Nacreous Clouds

Nacreous clouds are located in the stratosphere between 9 and 16 miles high. Their "mother of pearl" colors come from sunlight striking tiny ice crystals inside the clouds. Very low temperatures near -85o C are required to form the crystals, which is why nacreous clouds are seen mainly during winter over places like Alaska, Iceland and Scandinavia. This photo was taken in Trondheim, Norway (12/17/08), by Ivar Marthinusen. For more information click on http://www.spaceweather.com/

Graphic Source and Wind Chill

Here is a graphic source that helps us tell what the wind chill is. What is wind chill? Wind chill is the apparent temperature felt on exposed skin, which is a function of the air temperature and wind speed. The wind chill temperature (often popularly called the wind chill factor) is always lower than the air temperature.