Heat fluxes in an unstably stratified heated or cooled fluid layer

The results of calculating, the heat flux in a horizontal unstably stratified fluid layer heated (cooled) at a constant rate are given. According, to the results, the convective heat fluxes under this time-dependent background temperature condition are determined only by the value of the Rayleigh number and depend neither on height nor on the rate of heating (cooling) of the fluid layer. At a fixed value of the Rayleigh number, the penetrating ability of convection decreases with an increase in the rate of heating (cooling) of the convective layer.