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What favors convective aggregation and why?

Abstract : The organization of convection is ubiquitous, but its physical understanding remains limited. One particular type of organization is the spatial self-aggregation of convection, taking the form of cloud clusters, or tropical cyclones in the presence of rotation. We show that several physical processes can give rise to self-aggregation and highlight the key features responsible for it, using idealized simulations. Longwave radiative feedbacks yield a radiative aggregation. In that case, sufficient spatial variability of radiative cooling rates yields a low-level circulation, which induces the upgradient energy transport and radiative-convective instability. Not only do vertically integrated radiative budgets matter but the vertical profile of cooling is also crucial. Convective aggregation is facilitated when downdrafts below clouds are weak (moisture-memory aggregation), and this is sufficient to trigger aggregation in the absence of longwave radiative feedbacks. These results shed some light on the sensitivity of self-aggregation to various parameters, including resolution or domain size.
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Submitted on : Monday, August 31, 2015 - 9:25:43 AM
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Caroline Muller, Sandrine Bony. What favors convective aggregation and why?. Geophysical Research Letters, 2015, 42 (13), pp.5626-5634. ⟨10.1002/2015GL064260⟩. ⟨hal-01187680⟩



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