The record or trace made by a microbarograph.

A hygrometer which includes an arrangement for the time recording of atmospheric humidity.

An evaluation of upper air temperature, pressure, and humidity from radio signals received from a balloon- borne radiosonde.

Precipitation composed of balls or irregular lumps of ice with diameters between 5 and 50 mm.

A line of equal or constant pressure.

Wind with a speed between 48 and 55 knots (55 and 63 mph), Beaufort scale number 10.

A scale with the ice point at zero degrees and the boiling point of water at 80 degrees, with pressure of one atmosphere.

Generally, a measure of the departure of the mean daily temperature from a given standard, one degree day for each degree (

See instrument error, observational error. random error, standard error, systematic error.

An instrument designed to measure quantities of heat. Sometimes used in meteorology to measure solar radiation.

The condition of the atmosphere when the amount of water vapor present is the maximum possible at the existing temperature.

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

The total area drained by a river and its tributaries. Same as watershed.

A fixed support for mounting maximum and minimum thermometers of the liquid-in-glass type. The support holds the thermometers at the correct operating attitude and also permits their rotation for resetting when desired.

The greatest distance at which it is just possible to see and recognize with the unaided eye (1) in the daytime, a prominent dark object against the sky at the horizon, and (2) at night, a known, preferably unfocused, moderately intense light source.

The record obtained from a bolometer.

A rain gauge which is placed under trees or foliage to determine the rainfall in that location. By comparing this catch with that from a rain gauge set in the open. the amount of rainfall which has been intercepted by foliage can be determined.

A device for measuring the frequency of occurrence of atmospherics whose intensity is greater than a predetermined level.

A graphical representation of stage or discharge at a point on a stream as a function of time.

A rotation anemometer in which the axis of rotation is horizontal. The instrument has either flat vanes (as in the air meter) or helicoidal vanes (as in the propeller anemometer). The relation between wind speed and angular rotation is almost linear.