The rate of decrease of temperature with elevation, -∂T/∂z, or occasionally ∂T/∂p, where p is pressure. The concept may be applied to other atmospheric variables (e.g., lapse rate of density) if these [..]

A semi-continuous, semi-permanent boundary between polar air masses and tropical air masses. An integral part of an early meteorological theory known as the Polar Front Theory.

A phrase akin to "wintry showers" which has crept into the language because many forecasts have severe word constraints. If well-developed and 'vigorous' thunderstorms are expected [..]

On a thermodynamic diagram, the point of intersection of a sounding curve (representing the vertical distribution of temperature in an atmospheric column) with the saturation mixing ratio line corresp [..]

An infrared camera is a non-contact device that detects infrared energy (heat) and converts it into an electronic signal, which is then processed to produce a thermal image on a video monitor and perf [..]

Instrument with a narrow ( circumsolar) field of view which measures direct normal irradiance. Pyrheliometers are mounted on sun-following trackers so that the instrument is always aimed at the sun.

An instrument used for very accurate measurements of solar irradiance. Absolute cavity radiometers absorb radiation on a blackened conical receiver and are electrically self-calibrating. Absolute cavi [..]

The mass (in grams) of water in a volume (cubic meter) of air; units are g/m3.

(or Total Vorticity) of air particles at any particular point is comprised of two elements: (i) on the rotating earth, air adopts the local vorticity due to the earth's solid-body rotation about [..]

A cloud form that is dependent, for its formation and continuation, upon the existence of one of the major cloud genera. It is often an appendage of the parent cloud (as mamma, incus, tuba, arcus), bu [..]