Root Mean Square. This notation is used frequently with error analysis. In that context, it is the square root of the arithmetic mean of the squares of the deviations of the individual calibration points from the theoretical or ideal response.

A wind blowing in a direction opposite to the heading of a moving object, thus opposing the object's intended progress; the opposite of a tailwind.

A type of modulation in which the frequency of a continuous radio carrier wave is varied in accordance with the properties of a second (modulating) wave.

A balloon designed to float at a constant pressure level. This may be accomplished by a pressure valve which controls the release of ballast so as to maintain flight above a selected pressure level until the supply of ballast is exhausted. See Moby Dick b ...

The pressure unit of the meter-ton-second system of physical units. equal to 10 millibars or 101 dynes per cm2.

A thermometer. the sensitive element of which consists of two metal strips which have different coefficients of expansion and are brazed together. The distortions of the system in response to temperature variations are used as a measure of temperature. It ...

A device used on certain types of instruments to prevent unwanted radiation from affecting the measurement of a quantity. Also called solar radiation shield.

Wind with a speed between 11 and 16 knots (13 and 18 mph); Beaufort scale number 4.

A constant which describes the performance of a wind vane in response to a step change in wind direction. It is calculated from the relative amount of overshoot on two successive swings (half cycles) of a decaying oscillation. This specification is dimens ...

A strong wind characterized by a sudden onset, a duration on the order of minutes, and a rather sudden decrease in speed.

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.

Eluding precise prediction, completely irregular.

An instrument which records the duration of sunshine and gives a quantitative measure of the amount of sunshine by the action of the sun's rays upon blueprint paper. A type of sunshine recorder.

A form of psychrometer with wet-bulb and dry-bulb thermometers mounted on opposite sides of a specialty designed graph of the psychrometric tables. It is so arranged that the intersections of two curves determined by the wet-bulb and dry-bulb readings -yi ...

NEXt Generation RADar. A NWS network of about 140 Doppler radars operating nationwide.

The water volume within a specified portion of a stream channel.

Situated on the side from which the wind blows.

General name for an instrument designed to measure the vertical component of the wind speed. See anemoclinometer.

A temperature scale based on absolute zero. Same as Kelvin temperature scale.

Clouds which cover between 6/10 and 9/10 of the sky. See Sky Terminology.