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

Generic term for rapid variations in apparent position, brightness, or color of a distant luminous. object viewed through the atmosphere.

The statement that the viscosity of air is independent of the density of air.

Pyrheliometer based on the comparison of the heating of two identical metal strips, one exposed to radiation, the other to a joule effect.

A conically shaped, copper rain gauge shield.

A conductor or system of conductors for radiating and/or receiving radio energy. Also called aerial.

The minimum temperature shown by a minimum thermometer exposed in an open situation with its bulb at the level of the tops of the grass blades of short turf.

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

Upwarddirected solar radiation, reflected by the earth's surface and the atmosphere.

A thermometer with a muslin-covered bulb which is moistened. used to measure wet-bulb temperature.

A contact anemometer connected to an electrical circuit which is so arranged that the average wind speed is indicated.

The change in the measured transducer output caused by changes in ambient temperature. Usually expressed a percentage of full scale.

See radar theodolite, radio direction-finder.

A flower-like diagram indicating the relative frequencies of different wind directions for a given station and period of time.

Same as fogbow.

NEXt Generation RADar. A NWS network of about 140 Doppler radars operating nationwide.

An instrument for determining the direction of cloud motion. There are two basic designs of nephoscope, the directvision nephoscope and the mirror nephoscope.

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.

See standard atmosphere.

The upper surface of a column of liquid.