Precipitation composed of white or translucent ice crystals, chiefly in complex branched hexagonal forms.

A self-recording psychrometer.

Diffuse solar radiation which has the same intensity in all directions.

Wind with a speed between 28 and 33 knots (32 and 38 mph); Beaufort scale number 7.

The process of modifying some characteristic of a wave (the carrier) so that it varies in step with the instantaneous value of another wave (the modulating wave) in order to transmit a message. The modified characteristic may be frequency, phase, and/or a ...

The total electromagnetic radiation emitted by the sun. About 99.9 percent of its energy output falls within the wavelength interval from 0. 15 microns to 4.0 microns, with peak intensity near 0.47 microns. About one-half of the total energy in the solar ...

A method of winds aloft observation in which the elevation and azimuth angles of a theodolite are read while visually tracking a pilot balloon. Balloon height data is estimated from assumed balloon ascension rates.

A hygrometer in which the rotation of the hygrometric element is a function of humidity.

Solar radiation of selected wavelengths.

Determination of the total amount of snow covering a watershed or a given region. Both depth and water content of the snow may be measured, and the results may be used to predict the amount of water that will be available after melting.

Any conventional barometer fitted with an extended scale so that atmospheric pressure measurements may be made at both high and low altitudes.

The physical exposure of an instrument. The effect of immediate environment upon the representativeness of the measurements obtained by meteorological instruments is considerable and not always correctable. The purpose of the instrument shelter is to prov ...

In aviation terminology, route or terminal weather conditions of sufficiently low visibility to require the operation of aircraft under instrument flight rules.

Temperature assumed by an unsaturated air parcel when brought adiabatically to a standard pressure (1,000 mb).

Same as geostrophic wind level.

Pertaining to rain, or more broadly, to precipitation.

Apparatus from which the nature and time of precipitation may be determined.

A reversing thermometer which is encased in a strong glass outer shell that protects it against hydrostatic pressure. Compare to unprotected thermometer.

A line drawn through points of equal humidity on given surface.

A precipitation amount of less than 0.005 inches. Also, the record made by any self-registering instrument.