Precipitation from a cumuliform cloud. Characterized by the suddenness of beginning and ending, by the rapid change in intensity, and usually by a rapid change in the condition of the sky. The solid or liquid water particles are usually bigger than the co ...

The time required for an instrument to registe 63.2% of a step change in the variable being measured.

Same as an upper air observation, but commonly used to refer to a single complete radiosonde observation.

The total amount of water transferred to the atmosphere by evapotranspiration.

Downward scattered and reflected solar radiation, coming from the whole hemisphere with the exception of the solid angle of the sun's disc on a surface perpendicular to the axis of this cone.

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

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

A system of physical units based upon the use of the meter, the metric ton (106 grams), and the second as elementary quantities of length, mass, and time, respectively.

One of several constant-pressure levels in the atmosphere for which a complete evaluation of data derived from upper air observations is required.

An atmometer which uses a filter paper disc as the evaporating element. The amount of water evaporated through the paper is read at the graduated tube reservoir.

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.

Same as precipitation- effectiveness index.

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 photometer which measures the intensity of radiation as a function of the frequency (or wavelength) of the radiation.

A type of modulation in which the frequency of a continuous radio carrier wave is varied in accordance with the properties of a second (modulating) wave.

Same as ombrometer.

See photometer.

A type of electrical thermometer in which the thermal element is a substance whose electrical resistance varies with the temperature. Such thermometers can be made with very short time constants and are capable of highly accurate measurements.

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.

A measure of long-term precipitation effectiveness. The ratio of the normal annual rainfall to the normal annual evaporation.