Dynamical modeling of marine boundary layer convection

The interaction between dynamics and infrared radiation is investigated, as well as the problem of entrainment instability in the cloud-topped marine boundary layer. A two-dimensional Boussinesq moist model with a numerical technique (Fourier-Chebysheve tau method) and resolution sufficient to simulate cloud top processes was developed. Previous measurements suggest that the cloud-top radiative cooling is likely to undergo significant horizontal and vertical variability. To investigate the impact of infrared cooling on the boundary layer dynamics, numerical experiments on marine boundary layer convection under various radiative forcings are performed. The results indicate that the model steady state does not depend on the horizontal and the vertical distribution of the cooling when the cooling is confined to the turbulent region. The thermodynamic theory and observations taken during the last fifteen years are summarized. The results indicate that stratocumulus remain solid even when the theoretical entrainment instability criterion is satisfied. Radiatively forced numerical simulations are performed. The cloud cells can decay and reform in a finite time. The appearance and disappearance of cloud holes may have nothing to do with entrainment instability. Signs of stratocumulus breakup were not ovserved even in the situation of strong entrainment.