It's summertime and being outside and understanding the possibility of sunburn go hand in hand. This time of year, wildfire smoke can be a depressing sight and have a negative impact on air quality and quality of life in general. Wildfire smoke close to the ground affects the air we breath, but smoke several miles up has several silver linings.
Ultraviolet radiation from the sun is a type of high energy that penetrates Earth's atmosphere. The sun emits three bands of this energy: UVA, UVB and UVC. The stratosphere absorbs all UVC radiation, most UVB but no UVA. This radiation contributes to skin damage, premature aging and skin cancer. The measure of ultraviolet radiation that reaches the ground is a tally of the amount of radiation directly from the sun and the amount that is scattered, refracted and reflected by objects in the sky such as clouds, air, water droplets, ice crystals, dust and wildfire smoke.
Smoke in the sky can act just like cloud cover in reducing the amount of radiation that reaches the surface. Wildfire smoke is comprised of small particles that scatter and absorb ultraviolet rays and reduce UV levels. Don't think you can get away without using sunscreen on smoky days. The usual reduction by smoke is only a few percent, but in higher concentrations of thick smoke, the UV can be reduced by more than 50 percent.
On clear days virtually 100% of UV reaches the ground. Scattered clouds transmit 89%, broken clouds transmit about 73%, and overcast skies transmit 31%. Just like clouds, thicker smoke will reduce more UV. Thicker smoke will also have more of a cooling effect on surface temperatures, just like a cloudy day.
Clear blue sky is still preferential, wildfire smoke is still bad but can have a slight benefit if you're a silver lining kind of person.
