Have you ever had a sunburn on a December day? (snowy, city)

[EricS39]

On a bright snowy day in the northern hemisphere at a latitude above 30 degrees north?

Trying to model time in minutes to get a sunburn under low sun angle with snow.

Apparently there is a major magnification of UV-B exposure when the ground is snow/ice but this is even bigger a reflection magnitude at low angle sun.

How I know this?

Usually you don't get sunburnt when sun is not more than 30 degrees above horizon. But for all of Europe and the northern US, this is higher than sun gets in December

Otherwise snow sunburns occur in late winter so curious if anyone had any sunburn effect in December winter or early January.


The simple rule (no ozone factoring and no snow) is that it takes 300 times more time length to incur same exposure as the max at 30 degrees above horizon sun angle). That would mean being outside for 5 hours on a winter snowless day equals 60 seconds outside on the strongest sun exposure level (shadowless noon on equator on equinox for example).

But my guess is on a bright snowy day the true length of time to burn is more like 7 or 8 times max. Not 300

[elnina]

Yes, I had, and it's very much possible. Sunburns can occur any time of year. Even at its low winter angle, sunlight reflects strongly off of white snow, in much the same way it would reflect off water from a pool or lake. ( I think, it's called snow burn)
This is in addition to the direct rays of sunlight already hitting your skin.

[EricS39]

I spent a lot of time thinking about how to model the winter sun phenomenon and I think the best model approach is to artificially assume a higher solar angle than actually is, when you select that there is a snow ground.

Or reslope it so 50=50
45 is the new 40

And then have it so the model treats lower sun angles as if they are higher for calculating time to burn

You have to be careful with the art of modeling exceptions because the curves have to be continuous. Otherwise you can have a model that will say time to burn goes worse when sun drops.

A lot goes into this.

I am using UV wavelengths in increments of 5 and weighting which UV wavelengths are most important in causing damage. The international consensus is the worst UV ray is 305 nanometers

UV wavelengths lower than 305 are way more dangerous but also there's less incident power density (less of them) on the earth's surface and so they aren't as abundant to get you.

The ones above 305 nanometers there's more of but they won't cause as much damage to you as if you are exposed to them

Also the higher the nanometer, the more it is present at lower sun angle

305 nm weights the worst balance

290 to 315 is UVB

320 to 400 is UVA

[Bottletree]

I don't get sunburn unless the UV is above 10, so no I have not. I have never got sunburn in my city, and our max UV is 8.

[Mac15]

Goodness gratious no!!

[ben86]

I remember getting a little bit of colour once out walking by the coast all day on a sunny and windy day in February at 53N with the sun reflecting off the sea, but other than that not even close, and I tend to burn more readily than most people. The feel of the sun here is negligible between early November and early February.

[EricS39]

So for February the sun is around 12 degrees south of equator and your max sun angle at 53N is

90 minus (53+12) = 25

So this supports sun burn potential at or above 25 degrees solar angle above horizon


I think for Europe the notoriety for snow sunburn is the late winter/early spring ski season when the sun angle is at September levels but due to seasonal lag, still winter scene fooling people to believe sun isn't as strong as it is....is responsible for the more serious snowburn

Or obviously the worst of all would be High snow peaks in the Himalayas or Andes or Tasmania where the snow is all due to altitude

As a note of precaution, if you can't sunburn at all that still doesn't say anything about UV-A overexposure.

[ben86]

Originally Posted by EricS39

So for February the sun is around 12 degrees south of equator and your max sun angle at 53N is

90 minus (53+12) = 25

So this supports sun burn potential at or above 25 degrees solar angle above horizon


I think for Europe the notoriety for snow sunburn is the late winter/early spring ski season when the sun angle is at September levels but due to seasonal lag, still winter scene fooling people to believe sun isn't as strong as it is....is responsible for the more serious snowburn

Or obviously the worst of all would be High snow peaks in the Himalayas or Andes or Tasmania

Don't people trekking in the Antarctic need to protect themselves from the sun as well? Think I've read that somewhere, though I don't know what latitude / altitude / time of year we're talking about.

[Joe90]

During the ski season here, it is common to see people with sunburn even during June. Altitude is also a factor, with ski areas here being above 4500 ft.

Around here light sunburn (without snow) is reasonably common for people working outside, from about mid-July. It just takes clear skies under an intense high pressure.

What is more common during winter in areas without snow, is a very light sunburn that turns to a tan; rather than just straight out sunburn.

On the water, potential sunburn is a given at any time of the winter, if the conditions are right.

[EricS39]

Originally Posted by ben86

Don't people trekking in the Antarctic need to protect themselves from the sun as well? Think I've read that somewhere, though I don't know what latitude / altitude / time of year we're talking about.

Antarctica gets a spring/summer trekking season during the light period

On the Antarctica peninsula (60 degrees south of equator) this means a sun angle that gets barely below horizon by night and above 40 during the day. This is not just snow and ice, but with the Antarctic Ozone Hole on top of that , plus the demographic that treks are usually people with light skin tones...that is combination for a very underestimated exposure. In winter you wouldn't have an issue because the sun is only up a few hours a day.

Antarctica is very cold though year-round and has a winter scene in the light period. Actually it's altitude, snow albedo, and ozone hole, and summer level of sun angle, and a fair skinned Scandinavian and Australian ski following