Dependence of heat island phenomena on stable stratification and heat quantity in a calm environment

Dependence of heat island atmosphere on stable stratification and the heat quantity is elucidated by (i) visualizing and measuring the thermal flow over a heated source in a calm and stratified conditions in a laboratory experiment, (ii) finding new type of flow patterns, (iii) determining flow states by the PSD gradients, (iv) comparing with the existing results, and (v) discussing physically to extend the laboratory experiment to a real urban atmosphere. The heat quantity transferred from urban areas makes flow patterns tall. The stable stratification suppresses the plume height, increases the swaying amplitude and turbulence, and produces a vortex pair near the plume top. With increasing the heat quantity and/or decreasing the stable stratification, the plume changes from the type of the steady fumigation with local circulations accumulating heat, which agrees well with Okeʹs model, to the types of fumigation with the swaying motion, the mushroom, the maximum amplitude of the swaying motion, having a glasses-like vortex pair, and shedding vortices upwards, wherein the last two types of plumes the urban heat easily dissipates upwards. The results agree well with heat island phenomena which occur during night in winter and gigantic columns of clouds which occur during daytime in summer.