A unit of luminance or brightness equal to 1/d candles per foot'.

In a system of moist air, the dimensionless ratio of the mass of water vapor to the total mass of the system.

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

A measure of luminous flux remaining in a light beam after it has passed through a specified distance of the atmosphere.

A term used to describe a sensor (or sensors), the associated transducer(s), and the data readout or recording device.

The ratio of the amount of electromagnetic radiation reflected by a body to the amount incipient upon it, commonly expressed as a percentage. The albedo is to be distinguished from the reflectivity, which refers to one specific wavelength.

Formation of a single water drop by the union of two or more colliding drops.

A class of rain gauge in which the level of the collected rain water is measured by the position of a float resting on the surface of the water.

Temperature to which absolutely dry air would have to be brought in order for it to have the same density as moist air, considered at the same pressure.

A sudden brief increase in the speed of the wind, followed by a lull or slackening. Compare to peak gust.

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 ...

Generally, the relative states of inflow, outflow, and storage of moisture over a given area of earth's surface.

Radiation with wavelengths greater than 4 microns. (In meteorology, same as infrared radiation.)

Pyrheliometer based on the comparison of the heating of two identical metal strips, one exposed to radiation, the other to a joule effect.

The humidity transducinu element in a Diamond-Hinman radiosonde. Also called electrolytic strip.

See sea-water thermometer, reversing thermometer.

A thermometer which utilizes the thermal properties of gas. There are two forms of this instrument: (a) a type in which the gas is kept at constant volume, and pressure is the thermometric property, and (b) a type in which the gas is kept at constant pres ...

An instrument used to measure the water vapor content of the air.

A temperature-sensing element which converts thermal energy directly into electrical energy. In its basic form it consists of two dissimilar metallic conductors connected in a closed loop. Each junction forms a thermocouple. If one thermocouple is maintai ...

A metallic element of atomic weight 200.6 1, unique (for metals) in that it remains liquid under all but very extreme temperatures.