A reversing thermometer which is encased in a strong glass outer shell that protects it against hydrostatic pressure. Compare to unprotected thermometer.

Line drawn through geographical points recording equal amounts of precipitation during a given time period or for a particular storm.

The line-of-sight distance between two objects.

Same as recording rain gauge.

The length of fluid flow (gas or liquid) past a sensor required for the sensor to respond to 63.2% of a step change in speed. Expressed in feet or meters. For anemometers, this value is calculated from time constant times wind tunnel speed.

A current meter consisting of six conical cups, mounted around a vertical axis, which rotate and generate a signal with each rotation. Tail vanes and a heavy weight stabilize the instrument.

A device which converts energy from one form into another, i.e. an ac generator transducer which converts the mechanical motion of anemometer cups into an electrical signal.

A line drawn through geographical points where a given seasonal biological event occurs on the same date.

Wind with a speed between 11 and 16 knots (13 and 18 mph); Beaufort scale number 4.

As used by the U.S. Army Corps of Engineers, the departure (in

A set of rules or conventions used to standardize data transfer between devices.

Snow shower, particularly of a very light and brief nature.

Moisture contained in the soil above the water table, including water vapor which is present in the soil pores. In some cases this term refers strictly to the humidity contained in the root zone of plants.

The processing of the form or mode of a signal so as to make it intelligible to, or compatible with, a given device.

Amount of water, expressed as a depth or as a mass, which would be obtained if all the water vapor in a specified column of the atmosphere were condensed and precipitated.

Precipitation of very small, white opaque particles of ice, fairly flat or elongated, with diameters less than 1 mm. The solid equivalent of drizzle.

An element that can control current without moving parts, heated filaments, or vacuum gaps.

A recording siphon barometer.

Atmospheric layer throughout which there is no change of temperature with height, i.e. a zero lapse rate.

A local variation in the wind direction or speed. This condition can present danger to aircraft, especially at landing, when a sudden shift from headwind to tailwind can cause a rapid loss of airspeed and lift.