A particular pattern of snow sampler having an internal diameter of 1.485 inches so that each inch of water in the sample weighs one ounce.

The ratio of the output of an instrument to the input value, i.e. a rain gauge with a sensitivity of 1 tip per 0.01"

Thermometer used for measuring the lowest temperature attained during a given interval of time, for example, a day.

Either of two colored luminous spots that appear at points 22

An absolute temperature scale with the ice point of pure water defined as 273.16 K. The size of the degree is the same as on the Celsius scale, and the zero point is absolute zero.

Same as wave pole.

A line drawn through geographical points having the same pluvial index.

A recording siphon barometer.

A method of upper air observation consisting of an evaluation of the wind speed and direction, temperature, pressure, and humidity aloft by means of a balloon-borne radiosonde tracked by radar or a radio theodolite.

An instrument which indicates the presence of precipitation. The ombroscope consists of a heated, water-sensitive surface which indicates by mechanical or electrical techniques the occurrence of precipitation.

An aviation weather forecast for a specific flight.

Precipitation composed of liquid water drops more than 0.5 mm in diameter, failing in relatively straight, but not necessarily vertical, paths. Compare to drizzle.

A liquid-in-glass or liquid-in-metal thermometer using mercury as the liquid.

A systematic observational error due to the characteristics of the observer. The uncertainty in a reading made by an observer may be acertained by a statistical analysis of his or her readings.

Physical equipment used in data processing. Compare to firmware, software.

The maximum rate at which precipitation can pass through the surface into the soil, for a given soil in a given condition.

Winds which, over a small area, differ from those which would be appropriate to the general pressure distribution.

An instrument, located at the surface observing station, which is used to record the data presented by a radiosonde aloft.

A sunshine recorder of the type in which the time scale is supplied by the motion of the sun. It consists essentially of a spherical lens which bums an image of the sun upon a specialty prepared card.

A river gauge in which a weight suspended on a wire is lowered to the water surface from a bridge or other overhead structure to measure the distance from a point of known elevation to the water surface.