In oceanography, it is the horizontal distance between the highest parts of two successive wave crests above the still water level, separated by a trough that is below the still water level, and it is measured in meters. It is the short term variations of the atmosphere, as opposed to the long term, or climatic, changes. It is often referred to in terms of brightness, cloudiness, humidity, precipitation, temperature, visibility, and wind. The mechanical action includes large changes of temperature, high temperatures, frost, or the impact of windborne sand or water. Chemical action includes the chemical reactions between atmospheric constituents in a moist environments or in rain water.
Biological agents are mainly fungi which attack organic material.
The newest generation of Doppler radars, the 1988 Doppler weather radar. The radar units, with help from a set of computers, show very detailed images of precipitation and other phenomena, including air motions within a storm. The name developed based on observations on what kind of weather occurred with certain wind directions. Creative designs often adorn the tops of barns and houses. It is generally associated with cold air east of the Rockies or Appalachians.