aircolumns

Air column, or aircolumns, is a term used in several disciplines to describe a vertical column of air. In meteorology and atmospheric science, it refers to the mass of air above a unit area on the Earth's surface, extending from the ground upward to the top of the atmosphere. This column is typically described by surface pressure and the vertically integrated density. The total mass of the atmosphere is about 5.15 × 10^18 kilograms, yielding an average column mass around 10,000 kilograms per square meter. The effective height of such a column depends on temperature and composition; most of the mass resides in the lower atmosphere, with a characteristic scale height of roughly 8 km under standard conditions.

In acoustics, air columns are the air inside pipes and ducts that support standing waves. The length of the column and whether the ends are open or closed determine the resonant frequencies. For an open tube, the fundamental frequency is approximately v/2L; for a tube closed at one end, it is v/4L, where v is the speed of sound in air. At room temperature, v is about 343 meters per second, so a 0.5-meter column yields about 343 Hz for an open tube and about 171 Hz for a closed tube.

In building and ventilation engineering, vertical air columns influence natural draft and stack effects. The height of the column, along with external temperature differences, drives airflow through shafts and chimneys. The term is thus used in both scientific and practical contexts.

The meaning of air column is context-dependent; in meteorology it denotes a mass of air above a surface, while in acoustics it refers to a resonant air body inside a pipe or duct.