6.4 Evidence for Impeded Breakup of Decoupled Precipitating Marine Stratocumulus

Tuesday, 10 July 2018: 11:15 AM
Regency D (Hyatt Regency Vancouver)
Tom goren, University of Leipzig, Leipzig, Germany; and D. Rosenfeld, O. Sourdeval, and J. Quaas

Transitions between marine Stratocumulus cloud (MSC) regimes of open and closed cells are important to the climate system due to the large difference in cloud cover and the subsequent radiative effect. Past studies have supported the claim that when closed-cells start to precipitate significantly they breakup to open cells. Challenging this argument, we show that clouds decoupled from the ocean surface are less likely to breakup, even if they precipitate. This is supported by observations, showing that the difference in cloud cover between coupled and decoupled clouds is the largest when the heaviest rainfall occurs. To demonstrate this, a novel satellite-based methodology for retrieving decoupling degree of MSC was developed. It is hypothesized that gust fronts from precipitation-driven downdrafts collide with each other and trigger convective elements that breakup the cloud layer when clouds are coupled to the ocean surface. This is less likely to occur in precipitating decoupled clouds.
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