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.

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.

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.

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.

Of equal or constant pressure, with respect to either space or time.

The humidity transducinu element in a Diamond-Hinman radiosonde. Also called electrolytic strip.

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

Solar radiation of selected wavelengths.

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

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

Pertaining to rain, or more broadly, to precipitation.

An instrument which automatically records the measurement of two or more meteorological elements.

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

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

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.

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