Electromagnetic radiation of shorter wavelength than visible radiation but longer than x-rays, between 0.02 and 0.4 micron (200 and 4000 angstrom).

The standard deviation of a sufficiently large number of measurements of the same quantity by the same instrument or method. The non-correctable part of the inaccuracy of an instrument, it represents the limit of measurement precision. The uncertainty of ...

A reversing thermometer (for seawater temperature) which is not protected against hydrostatic pressure. The mercury bulb is therefore squeezed, and the amount of mercury broken off on reversal is a function of both temperature and of hydrostatic pressure.

A relatively small-scale, upward moving current of air.

That portion of the atmosphere which is above the lower troposphere. Generally applied to levels above 850 mb.

A measurement of atmospheric conditions aloft, above the effective range of a surface weather observation. Elements evaluated include temperature, humidity, pressure, wind speed, and wind direction.

Solar and terrestrial radiation directed upward (away From the earth's surface); outgoing radiation.

The rising of cold water from the deeper areas of the ocean to the surface. This phenomena often occurs along the California coast during the spring and summer.

In the direction from which the wind is blowing.

See wind vane.

A recording variometer.

A instrument designed to study small fluctuations of some quantity. The microbarograph is an example of a recording pressure variometer.

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 rain gauge or array of rain gauges designed to measure the inclination and direction of falling rain.

Any quantity, such as force velocity, or acceleration, which has both magnitude and direction at each point in space, as opposed to scalar which has magnitude only. Such a quantity may be represented geometrically by an arrow of length proportional to its ...

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

A tube designed to measure the rate of flow of fluids. It consists of a tube having a constriction or throat at its midsection. The difference between the pressure measured at the inlet and at the throat is a function of the fluid velocity. Compare to Pit ...

A small, moveable graduated scale adjacent and parallel to the main scale of an instrument. It provides a means for interpolating between the graduations of the main scale.

General name for an instrument designed to measure the vertical component of the wind speed. See anemoclinometer.

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.