For example in Perth, WA today the UV was only “1 – Low” at 6pm, when the sun was still quite high in the sky. The temperature was still 34 degrees and you could really feel the sun’s heat.
How could you be at such low risk of sunburn under those conditions?
In: Planetary Science
UV index isn’t just based on cloud cover and location of the sun in the sky, it’s also very dependent on atmospheric conditions. It’s likely that some invisible conditions existed that was able to block the UV, like above average concentration of ozone. In fact, you can still get sunburn on an overcast day, so even cloud cover doesn’t necessarily decrease UV index.
Temperature however has absolutely nothing to do with UV index.
Growing up I was told it was caused by the hole in the ozone layer above Australia.
Thankfully it’s a dry sun.
I went to IGA earlier to bask in the nights heat at 10pm or so; it was 30 degrees (Celsius).
If you’re at a high latitude, the sun’s rays have to go through more atmosphere. That filters out UV. In the winterish part of the year, even at noon, you’re not going to be getting sunburn or generating Vitamin D.
Hey Perth! It’s the angle of the sun at 6pm. Think of the atmosphere like a thick blanket. At noon, the light of the sun is coming straight down, so it pierces through the atmosphere via the shallowest path. After mid-day, the light comes from an angle, and so the depth of the atmosphere it has to cross is larger; this allows for more scattering due to whatever particulates are in the atmosphere, so less UV intensity. This is also why “dusk” feels like less intense and colored light.
I miss that Perth sunshine.
I bet if you looked back at the UV at noon, it’ll be much higher.
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