the Earth-centered view). Because that angle is so shallow at high latitudes, the Sun is within 6 degrees of the horizon for a much greater time than at low latitudes.