Microphysical Aspects of Cumulus Clouds

在云的视觉识别中，多云空气和环境中的干燥空气之间发生了积极的混合。最近对层积云夹带的观测提供了证据，表明干空气主要是从云顶而不是从横向边界进入。目前，夹带机制尚未完全了解。携带的体积，与较冷和较干燥的空气从上面，稀释了多云的空气，是负浮力，因此在云内下降。根据现场观察和实验室实验，被夹带的空气团的行为被设想为一个球形漩涡，在团的中间有强烈的上升气流，而在外围有缓慢的上升或下降气流。在这项资助下，Telford教授将研究湍流球形涡旋的动力学，并将其应用于云模型中。由于夹带过程可能在解释积云的有限寿命和预测世界各地观测到的各种云滴大小光谱方面发挥重要作用，因此，如果成功验证，特尔福德教授的新理论将对云建模做出重大贡献。

Within the visual identification of clouds, active mixing takes place between the cloudy air and the drier air of its environment. Recent observations of stratocumulus entrainment provide evidence that dry air mostly enters from the cloud top instead of from the lateral boundaries. At present, the entrainment mechanism is not fully understood. The entrained volume, with the cooler and drier air from above, dilutes the cloudy air, is negatively buoyant, and therefore descends within the cloud. Based on field observations and laboratory experiments, the entrained blob of air is envisioned to behave like a spherical vortex, with strong updraft in the middle of the blob and slower rising or descending air around the periphery. Under this grant, Profesor Telford will examine the dynamics of a turbulent spherical vortex and implement it in a cloud model. Since the entrainment processes may play a significant role in explaining the finite life time of cumulus clouds and in predicting various cloud drop size spectra observed around the world, Professor Telford's new theory, if successfully tested, will be a major contribution to cloud modelling.