A mercury barometer in which the tube is U-shaped and the upper and lower mercury surfaces have the same diameter.

A self-recording psychrometer.

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

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.

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

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

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

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.

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 ...

Same as geostrophic wind level.

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

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

Solar radiation of selected wavelengths.

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

Pertaining to rain, or more broadly, to precipitation.

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

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

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

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