Fog

Supplementary features and accessory clouds, like the varieties, aid in the clear identification of clouds. The most common supplementary features are mamma, tuba, and virga. They are defined and associated with the parent clouds in the general section. Fog Fog is a cloud on Earth’s surface. It is visible condensation in the atmosphere. Fog varies in depth from a few feet to many hundreds of feet. Its density is variable resulting in visibility from several miles to near zero. It differs from rain or mist in that its water or ice particles are more minute and suspended and do not fall earthward. The forecasting of fog is frequently a difficult task. In addition to knowledge of the meteorological causes of fog formation, it is necessary to have a thorough knowledge of local geography and topography. A slight 5-6 CIRRUS CIRROSTRATUS 20,000 6,500 CIRROCUMULUS CUMULONIMBUS ALTOSTRATUS ALTOCUMULUS NIMBOSTRATUS STRATOCUMULUS CUMULUS STRATUS AG5f0501 Figure 5-1.—Layer diagram of clouds at various levels.