An ion counter of the aspiration condenser type, used for the measurement of the concentration and mobility of small ions in the atmosphere.

Same as contact anemometer.

Any emission of light at temperatures below that required for incandescence.

The standard deviation (positive square-root of the variation) of the errors associated with physical measurements of an unknown quantity, or statistical estimates of an unknown parameter or of a random variable.

An instrument which measures the spectral distribution of the intensity of direct solar radiation.

The intensity (flux per unit solid angle) of visible radiation weighted to take into account the variable response of the human eye as a function of the wavelength of light. Usually expressed in candles.

The rate of decrease of temperature with height when unsaturated air is lifted adiabatically (without exchange of heat with its surroundings). The decrease is due to expansion as the air is lifted to a lower pressure.

A mercury barometer of the fixed cistern type in which a moveable scale terminating in an ivory point is used to compensate for the variations in the height of the mercury in the cistern

Dihydrogen oxide, molecular formula H2O.

The process whereby a position on the scale of an instrument is identified with the magnitude of the signal (or input force) actuating the instrument.

A type of electrical thermometer in which the thermal element is a substance whose electrical resistance varies with the temperature. Such thermometers can be made with very short time constants and are capable of highly accurate measurements.

Same as fogbow.

An instrument for measuring the extinction coefficient in water.

Binary Coded Decimal. A coding system in which each decimal digit from 0 to 9 is represented by a 4-digit binary number.

An optical instrument which consists of a sighting telescope mounted so that it is free to rotate around horizontal and vertical axes, with graduated scales so that the angles of rotation may be measured. Used to observe the motion of a pilot balloon.

A rainbow seen in the spray of the ocean. It is optically the same phenomenon as the ordinary rainbow.

A graphical representation of a frequency distribution. The range of the variable is divided into class intervals for which the frequency of occurrence is represented by a rectangular column. The height of the column is proportional to the frequency of ob ...

In general, any object that reflects incident energy. Usually it is a device designed for specific reflection characteristics.

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

Fine dust or salt particles dispersed through a portion of the atmosphere; a type of lithometer. The particles are so small they cannot be felt or seen with the naked eye. Many haze formations are caused by the presence of an abundance of condensation nuc ...