A type of humidity that considers the mass of water vapor present per unit volume of space. Also considered as the density of the water vapor. It is usually expressed in grams per cubic meter. ABSOLUTE INSTABILITY

A temperature scale with a freezing point of +273° K (Kelvin) and a boiling point of +373° K. ABSOLUTE ZERO

The process in which incident radiant energy is retained by a substance. The absorbed radiation is then transformed into molecular energy. ADIABATIC PROCESS

The horizontal transfer of any property in the atmosphere by the movement of air (wind). Examples include heat and moisture advection. ADVECTION FOG

Statements that are issued by the National Weather Service for probable weather situations of inconvenience that do not carry the danger of warning criteria, but, if not observed, could lead to hazardous situations. Some examples include snow advisories stating possible slick streets, or fog advisories for patchy fog condition causing temporary res [..]

The process of snowflakes massing together in a cluster, maximizing when temperatures are within just a few degrees of freezing. AIR

An extensive body of air throughout which the horizontal temperature and moisture characteristics are similar. AIR MASS THUNDERSTORM

The weight of air above a given point, measured with a barometer. AIR POLLUTION

The maximum level which will be permitted for a given pollutant. Primary standards are to be sufficiently stringent to protect the public health. Secondary standards must protect the public welfare, including property and aesthetics. ALASKAN WINDS

The ratio of the amount of radiation reflected from an object's surface compared to the amount that strikes it. This varies according to the texture, color, and expanse of the object's surface and is reported in percentage. Surfaces with high albedo include sand and snow, while low albedo rates include forests and freshly turned earth. AL [..]