Aurora Borealis - Also known as the northern lights; these luminous radiant emissions from the upper atmosphere can be seen over middle and high latitudes. They are centered around the earth's magnetic poles. These silent fireworks are often seen on clear winter nights in a variety of shapes and colors.

Acid Rain - Rain that has a pH lower than 5. Normally rain has a pH around 5.6. Acid rain occurs due to the presence of sulfuric and nitric acid. Coal burning power plants are the largest contributor to the formation of acid rain, which is toxic to aquatic environments.

Hail-Spike - A radar signature that can occur when severe hail is present in a thunderstorm. The signature is seen as a narrow line of weak reflectivity beyond the thunderstorm. Its occurrence is due to the way the radar pulse is scattered in many directions when it reaches large hailstones. This phenomenon is also referred to as the three-body scatter spike.

Altocumulus Clouds - Are mid-level clouds that are made of water droplets and appear as gray, puffy masses, sometimes rolled out in parallel waves or bands.

Short waves - Relatively small, short-wavelength ripples that occur in the mid to upper levels of the atmosphere. These are basically small-scale troughs that can produce bands of precipitation as they induce upward vertical motions. Short waves tend to move quickly along the prevailing winds and are a common occurrence in the vicinity of a jet stream.

Verglas - Taken from the French language, this is a term that is used to describe a thin coating of ice that forms on an object, such as a rock.

Refraction - The process by which light slows down when passing through a medium, resulting in a bending or change of direction. Refraction explains many atmospheric phenomenon that occur in the sky. For example, sun dogs are seen due to the refraction of sunlight that occurs when there are numerous ice crystals suspended in the sky. Rainbows are also produced by the refraction of sunlight when it passes through raindrops.