An instrument for measuring the difference between incoming and outgoing terrestrial radiation.

A curve showing the variation of temperature with height in the free air. See lapse rate.

A graphical representation of a frequency distribution. The range of the variable is divided into class intervals for which the frequency of occurrence is represented by a rectangular column. The height of the column is proportional to the frequency of ob ...

Either of two colored luminous spots that appear at points 22

A measure of the relative power, or of the relative values of two flux densities, especially of sound intensities and radar power densities. The decibel is derived from the less frequently used unit, the bel, named in honor of Alexander Graham Bell.

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

Situated on the side from which the wind blows.

An automatic, recording cloud height indicator.

Difference between the temperatures of the dry-bulb and the wet-bulb thermometers of a psychrometer.

A direct-vision nephoscope which is constructed in the following manner: a comb consisting of a crosspiece containing equispaced vertical rods is attached to one end of a column eight to ten feet long and is supported on a mounting that is free to rotate ...

The range of operating conditions of a device within which operating influences are negligible. The range is usually narrow. Reference operating conditions are the conditions under which reference performance is stated and the base from which the values o ...

An instrument for measuring the relative speed of a fluid. It consists of a concentric pipe arrangement in which the inner pipe is open at one end and the outer pipe is perforated and closed at both ends. Each pipe is connected to a manometer. The unit is ...

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

See calorie.

The distance or length of flow of the air past a point during a given interval of time.

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.

An inert gas. A colorless, monatomic element which is found to occur in dry air to the extent of only 0.000524 percent by volume. Helium is very light, having a molecular weight of only 4.003 and specific gravity referred to air of 0.138. Because helium i ...

An instrument, located at the surface observing station, which is used to record the data presented by a radiosonde aloft.

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

A general term for instruments designed to measure the speed or force of the wind.