A device used to switch electrical current at a selectable setpoint temperature.

The distance that an observer can see vertically into a surface-based obscuring phenomenon such as fog, rain, or snow. The distance estimate must be based upon ceiling balloon ascensions or ceiling light projector measurements.

An inert gas. A colorless, monatomic element which is found to occur in dry air to the extent of only 0.000524 percent by volume. Helium is very light, having a molecular weight of only 4.003 and specific gravity referred to air of 0.138. Because helium i ...

The ratios, to the mean wind speed, of the average magnitudes of the component fluctuations of the wind along three mutually perpendicular axes.

A basic equation in night visual range theory, relating the illuminance of a point source of light to distance and the transmissivity of the atmosphere.

A self-recording psychrometer.

Precipitation from a cumuliform cloud. Characterized by the suddenness of beginning and ending, by the rapid change in intensity, and usually by a rapid change in the condition of the sky. The solid or liquid water particles are usually bigger than the co ...

An evaluation, according to set procedures, of those weather elements which are most important for aircraft operations. Always includes cloud height or vertical visibility, sky cover, visibility, obstructions to vision, certain atmospheric phenomena, and ...

Video Display Terminal. An input and display device which includes a keyboard and a screen and allows a human to communicate with a computer.

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.

The portion of the precipitation on the land which ultimately reaches the streams. especially the water from rain or melted snow that flows over the surface.

A system of designating meteorological observing stations by number. established and administered by the World Meteorological Organization. Under this scheme, specified areas of the word are divided into "blocks" each bearing a two-number designator. Stat ...

Same as aneroid barometer. Holostelic means wholly made of solids, while aneroid means devoid of liquid.

Any sudden and heavy rain, almost always of the shower type.

Same as rain-intensity gauge.

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

The length of air flow past a wind vane required for the vane to respond to 50 percent of a step change in wind direction. Expressed in feet or meters and calculated from delay time times wind tunnel speed.

The height ascribed to the lowest layer of clouds or obscuring phenomena when it is reported as broken, overcast, or obscuration and not classified as "thin" or "partial." The ceiling is termed unlimited when these conditions are not satisfied. ...

Overflowing by water of the normal confines of a stream or other body of water, or accumulation of water by drainage over areas which are not normally submerged.

A unit of power equal to one joule per second or 10' ergs per second.