Research Projects

Clouds are an aggregate of water droplets/ice crystals floating in the atmosphere. The atmospheric clouds not only play a significant role in the hydrological cycle but are also crucial for maintaining the earth's radiation budget as they absorb longwave radiation and reflect short-wave solar radiation. Thus, it is important to have a thorough understanding of the microphysics of cloud formation for accurate prediction of future climate systems. The mechanisms involved in the warm rain initiation are the origin of cloud droplets by nucleation, followed by their growth due to condensation and collision-coalescence process. The role of the condensation process in the growth of cloud drops into raindrops is minimal due to the unavailability of required supersaturation. Another phenomenon that is helpful in the growth of cloud droplets is collision and coalescence. Due to turbulence, cloud droplets collide and change their electric charge in warm clouds. Drops with opposing charges will attract each other, merge, and grow until they fall. Collision rates in the cloud depend on the droplet size and turbulence properties in which these droplets reside. The growth of these droplets because of collision and coalescence is not well understood yet, which is the focus of the present study. The atmospheric turbulence helps in the growth of condensation drops and shortens the time for raindrop formation. To fully understand cloud physics, it is crucial to understand the role of turbulence on cloud droplets' rate of collision and coalescence. Various numerical studies have been conducted to understand the interaction of cloud droplets with turbulent flows. However, there are a lot of challenges associated with these techniques; for example, the DNS study of droplet growth in turbulence in parameter ranges relevant to atmospheric clouds requires very large computational efforts because of the very high Reynolds number. We can overcome these challenges through the experimental study of this problem, due to the better control of the relevant parameters at a higher equivalent Reynolds number. There are a handful of experimental studies on droplet growth for parameter ranges relevant to atmospheric clouds. Thus, the present research is focused on experimentally studying the interaction of vortical structures with droplets to better understand the dominant growth of the droplet due to turbulence after a certain threshold diameter. The growth would be the function of eddy size & its distribution, strength & life cycle of the eddy, and initial droplet size & number distribution. This interaction will be studied with an idealized vortical structure say a vortex ring and we will use the state of art measurement to understand this interaction. We will then study the interaction of droplets with turbulence relevant to ABL and methods like time-resolved multiphase PIV and PTV will be utilized for studying the complexity of clustering and collision in clouds.