A photoelectric spectrophotometer which is used in the determination of the ozone content of the atmosphere.

A type of atmometer. It is a pan used in the measurement of the evaporation of water into the atmosphere. The NWS Class A pan is a cylindrical container 48 inches in diameter and 10 inches deep.

Precipitation of white, opaque, spherical or conical ice particles that are crisp and easily crushed and that have diameters of 2 to 5 mm.

A balloon having a detachable tail which is released when the balloon has undergone a predetermined expansion. It thus serves to measure approximately the density of the atmosphere at the point of release.

A type of wind vane having a split or V-shaped tail. The apex orients itself to the direction of the wind.

A colorless and odorless gaseous element. The lightest and apparently the most abundant chemical element in the universe. However, it is found only in trace quantities in the observable portion of our atmosphere, only about 0.00005 percent by volume of dr ...

A unit of luminous flux. The lumen is equal to the luminous flux radiated into a unit solid angle (steradian) from a small source having a luminous intensity of one candle. An ideal source possessing an intensity of one candle in every direction would rad ...

A graduated scale placed in a position so that the stage of a stream may be read directly from it. Staff gauges may be placed on bridge piers or pilings, etc., or placed on specially constructed supports.

A hydrometeor consisting of an aggregate of microscopic and more-or-less hygroscopic water droplets suspended in the atmosphere. It reduces visibility to a lesser extent than fog. The relative humidity of mist is often less than 95 percent.

An evaporation pan in which the evaporation is measured from water in a pan floating in a larger body of water.

See mote.

An area of low barometric pressure, with its attendant system of winds. Also called a depression or cyclone.

Particle on which the freezing of water occurs.

Name sometimes used in place of pyranometer as a generic term.

A liquid-in-glass thermometer which uses an organic substance such as alcohol as the thermometer liquid. This type of thermometer has a low freezing point and a high coefficient of expansion. It is less accurate, however, than a mercury thermometer.

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.

Abbreviation for radio frequency.

The upward force produced by the gas in a balloon. It is equal to the free lift plus the weight of the balloon and the attached equipment.

Thermometer for measuring the temperature in the soil at different depths.

A unit of distance equal to 5280 feet. It is sometimes referred to as a land mile.