Cool Weather And Cloudy Skies Do Not Block All Solar Radiation
Don’t let the clouds and icy weather fool you. We may still receive a moderate level of ultraviolet (UV) rays from the sun.
“Clouds are not good absorbers; most of the UVR is reflected benefit up to the atmosphere. But cloud formations, such as puffy, light cumulous clouds don’t do a good job of blocking UVR, so you’re likely to receive beefy sun exposure,” says Jim Miller, a senior meteorologist at the National Meteorological Center, National Weather Service (NWS).
Also, the level of ultraviolet (UV) radiation begins to rise in the morning, levels off around noon, then falls gradually throughout the day, yet the temperature may continue to rise until the evening.
“UV radiation is not temperature-dependent,” says Long.
A study in Australia found that more people were sunburned on cooler days because they were tricked into thinking they could safely spend more time outdoors.
“Simply because it might be a cooler day, does not mean there is less likelihood of getting sun burnt,” said Kerry O’Hare, the manager of Cancer Council South Australia. “We know most people get sunburned when temperatures are between 18-27 degrees as they are at this time of year.”
Therefore, you can’t always gauge your solar radiation exposure by how hot it is. You still need to protect your skin from the sun.
Solar radiation–visible, infrared and ultraviolet–is the electromagnetic radiation emitted by the sun. Ultraviolet light, composed of UVA, UVB and UVC, is divided wavelengths that are measured in nanometers (nm) and are shorter than visible light. UVA is found along the 320-400 nm range of the electromagnetic spectrum, UVB, along the 280-320 nm range, and UVC, along the 190-280 nm range.
Ultraviolet radiation (UVR) becomes more intense the closer to the equator you disappear. Likewise, the higher into the mountains you go, the thinner and cleaner the air, the more UVR will strike you. UVR also fluctuates with the seasons, time of day, and atmospheric variables, such as clouds, smog and haze.
UVA and UVB vary, depending upon the angle of the sun to the surface of the earth and the relationship of the earth to the sun. What’s more, UVB is also dependent upon the accomplish of the ozone and atmospheric variables, such as haze, says Long. UVC is filtered by the ozone layer.
Sources: interview with meteorologist, Craig Long
You only get sunburt when it’s hot: this and other sun protection myths busted, the Cancer Council Western Australia
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Filed under radiation side effects by on Jan 20th, 2012. 