A instrument designed to study small fluctuations of some quantity. The microbarograph is an example of a recording pressure variometer.

Upwarddirected solar radiation, reflected by the earth's surface and the atmosphere.

A pressure-plate anemometer consisting of a plate which is free to swing about a horizontal axis in its own plane above its center of gravity. The angular deflection of the plate is a function of the wind speed. This instrument is not used for station mea ...

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.

Conditions to which a device is subjected, not including the variable measured by the device. See normal operating conditions, reference operating conditions.

See standard atmosphere.

A unit of energy defined as the heat required to raise the temperature of one pound of water one degree Fahrenheit. It is equal to 252.1 calories or to 1055 joules.

A rotation anemometer in which the axis of rotation is horizontal. The instrument has either flat vanes (as in the air meter) or helicoidal vanes (as in the propeller anemometer). The relation between wind speed and angular rotation is almost linear.

A scale with the ice point at zero degrees and the boiling point of water at 80 degrees, with pressure of one atmosphere.

Same as instrument shelter.

A radiosonde whose carrier wave is modulated by audio-frequency signals whose frequency is controlled by the sensing elements of the instrument.

General name for an instrument which measures the earth's magnetic field intensity.

Any device or instrument for measuring salinity, especially one based on electrical conductivity methods.

A wind blowing in a direction perpendicular to the course of a moving object.

The lowest temperature that can be obtained on a wet-bulb thermometer in any given sample of air. Obtained by evaporation of water (or ice) from the muslin wick. Used in computing dew point and relative humidity.

A method of winds aloft observation accomplished by tracking a balloon-borne radar target or radiosonde with either radar or a radio theodolite.

A rain gauge capable of measuring very small amounts of precipitation. Also called micropluviometer, trace recorder.

An instrument for recording global solar radiation.

An instrument for measuring the pressure of gases and vapors. A mercury barometer is a type of manometer.

Generic term for rapid variations in apparent position, brightness, or color of a distant luminous. object viewed through the atmosphere.