Abstract: In this paper, we propose a method for the simulation of clouds using particles exclusively. The method is based on position based fluids, which simulates fluids using position constraints. To reduce the simulation time, we have used adaptive splitting and merging to concentrate computation on regions where it is most needed. When clouds are formed, particles are split so as to add more details to the generated cloud surface and when they disappear, particles are merged back. We implement our adaptive method on the Graphics Processing Unit (GPU) to accelerate the computation. While the splitting portion is easily parallelizable, the merge portion is not. We develop a simple algorithm to address this problem and achieve reasonable simulation times. Copyright 2015 John Wiley & Sons, Ltd.