A wind blowing in a direction perpendicular to the course of a moving object.

An instrument which measures the effective terrestrial radiation. See Angstrom pyrgeometer.

An atmospheric phenomenon, other than clouds, which obscures a portion of the sky from the point of observation. Also called obscuration.

A measure of the intensity of gusts given by the ratio of the total range of wind speed between gusts and the intermediate periods of lighter wind to the mean wind speed, averaged over both gusts and lulls.

A vent used with pressure sensors to reduce the effect of wind on the pressure inlet. It is normally mounted remotely and connected to the sensor using airtight tubing.

An evaporation pan in which the evaporation is measured from water in a pan floating in a larger body of water.

The temperature at which the liquid and solid forms of a substance may exist in equilibrium at a given pressure (usually one standard atmosphere). The true freezing point of water is known as the ice point.

A type of hygrometer which measures the water vapor content of the atmosphere by means of the absorption of vapor by a hygroscopic chemical.

Formation of a single water drop by the union of two or more colliding drops.

A measure, proposed by Angstrom, of the precipitation effectiveness of a region.

A clock-driven instrument mounting which automatically and continuously points in the direction of the sun. It is used with a pyrheliometera,hen continuous direct solar radiation measurements are required.

Area of a computer or other device where various logic and control elements are interconnected. Often a printed circuit board into which other circuit boards plug at right angles.

Thermometer used for measuring the highest temperature attained during a given interval of time, for example, a day.

The actual lifting force of an inflated balloon, usually expressed in grams.

A general term for instruments designed to measure the speed or force of the wind.

Abbreviation for visual flight rules, but commonly used to refer to the relatively favorable weather and/or flight conditions to which these rules apply.

A reflecting type telescope with a 45

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

A thermometer using transducing elements which deform with temperature. Examples are the bimetallic thermometer and the Bourdon tube type of thennometer.