The ceiling classification which is applied when the ceiling height is determined by timing the ascent and disappearance of a ceiling balloon or pilot balloon.

One of several constant-pressure levels in the atmosphere for which a complete evaluation of data derived from upper air observations is required.

Same as rain-intensity gauge.

The volume of liquid water evaporated per unit area in unit time. usually measured as the depth of liquid water lost per unit time from the whole area.

An instrument designed to measure the effect of sunlight on evaporation from plant foliage. It consists of a porous clay atmometer whose surface has been blackened so that it absorbs radiant energy.

A basic equation in night visual range theory, relating the illuminance of a point source of light to distance and the transmissivity of the atmosphere.

A spring which is designed to achieve a fixed spring constant over a wide temperature range. Usually, this involves an alloy with high nickel content such as Ni-Span C. It is common for these springs to be stress relieved at elevated temperature after for ...

The writing component of a recording instrument.

The interval between the lower and upper measuring limits of an instrument, i.e. a thermometer with a range of -35 to 50

The wind speed and direction at various levels in the atmosphere above the level reached by surface weather observations.

The transmission of data collected at a remote location over communications channels to a central station.

A recording hair hygrometer.

(1) The ratio of the speeds of a chemical reaction at two temperatures differing by 10

A wind vane used to obtain the horizontal and vertical components of the wind.

The correctable part of the inaccuracy of an instrument.

Same as fogbow.

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

Situated on the side from which the wind blows.

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

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