Mysterious Marine Stratocumulus

Abstract:

Marine low clouds are important to climate. The difficulties global climate models have in representing the areal extent and temporal variability of these clouds has motivated numerous observational and modeling studies over the last two decades. New observations have challenged accepted explanations for the underlying physical mechanisms that modulate marine stratocumulus. Recent work has revised thinking on the relative importance of feedbacks among aerosols, microphysics, dynamics and radiation. This presentation will showcase some new observational findings of marine stratocumulus that do not fit current theories. For example, data reveal: large multi-day (3-50 days) variability of cloud amount; mesoscale spatial patterns of drizzle cells that are remarkably static for more than 2 hours; individual drizzle cells lifetimes that exceed 2 times the rainout timescale; and shallow clouds < 500 m thick that generate intense rainfall (> 38 dBZ). Further, what potential mechanisms explain why the seasonal variation in the diurnal cycle of regional cloudiness shows the greatest variation in the southeast Atlantic and least in the northeast Pacific? These observations point the way for potential new research that may inspire a more comprehensive physical understanding of marine stratocumulus clouds.