This time of year in Hawaii, how long does it take for you to sunburn?

[Ericthebean]

Well I compiled this model. I started with the weighting of how much of each UV wavelength from 290-320 "that's UV-B

320 to 355 is short-wave UV-A

355-400 is long-wave UV-A

UV-B causes burning and UV-A causes aging of the skin

Both are bad but if we are talking burn potential, the focus is on UV-B

UV-B is barely existent when the sun is at a low angle in the sky and then when it gets past a certain height in the Sky it comes in rather quickly. If we ignore all the adjustments and talk about sun angle then here's the solid truth.

The peak of Hawaii sun in January right now...only climbs to 47 degrees above the horizon.
Explained

The sun's most direct Rays right now lie south of Tahiti at 22 degrees south of the equator. Honolulu is 21 degrees North of the Equator. That's a total of 43 latitude degrees removed from the sun's direct Rays.

So if when directly over the most direct Rays the sun is 90 degrees high in the Sky (the max) where 0 would be near sundown... Then right now the highest angle you get in Hawaii is 90 - 43 = 47 degrees high in the sky

That (47 degree high Hawaii January) would be a lower angle than what even Chicago would see at noon by 3rd week in March. Chicago is 42 degrees north so when sun directly on equator at 0 it would only be 42 degrees removed from Chicago. 90 - 42 = 48 high > 47

But Chicago March nobody gets burned with lotion on in less than 45 minutes or even close to that

[whtviper1]

Originally Posted by Ericthebean

The peak of Hawaii sun in January right now...only climbs to 47 degrees above the horizon.
Explained

The sun's most direct Rays right now lie south of Tahiti at 22 degrees south of the equator. Honolulu is 21 degrees North of the Equator. That's a total of 43 latitude degrees removed from the sun's direct Rays.

So if when directly over the most direct Rays the sun is 90 degrees high in the Sky (the max) where 0 would be near sundown... Then right now the highest angle you get in Hawaii is 90 - 43 = 47 degrees high in the sky

That (47 degree high Hawaii January) would be a lower angle than what even Chicago would see at noon by 3rd week in March. Chicago is 42 degrees north so when sun directly on equator at 0 it would only be 42 degrees removed from Chicago. 90 - 42 = 48 high > 47

But Chicago March nobody gets burned with lotion on in less than 45 minutes or even close to that

Nobody is getting sunburned in Chicago because it is to cold outside to lay out in the sun.

Although the angle of the sun in early January in Hawaii is approximately the same as Chicago on the first day of spring that is only one factor in determining UV Index. If one relied strictly on the angle of the sun - then nobody would get sunburned skiing in the winter in Europe or the Mainland.

The ocean and sand (and snow), can easily double a UV index.

Back to your flawed example:

Here is UV in 2013 in Chicago.

http://www.cpc.ncep.noaa.gov/product...les/ord_13.png

In mid-March, the UV in Chicago runs about 4.5

Here is the UV in 2013 in Honolulu.

http://www.cpc.ncep.noaa.gov/product...les/hnl_13.png

In mid-January, UV runs about 7.5 (High) and gets to 8 by the end of the month. A considerable difference to Chicago in mid-March.

[OpenD]

I think think this illustrates the difficulties in trying to model complex behavior versus taking actual observations and measurements. If the model predicts behavior, based on theoretical construction that is not confirmed by actual facts it's generally not going to be considered useful.

[Mikala43]

Originally Posted by ericthebean

i notice the uv chart that is showing 7.5 has shown 6 for past january dates and this wasn't because of cloudy skies. This was the "clear" uv index

this tells me there is something in the air that is magnifying uv index over mainly hawaii. Or ozone could be at a thinner than normal level right now

vog?

[Ericthebean]

Originally Posted by OpenD

I think think this illustrates the difficulties in trying to model complex behavior versus taking actual observations and measurements. If the model predicts behavior, based on theoretical construction that is not confirmed by actual facts it's generally not going to be considered useful.

I adjusted for this UV thing but my adjustments brought my UV index honolulu up to 6, but not quite 7.5...tropical ozone thinner
Ocean reflects back UV
So does hawaiian sand
Heat isn't much a factor though.

I think it is I need to further magnify these factors

I have a good model. I use the solar sun height angle to compare UV relative intensities together for the same place on same calendar day under same weather for same skin type. Then I adjust this level by factors for skin, ozone, weather

The ozone factor varies by season and latitude. It is thinnest in the tropics except at the south pole there is an ozone hole so South Pole gets an exception to the rule. In some years, there's also an arctic ozone hole. Whenever there isn't an ozone hole at the pole, it's thicker ozone column in the higher latitudes and thinner in the tropics. The press over ozone and the poles is simply the concern that their ozone level fluctuates so unpredictably. Where as in the tropics, ozone levels are more stable though they are thinner.

For ski resorts the snowburn modeling system I developed is to rig the solar elevation angle as a little higher than it actually is, but when the true solar elevation angle gets high enough, I phase out the rig factor or otherwise I'm overcompensating for snowburn.

I also have adjustments for altitude. In addition to all this, if you are in a mainland beach city like Long Beach, I will assume if you are not on the beach, your ocean magnitude impact on UV will not be as much as any place on the Hawaiian Islands where the ocean reflections follow you pretty much everywhere on the island. I took all this into account.