A measure of the amount of "spin" (or rotation) in the atmosphere.

An instrument designed to measure the effect of sunlight on evaporation from plant foliage. It consists of a porous clay atmometer whose surface has been blackened so that it absorbs radiant energy.

Precipitation composed of liquid water drops more than 0.5 mm in diameter, failing in relatively straight, but not necessarily vertical, paths. Compare to drizzle.

The difference between the input quantity applied to a measuring instrument and the output quantity indicated by the instrument. The inaccuracy of an instrument is equal to the sum of its instrument error and its uncertainty.

The component of the radiosonde which includes the modulating blocking oscillator and the radiofrequency carrier oscillator.

The smallest change in the environment that causes detectable change in the indication of an instrument. Compare to sensitivity.

Forecasting weather by the use of numerical models, run on high speed computers. Most of the NWP for the National Weather Service is done at the National Centers for Environmental Prediction (NCEP).

The temperature at which an object gives out as much radiation as it receives from its surroundings.

See ceilometer.

A rainbow seen in the spray of the ocean. It is optically the same phenomenon as the ordinary rainbow.

Same as fogbow.

The difference between the air temperature and the dew-point. Also called dew-point deficit, dew-point depression.

An instrument which automatically records the voltage applied to it, as a function of time.

A balloon used to carry a radiosonde aloft, considerably larger than pilot balloons or ceiling balloons.

The temperature registered by a thermometer with its bulb at the level of the tops of the grass blades in short turf.

A hydrometeor consisting of a visible aggregate of minute water droplets suspended in the atmosphere near the earth's surface. Fog differs from cloud only in that the base of fog is at the earth's surface while clouds are above the surface.

Negative Vorticity Advection.

A calorimetric radiation instrument of historic interest used for the measurement of outgoing heat radiation from the earth during an interval of time. The time integration is performed by allowing the radiation to fall on an uninsulated vessel containing ...

A device that combines several separate communications signals into one and outputs them on a single line.

A set of regulations set down by the U.S. Civil Aeronautics Board to govern the operational control of aircraft on instrument flight. The abbreviation of this term is seldom used to denote the rules themselves, but is in popular use to describe the weathe ...