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Sea smoke and steam fog
Author(s) -
Saunders P. M.
Publication year - 1964
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49709038405
Subject(s) - steaming , fog , humidity , environmental science , advection , atmospheric sciences , water vapor , seawater , salinity , warm front , air temperature , meteorology , geology , thermodynamics , oceanography , geography , physics
The characteristics of fogs resulting from the advection of cold air over warm water (steam fog and sea smoke) are investigated. They are found to occur with air temperatures between 5 and 40°C lower than the water temperature, in winds from calm to gale; they have liquid water contents in the range 0·01‐0·5 gm −3 , extend in height from 1 to 1,500 m and commonly exhibit either a columnar or banded structure. A study of their occurrence in Atlantic waters reveals a marked concentration in the western regions in the winter months because of the proximity of warm ocean and cold continent. Through the use of equations for turbulent transfer it is shown that the occurrence of steaming is related to the well‐known fact that two masses of unsaturated air at different temperatures when mixed together can yield a supersaturated or foggy mixture. In deriving the connexion the equality of transfer coefficients for heat and water vapour is assumed. The circumstances in which steaming occurs are defined. the difference in the temperatures of the air and water must exceed a threshold which is dependent on the humidity of the air and the temperature and salinity of the water: its value, in the range 5·15°C, is a minimum when the air is moist and the water cold and fresh. the liquid water content and vertical extent of steaming increase as the thermal contrast increases. Close agreement is found between observations of the onset of steaming and the computed threshold values.