A warm, dry wind on the lee side of a mountain range, the warmth and dryness due to adiabatic compression upon descent.

A type of cistern barometer in which the level of mercury in the cistern is adjusted to the zero point of the scale before each reading.

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.

A radiosonde which is dropped by parachute from an aircraft for the purpose of obtaining soundings of the atmosphere below.

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

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

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.

Pertaining to rain, or more broadly, to precipitation.

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

Same as parhelion.

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 ...

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

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

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

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.

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

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.

Same as precipitation-evaporation ratio.