Turbulent thermal convection in a rotating stratified fluid

Turbulent convection induced by heating the bottom boundary of a horizontally homogeneous, linearly (temperature) stratified, rotating fluid layer is studied using a series of laboratory experiments. It is shown that the growth of the convective mixed layer is dynamically affected by background rotation (or Coriolis forces) when the parameter R = (h(2)Omega(3)/q(0))(2/3) exceeds a critical value of R(c) approximate to 275. Here h is the depth of the convective layer, Omega is the rate of rotation, and q(0) is the buoyancy flux at the bottom boundary. At larger R, the buoyancy gradient in the mixed layer appears to scale as (d (b) over bar /dz)(ml) = COmega(2), where C approximate to 0.02. Conversely, when R < R(c), the buoyancy gradient is independent of 92 and approaches that of the non-rotating case. The entrainment velocity, u(e), for R > R(c) was found to be dependent on Omega according to E = [Ri(1 + COmega(2)/N(2))](-1), where E is the entrainment coefficient based on the convective velocity w* = (q(0)h)(1/3), E = u(e)/w*, Ri is the Richardson number Ri = N(2)h(2)/w(*)(2), and N is the buoyancy frequency of the overlying stratified layer. The results indicate that entrainment in this case is dominated by non-penetrative convection, although the convective plumes can penetrate the interface in the form of lenticular protrusions.