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 ...

A thermometer whose sensitive element has been made to resemble a black body by covering it with lamp black. The thermometer is placed in an evacuated transparent chamber which is maintained at a constant temperature. The instrument responds to insolation ...

A thermometer using transducing elements which deform with temperature. Examples are the bimetallic thermometer and the Bourdon tube type of thennometer.

Automated Weather Observing Station. A self-contained weather station designed to make aviation weather observations without operator involvement.

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 ...

Wind with a speed between 4 and 27 knots (4 and 31 mph); Beaufort scale numbers 2 through 6.

Automated Local Evaluation in Real Time. Network of automatic rain gauges that transmit via VHF radio link when precipitation occurs. Some sites are also equipped with other sensors such as temperature, wind, pressure, river stage or tide level. More info ...

pattern barometer-Mercurial barometer with a fixed scale and cistern and which therefore requires only one adjustment before each reading.

The frequency of a carrier wave.

A hygrometer using goldbeater's skin as the sensitive element. Variations of the physical dimensions of the skin caused by its hygroscopic character indicate relative humidity. (Note: Goldbeater's skin is the prepared outside membrane of the large intesti ...

Apparatus using the combined simultaneous action of a bimetallic thermometer and a hair hygrometer to move a needle in front of a divided scale. fts construction permits dew point variations to be indicated approximately.

Same as balloon cover.

A wind blowing in the same direction as the heading of a moving object. thus assisting the object's intended progress. The opposite of a head wind.

The number of cycles per second between the limits of a frequency band.

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.

An instrument which measures evaporation by measuring the loss of water from a burette reservoir through a ceramic disc.

A type of climatic diagram whose coordinates are some form of temperature vs. a form of humidity or precipitation.

The downward flux of atmospheric radiation passing through a given level surface, usually taken as the earth's surface. This result of infrared (long-wave) absorption and reemission by the atmosphere is the principal factor in the greenhouse effect.

The true freezing point of water. The temperature at which a mixture of air-saturated pure water and pure ice may exist in equilibrium at a pressure of one standard atmosphere.

An ion counter of the aspiration condenser type, used for the measurement of the concentration and mobility of small ions in the atmosphere.