The height at which the maximum wind speed occurs, determined in a winds-aloft observation.

The rate of decrease of pressure per unit distance at a fixed time.

The succession of stages through which water passes on the ground and in the atmosphere: evaporation from land or bodies of water, condensation to form clouds, precipitation, accumulation in the soil or in bodies of water, and re-evaporation.

The inherent imprecision of a given process of measurement, the unpredictable component of repeated independent measurements of the same object under sensibly uniform conditions.

A sudden brief increase in the speed of the wind, followed by a lull or slackening. Compare to peak gust.

A measure of the intrinsic luminous intensity emitted by a source in a given direction. Luminance is a measure only of light. The comparable term for electromagnetic radiation in general is radiance.

Very small precipitation drops (diameters less than 0.5 mm) that appear to float with air currents while falling in an irregular path. Unlike fog droplets, drizzle falls to the ground.

A device used to hold liquid-in-glass maximum and minimum thermometers in the proper recording position inside an instrument shelter, and to permit them to be read and reset. See Townsend support.

A white disk 12" or more in diameter which is lowered into the sea to estimate transparency of the water. The depths are noted at which it first disappears when lowered and reappears when raised.

Snow shower, particularly of a very light and brief nature.

A thermometer whose sensitive element has been made to resemble a black body by covering it with lamp black. The thermometer is placed in an evacuated transparent chamber which is maintained at a constant temperature. The instrument responds to insolation ...

Capacity of a soil or other surface to be penetrated by water sinking into the ground under the force of gravity. It thus expresses the rate of percolation.

Old snow that has become granular and compacted as a result of melting and refreezing.

The inaccuracy that the manufacturer permits when the unit is calibrated in the factory.

Pertaining to the action or effect of the wind. Derived from the name of the Greek god of the winds, Aeolus.

In radiometry, a measure of the intrinsic radiant intensity emitted by a radiator in a given direction.

Negative Vorticity Advection.

Generally, the relative states of inflow, outflow, and storage of moisture over a given area of earth's surface.

In physics, any process in which the flux density (or power, amplitude, intensity, illuminance, etc.) of a "parallel beam" of energy decreases with increasing distance from the source. Attenuation is always due to the action of the transmitting medium its ...

in United States weather observing practice, the highest "instantaneous" wind speed recorded at a station during a specified period, usually the 24-hour observation day. Therefore, a peak gust need not be a true gust of wind.