A persistent cirrus anvil (more than 10 hours in time) was observed by the NASA Scanning Raman Lidar on 19 June 2002 during the International H2O Project. The overall cloud height and depth did not change much during this period of time. However, the optical and microphysical properties became two-layered. The top layer featured higher depolarization ratio, larger ice water content and smaller ice crystals, while the lower layer featured the opposite. The depth of the top layer decreased with time while that of the lower layer increased. Furthermore, from radiosonde measurements, the top layer corresponded to a layer of neutral stability. We perform a two-dimensional numerical simulation of the evolution of cirrus anvil to examine particle sorting processes via radiatively induced cloud-scale circulations.