An elongated area of relatively high pressure. Usually associated with and most clearly identified as an area of maximum anticyclonic curvature of the wind flow. The opposite of a trough.

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

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 ...

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 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.

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

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

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

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.

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

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

Programmable Read-Only Memory. Read-only memory which can be programmed by the user using a special hardware programmer.

Abbreviation for radio frequency.

Any horizontal wind velocity tangent to the contour line of a constant pressure surface (or to the isobar of a geopotential surface) at the point in question.