A thermometer consisting of a clock mechanism the speed of which is a function of temperature.

A radiosonde which transmits the indication of the meteorological sensing elements in the form of a code consisting of combinations of dots and dashes.

Situated on the side from which the wind blows.

An absolute pyhrliometer, developed by C.G. Abbott, in which the radiation-sensing element is a blackened water-calorimeter.

A photometer that measures the received intensity of a distance tight source.

A large body of air having similar horizontal temperature and moisture characteristics.

A type of cloud height indicator which uses a searchlight to project vertically a narrow beam of light onto the cloud base. The height of the cloud is determined using a clinometer, located at a known distance from the ceiling light, to measure the angle ...

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

General term for an instrument used to make direct measurements of visual range or measurements of the physical characteristics of the atmosphere which determine the visible range.

Generally, an instrument designed to measure or estimate the blueness of the sky. See Linke-scale.

An instrument which determines the black-body temperature of a substance by measuring its thermal radiation.

See calorie.

The height of the cloud base above the local terrain.

Abbreviation for Instrument Flight Rules, but commonly used to refer to the weather and/or flight conditions to which these rules apply, i.e. low visibility.

Same as radiation pattern. Anticyclone-An area of high atmospheric pressure which has a closed circulation that is anticyclonic (clockwise in northern hemisphere and counterclockwise in southern hemisphere).

Difference between the instantaneous wind velocity at a point and the mean wind velocity taken over a given time interval. Also called fluctuation velocity.

Abbreviation for visual flight rules, but commonly used to refer to the relatively favorable weather and/or flight conditions to which these rules apply.

The decrease of an atmospheric variable with height, the variable being temperature, unless otherwise specified.

A rain gauge or array of rain gauges designed to measure the inclination and direction of falling rain.

A thermoelectric thermometer used for measuring air temperature. The name is derived from the fact that the reference thermocouple is placed in an insulated bottle.