An instrument which measures the transmissivity of the atmosphere between two points for the determination of visual range.

A photometer which measures the intensity of radiation as a function of the frequency (or wavelength) of the radiation.

A systematic observational error due to the characteristics of the observer. The uncertainty in a reading made by an observer may be acertained by a statistical analysis of his or her readings.

A clockwise change in wind direction. Veering winds with height are indicative of warm air advection (WAA).

The unit of force in the centimeter-gram-second system of physical units, i.e. one gm cm per sec2, equal to 7.233 x 10-5 poundal.

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. T ...

The pressure exerted by the atmosphere as a consequence of gravitational attraction exerted upon the "column" of air lying directly above the point in question.

A type of wind vane having a split or V-shaped tail. The apex orients itself to the direction of the wind.

The rate of decrease of pressure per unit distance at a fixed time.

The difference between amounts of precipitation and runoff for a given storm. It is that portion of the precipitation that remains in the basin as soil moisture, surface storage, ground water, etc.

in United States weather observing practice, the highest "instantaneous" wind speed recorded at a station during a specified period, usually the 24-hour observation day. Therefore, a peak gust need not be a true gust of wind.

Strong winds concentrated within a narrow band in the atmosphere. The jet stream often "steers" surface features such as front and low pressure systems.

A wave resulting from the action of wind on a water surface.

A severe weather condition characterized by low temperatures and strong winds bearing a great amount of snow, either falling or picked up from the ground.

A basic equation in daytime visual range theory, relating the apparent luminance of a distant black object, the apparent luminance of the background sky above the horizon, and the extinction coefficient of the atmosphere, or the air layer near the ground. ...

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

Clouds which cover between 6/10 and 9/10 of the sky. See Sky Terminology.

A type of climatic diagram whose coordinates are some form of temperature vs. a form of humidity or precipitation.

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

The attenuation of light.