Vertical motions of drops of different sizes in marine stratus and the development of drizzle

Swarndeep Gill, University of Wyoming

Much effort in the past two decades has been put forth to understanding marine stratocumuli and stratus clouds. Both observational and modeling studies have covered scales ranging from the global scale to the scale of cloud microphysics. The attention has been given because of the large impact these clouds have on the earth's albedo, and thus the overall global radiation budget. Stratocumuli and stratus extend over large areas over the earth's oceans with great persistence depending on location and time of year. Modeling these clouds accurately is essential to predicting future climate change. However this has been complicated by the fact that the process that leads to their formation, persistence and even break up occurs on scales too small for Global Climatology Models.

Drizzle in stratiform clouds is of interest not only because of its impact on dynamics, but also because it has important effects on the optical and radiative properties of the cloud; making it an important current topic. An important element in understanding this process is to characterize the spatial and temporal history of drizzle drops. Since simple upward moving parcel descriptions are invalid in stratus, clues can be derived from associating air motions within the cloud to drizzle drops, and cloud droplets of different sizes. Turbulence, and cloud top entrainment instability (CTEI) have effects on the development of drizzle in stratus. Therefore associating cloud variables, such as liquid water content, temperature, and total concentration with vertical velocity are also important. Current analysis and future work will be discussed.