Nacreous Clouds - Nacreous clouds are rare and are rarely found too far south of the poles. They form at an impressive elevation between 68,000 to 100,000 ft where temperatures are at or below -108F. They appear as large thin discs which tend to reflect vivid colors. Due to their high elevations, they can only be seen when the sun is just below the horizon.

Black Body - An object that is a perfect absorber or emitter of radiation. Typically these types of objects are black in color. Black bodies are perfect absorbers of the sun's energy. This is why blacktop will always be hotter than other surfaces on a sunny day.

Noctilucent Clouds - These are a type of cloud that is extremely rare and found very high in the atmosphere. The base of these clouds is typically around 200,000 feet. They are seen as wavy, thin, bluish-white clouds and are best seen at twilight in polar latitudes. The word Noctilucent is derived from the latin word that means "night-shining.'

Cloudburst - A sudden, heavy rain shower that tends to be localized and of a brief duration. Most cloudbursts occur within thunderstorms.

Pluie - This is the french word for rain. To say, "it is raining today" one would say, "Il pleut aujourd'hui."

Rain Gauge - An instrument used to measure the amount of rainfall that occurs over a specific site. A standard rain gauge can measure up to 8 inches. The first known device that was used for measuring rainfall was invented in Korea in 1441.

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.