The large scale dynamics of warm atmospheric clouds are strongly coupled to small scale turbulence and droplet microphysics. The entrainment-mixing process is crucial in determining cloud evolution and is believed to foster spectral broadening and to enhance droplet collision and coalescence. Temporal scales such as evaporation, phase relaxation and reaction times have been widely used to parameterize the impact of turbulent mixing on cloud evolution. In this thesis their role is investigated through a particle-resolved three-dimensional pseudospectral direct numerical simulation model. The evolution of the cloud-clear air interface at cloud top is modeled as an initial value problem of decaying turbulence.