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 ...

Precipitation of white, opaque, spherical or conical ice particles that are crisp and easily crushed and that have diameters of 2 to 5 mm.

A method of winds aloft observation accomplished by tracking a balloon-borne radar target or radiosonde with either radar or a radio theodolite.

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

An ice coating with a consistency intermediate between glaze and rime.

Eluding precise prediction, completely irregular.

A graphical device used for the determination of the speed of the geostrophic wind from the isobar or contour-line spacing on a synoptic chart.

The total infrared radiation emitted from the earth's surface. To be carefully distinguished from atmospheric radiation, effective terrestrial radiation, and insolation.

A photometric unit of illuminance or illumination equal to one lumen per square centimeter.

The combined processes by which water is transferred from the earth's surface to the atmosphere: evaporation of liquid or solid water plus transpiration from plants.

Same as luminous intensity.

A series of Nansen-bottle water samples and associated temperature observations resulting from one release of a messenger.

The difference between temperature measurements taken at two significant levels above the ground. Temperatures at 10 and 40 meters are commonly used.

An instrument for measuring radiant energy. See actinometer, Dines radiometer, photometer, Tulipian radiometer.

An instrument used to determine atmospheric pressure or elevation by observing the boiling point of water or both liquids. The sensitivity of the hypsometer increases with decreasing pressure, making it more useful for high altitude work.

Random Access Memory. The memory of a computer which can be read and written into at any location without passing through preceding locations.

The indicating part of an instrument. For example, the hand of a watch or the meniscus of a mercury column.

Difference between the instantaneous wind velocity at a point and the mean wind velocity taken over a given time interval. Also called fluctuation velocity.

The gravity flow of water within soil.

A system of estimating and reporting wind speed, originally based on the effect of various wind speeds on the amount of canvas that a full-rigged nineteenth century frigate could carry.