A thermodynamic change of state in a system in which there is no transfer of heat or mass across the boundaries of the system. In an adiabatic process, compression always results in warming, expansion in cooling. Compare to diabatic process.

The measurement and computation of wind speeds and directions at various levels above the surface of the earth. Methods include pilot balloon observations, rabals, rawin or rawinsonde observations, radar tracking, or acoustic sounding.

The lowest temperature that can be obtained on a wet-bulb thermometer in any given sample of air. Obtained by evaporation of water (or ice) from the muslin wick. Used in computing dew point and relative humidity.

The direction from which the wind is blowing, measured in points of the compass or in azimuth degrees.

That portion of the atmosphere which is above the lower troposphere. Generally applied to levels above 850 mb.

A rain gauge capable of measuring very small amounts of precipitation. Also called micropluviometer, trace recorder.

A type of anemometer in which the rotation of an element serves to measure the wind. Rotation anemometers are divided into two classes; those in which the axis of rotation is horizontal, such as the windmill anemometer, and those in which the axis of rota ...

Pertaining to measurements or devices in which the output varies continuously, i.e. voltage or rotation signals. Compare to digital.

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

Same as parhelion.

The temperature at which all three phases of a substance can exist in equilibrium. This temperature occurs at only one pressure. The triple-point of water is 273.16 K and is the basis of the Kelvin scale.

The water portion of the earth as distinguished from the solid part, called the lithosphere, and from the gaseous outer envelope, called the atmosphere.

Wind with a speed between 48 and 55 knots (55 and 63 mph), Beaufort scale number 10.

A transducer which converts electromagnetic radiation in the infrared, visible, and ultraviolet regions into electrical quantities such as voltage, current, or resistance. Also called photo cell.

A rain gauge or array of rain gauges designed to measure the inclination and direction of falling rain.

The direction, with respect to magnetic north, from which the wind is blowing. Distinguish from true wind direction.

An instrument which determines the altitude of an object with respect to a fixed level. There are two general types of altimeters: (a) the pressure altimeter, which gives an approximate measure of altitude from a pressure measurement and an assumed standa ...

Physical equipment used in data processing. Compare to firmware, software.

The record of a barograph.

A sunshine recorder of the type in which the time scale is supplied by a chronograph. It consists of two bulbs, one of which is blackened, which communicate through a glass tube of small diameter. The tube is partially filled with mercury and contains two ...