Eady Wave with Thermal Forcing.

A kind of thermal forcing (negative forcing, i.e., cooling) is introduced into Eady waves in the two-dimensional semigeostrophic system. As a result of the forcing, the potential vorticity is Newtonian-damped to a positive constant value. In the presence of the forcing, Eady waves with wave numbers in some range are destabilized (i.e., the growth rate is augmented compared with the adiabatic case) in the far future. However, in the early period up to about twice [t] (the temporal scale of the considered phenomena), the stabilizing effect (i.e., diminishing growth rate) is dominant. The destabilizing effect clearly emerges only after three to four times [t].