A rotation anemometer in which the axis of rotation is horizontal. The instrument has either flat vanes (as in the air meter) or helicoidal vanes (as in the propeller anemometer). The relation between wind speed and angular rotation is almost linear.

A fabric cone attached to a metal ring and used to indicate wind direction. often at airfields.

A radiosonde whose carrier wave is switched on and off in such a manner that the interval of time between the transmission of signals if a function of the magnitude of the meteorological elements being measured.

A halo consisting of a faint white circle passing through the Sun and running parallel to the horizon for as much as 360

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

A cup anemometer with its shaft mechanically coupled to a magneto.

Precipitation caused by the ascent of moist air over an orographic barrier such as a Mountain range.

The nautical mile is closely related to the geographical mile which is defined as the length of one minute of arc on the earth's equator. By international agreement, the nautical mile is now defined as 1852 meters.

A recording weight barometer.

Occupational Safety and Health Administration. A regulatory office of the U.S. Department of Labor.

Wind with a speed between 4 and 6 knots (4 and 7 mph), Beaufort scale number 2.

A coating of ice, generally clear and smooth. formed by the freezing of supercooled water on a surface.

Same as marine rainbow.

An instrument for determining the direction from which radio waves approach a receiver. It may consist of a manually operated direction indicator, or it may use a servo system to position the antenna automatically in the direction of the incident waves.

That part of snow melt that reaches stream channels as runoff.

The lowest level at which the wind becomes geostrophic in the theory of the Ekman spiral. Also called gradient wind level.

Integrated Flood Observing and Warning System. National Weather Service flood warning program.

A vector term which includes both wind speed and wind direction.

The upper surface of a column of liquid.

Sir Napier Shaw's name for the approximate absolute temperature scale,