HOPKINS GLOSSARY OF WEATHER TERMS C

ceiling

• The height above the surface of the base of the lowest layer of clouds that obscures more than half the sky; reported for only broken and overcast sky cover. The ceiling may be estimated by visual means or measured by a ceilometer.

ceilometer

• An automatic, recording, cloud-height indicator. A light beam is projected upward on to the cloud base; the reflected light is detected by a photocell and the height is determined by triangulation.

cup anemometer

• A rotation-type anemometer consists of an array of three (or four) hemispherical cups mounted symmetrically about a vertical rotation axis. The rate of rotation of the cup array is a measure of the wind speed, as determined indirectly by gearing a mechanical or electrical counter to the shaft.