The late-dispersion phase of contrails is simulated with a high-resolution cloud model in which the size distributions of ice crystals are explicitly computed. The cloud optical properties derived from this model are then used to compute the cloud reflectivity using the Monte Carlo method for the shortwave radiation, as well as the outgoing longwave radiative fluxes at the top of atmosphere using the absorption approximation method. Simulations for both the dissipating and persistent contrail scenarios in typical ambient conditions over Taiwan showed that the evolution of contrail morphology is critically controlled by the ambient humidity. Also, contrails may effectively after the local radiative budget, more so for the persistent contrails than the dissipating contrails.