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

An evaluation of upper air temperature, pressure, and humidity from radio signals received from a balloon- borne radiosonde.

An addition to a rawinsonde system which allows determination of the slant range to the radiosonde.

See hydrologic accounting.

A unit of heat originally defined as the amount of heat required to raise the temperature of water through one degree centigrade (the gram-calorie or small calorie), but this proved to be insufficiently precise. The 15

Technically, the temperature registered by the dry-bulb thermometer of a psychrometer. However, it is identical with the temperature of the air and may also be used in that sense.

An instrument that automatically records pressure and temperature.

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

A general term for instruments designed to measure the speed or force of the wind.

A counterclockwise change in wind direction. Backing winds with height are indicative of cold air advection (CAA).

A box-like structure designed to protect certain meteorological instruments from exposure to direct sunlight, precipitation, and condensation, while at the same time providing adequate ventilation. Instrument shelters are painted white, have louvered side ...

Lowest altitude in the atmosphere over a given location at which the air temperature is 0

A sudden brief increase in the speed of the wind, followed by a lull or slackening. Compare to peak gust.

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

In aviation terminology, route or terminal weather conditions of sufficiently low visibility to require the operation of aircraft under instrument flight rules.

The process by which events in the real world are translated into machine-readable signals.

An instrument used for measuring geometric angles. See radio direction-finder.

An instrument that shows changes in humidity.

Root Mean Square. This notation is used frequently with error analysis. In that context, it is the square root of the arithmetic mean of the squares of the deviations of the individual calibration points from the theoretical or ideal response.

meter-An instrument for measuring the transmissivity of the atmosphere; a type of transmissometer. It consists of a constant- intensity collimated light source located at a suitable distance from a photoelectric cell. Variation in the turbidity of the atm ...