A photometric unit of illuminance or illumination equal to one lumen per square meter

An up slope wind due to local surface heating. Opposite of katabatic wind.

See river basin.

The maximum difference in output for any given input (within the specified range) when the value is approached first with increasing, and then with decreasing, input signals. Caused by energy absorption in the elements of the measuring instrument. Usually ...

An anemometer in which the sensor rotation is transmitted to a mechanical counter which directly integrates the air movement past the sensor. Used to determine total air passage (wind run). Average wind speed can be calculated from the difference between ...

Apparatus designed to measure and record the size distribution of raindrops as they occur in the atmosphere.

A protocol similar to RS232 which permits data interchange on multidrop networks of up to 32 nodes using a single twisted pair cable. In order for this protocol to be used, each device on a network must have some level of intelligence in order establish o ...

An instrument used to measure the water vapor content of the air.

Difference between the instantaneous wind velocity at a point and the mean wind velocity taken over a given time interval. Also called fluctuation velocity.

The mass density of a parcel of air expressed in units of mass per volume.

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.

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

Name sometimes given to a transmissometer.

A unit of luminance or brightness equal to 1/d candles per foot'.

Any source of radiant energy, especially electromagnetic energy.

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

A chronograph used to make a time-record of certain measured meteorological elements. The most common type, the triple register, records wind direction and speed, duration of sunshine, and amount of rainfall (sensed respectively by a contact anemometer, M ...

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

General name for a type of instrument which measures the inclination of the wind to the horizontal plane. See bivane.

The decrease of an atmospheric variable with height, the variable being temperature, unless otherwise specified.