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

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.

Lowest altitude in the atmosphere over a given location at which the air temperature is 0

The mean difference between the readings of a given instrument and those of a standard instrument.

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.

Solar radiation of selected wavelengths.

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

Same as water year.

The rate of decrease of pressure per unit distance at a fixed time.

The most common of the principal rainbow phenomena, which appears as an arc of about 42

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

Pertaining to rain, or more broadly, to precipitation.

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 ...

A mercury barometer arranged so that the position of the upper or lower meniscus may be measured photographically. In one design the image of the meniscus is formed on a rotating drum covered with sensitized paper so that a continuous record of pressure a ...

A thermometer based upon the principle that the velocity of a sound wave is a function of the temperature of the medium through which it passes. Sonic thermometers possess very short time-constants and eliminate radiation error.

Graduated fixed stake used in regions of abundant snowfall to facilitate the measurement of snow depth.

A unit of luminance or brightness equal to 1/d candles per foot'.

A navigational aid used to facilitate the landing of an aircraft at an airport in instrument weather, i.e. low visibility.

A self-recording psychrometer.