  We study shallow moist Rayleigh-Benard convection in the Boussinesq
approximation in three-dimensional direct numerical simulations. The
thermodynamics of phase changes is approximated by a piecewise linear equation
of state close to the phase boundary. The impact of phase changes on the
turbulent fluctuations and the transfer of buoyancy through the layer is
discussed as a function of the Rayleigh number and the ability to form liquid
water. The enhanced buoyancy flux due to phase changes is compared with dry
convection reference cases and related to the cloud cover in the convection
layer. This study indicates that the moist Rayleigh-Benard problem offers a
practical framework for the development and evaluation of parametrizations for
atmospheric convection.
