Phase Shift Keying. A form of phase modulation of a data signal performed by a modem for transmission over dedicated wire or phone lines.

A type of recording siphon barometer. The mechanically magnified motion of a float resting on the lower mercury surface is used to record atmospheric pressure on a rotating drum.

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.

An instrument for measuring the ultraviolet in solar and sky radiation.

A defective maximum thermometer of the liquid-inglass type in which the mercury flows too freely through the constriction. Such a thermometer will indicate a maximum temperature that is too low.

See hurricane beacon.

A type of anemometer in which the rotation of an element serves to measure the wind. Rotation anemometers are divided into two classes; those in which the axis of rotation is horizontal, such as the windmill anemometer, and those in which the axis of rota ...

A device for measuring the river stage. Also called stream gauge.

A general term for atmospheric water in any of its forms, i.e. clouds, fog, hail, ice crystals, rain.

By international agreement, a period during which greatly increased observation of world-wide geophysical phenomena is undertaken through the co-operative effort of participating nations. July 1957-December 1958 was the first such year. However, precedent ...

An anemometer which derives wind speed from measurements of dynamic wind pressures. Wind blowing into a tube develops a pressure greater than the static pressure, while wind blowing across a tube develops a pressure less than the static. This pressure dif ...

Sustained winds greater than or equal to 40 mph or gust greater than or equal to 58 mph.

Very small precipitation drops (diameters less than 0.5 mm) that appear to float with air currents while falling in an irregular path. Unlike fog droplets, drizzle falls to the ground.

A mercury-in-glass thermometer which records the temperature upon being inverted and retains its reading until being returned to the first position.

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.

Any and all forms of water particles, liquid or solid, that fall from the atmosphere and reach the ground.

A record obtained from a meteorograph. A chart in which meteorological variables are plotted against time.

A pyrheliometer of the bimetallic type used to measure the intensity of direct solar radiation.

The closeness of agreement among measurements of the same value of the same quantity where the individual measurements are made under different defined conditions, i.e. by different methods or with different measuring instruments.

That stage, on a fixed river gauge, at which overflow of the natural banks of the stream begins to cause damage in any portion of the reach for which the gauge is used as an index.