Time dependent basic states

A physically important class of problem involves convection in a layer when the basic temperature is not simply a linear function of z, but where it depends also directly on time. For example, any attempt to grow semiconductor crystals in space will be faced with the problem of a gravity field approximately 10-5 times as strong as that on Earth, and hence slight movement of the spacecraft will lead to a basic state that changes with time. Also, any geophysical convection problem driven by solar radiation comes into the category under consideration here since the Sun’s heating effect follows either a diurnal cycle or a yearly one, depending on the timescale involved.