Role of the Water Vapour Greenhouse Effect in the Forecasting Of Fog Occurrence.

Nocturnal measurements of air temperature, relative humidity, temperature inversion-layer thickness, water vapour path and visibility-through-fog, made under non-foggy and foggy conditions in winter over two seasons at Delhi, are analysed to study the decrease in both rate of cooling and temperature inversion-layer thickness during the course of nights followed by fog occurrence. In particular, the decrease in the rate of cooling, compared to that on non-foggy nights, is explained as due to the greenhouse warming effect by a layer of excessive, near-saturated water vapour trapped in a temperature inversion. Next, the linear programming technique is employed to forecast the occurrence of fog, where the visibility-through-fog is minimized through its linear regression equation with the pair of variables, mean air temperature and temperature decrease over one hour (measuring rate of cooling at two convenient hours) in the pre-midnight period. This technique provides feasible solutions that enables one to forecast the occurrence of radiative fog. [ABSTRACT FROM AUTHOR]