Weather Glossary. A to C.

{"Weather Terms and Definitions."}

Aams: Artic Airmass.

Ablation:-Depletion of snow and ice due to melting and evaporation.

Accas:-"AltoCumulus-Castellanus" Mid Level Cloud, bases from 8 to 15 Thousand feet, often seen taller than wide, giving them a "turreted" look [A bit like a Castle] Accas is often a sign of instability aloft and may Precede the rapid development of Thunderstorms.[Pronounced:-ack-kis]

Accessory Cloud:- A cloud which is dependant on a larger cloud system for development and continuance. Roll Clouds, Shelf Clouds and Wall Clouds are a good example of this.

AC:- Alto-Cumulus, A cloud of a class characterized by globular massesor rolls in layers or patches.Medium Altitude  8-20,000 feet.

Accretion:- The Growth of a Precipitation frozen particle, with a supercooled liquid water droplet which freezes upon impact.

Adiabatic:- Changes in temperature by the expansion [cooling] or compression [warming] of a body of air as it rises or decends in the atmosphere with no exchange of heat with the surrounding air.

Adiabatic-Lapse-Rate:- The rate of decrease of temperature experienced by a parcel of air when it is lifted in the Atmosphere under the restriction that it cannot exchange heat with its enviroment.

Advection:- Transport of an atmospheric property by the wind.

Advection Fog:-A fog that forms when warm air flows over over a cold surface and cools from below until saturation is reached,IE, Springtime in the Uk when a warm air mass flows over the Cold seas.

Air Mass Thunderstorm:-Generally, a Thunderstorm not associated with a front or other type of synoptic-scale forcing mechanism. Air Mass thunderstorms, typically are associated with warm, humid air in the Summer months. They develop during the afternoon in response to strong insolation and die off quickly after sunset. They generally are less likely to be severe than other types of thunderstorms, but still can produce downbursts, brief heavy rain and hail up to 3/4 inch.

Alaska Current:-A North Pacific Ocean Current flowing counter-clockwise in the Northward flowing [warm]division of the Aleutian Current.

Albedo:- Reflectivity, soil, surface reflectivity. The fraction of radiation striking a surface that is reflected by the Surface.