Abstract
Abstract. We simulate the aerosol–cloud–precipitation system as a collection of cloud elements, each coupled through physically based interactions with adjacent clouds. The equations describing the individual clouds follow from the predator–prey model of Koren and Feingold (2011) with the addition of coupling terms that derive from the flow of air between the components resulting from surface divergence or convergence of flows associated with the life cycle of an individual cell. It is shown that some degree of coupling might stabilize clouds that would ordinarily become unstable. Varying the degree of coupling strength has significant influence on the system. For weak coupling, the clouds behave as independent oscillators with little influence on one another. As the local coupling strength increases, a point is reached at which the system becomes highly synchronized, similar to the Sakaguchi et al. (1987) model. Individual cloud oscillators in close proximity to one another can be both in-phase or out-of-phase depending on the choice of the time constant for the delay in communication between components. For the case considered, further increases in coupling strength result in reduced order and eventually unstable growth. Finally it is demonstrated that the set of coupled oscillators mimics qualitatively the spatial structure and synchronized behaviour of both closed and open-cellular cloud fields observed in satellite imagery, and produced by numerically intensive large eddy simulation.
Highlights
The study of weather and clouds can most certainly be traced back to prehistoric times; there is ample evidence that our ancestors were keen observers of clouds, rain, and other atmospheric phenomena of immediate concern for survival
We focus on larger values of τc since these are likely more relevant to boundary layer cloud systems exhibiting mesoscale cellular convection. (Shorter, variable coupling times are more appropriate to cumulus cloud fields and will be explored in later work.)
We have extended the predator–prey equations for the aerosol–cloud–precipitation system first presented by Koren and Feingold (2011) to individual subcomponents of the system and shown how solutions to the coupled system of equations act in ways that mimic some of the characteristics and spatial patterns developed by computationally intensive large eddy simulation and observed by satellite imagery
Summary
The study of weather and clouds can most certainly be traced back to prehistoric times; there is ample evidence that our ancestors were keen observers of clouds, rain, and other atmospheric phenomena of immediate concern for survival. Rather than address weather patterns, this paper concerns itself with commonly observed patterns in cloud systems on scales of O(10–1000 km). The motivation of this study is to show that cloud systems often organize in ways that are common to other natural systems. It addresses the phenomenon of synchronization within cloud systems. When the components of the system are sufficiently well coupled, synchronization can result in fascinating cloud patterns that constantly regenerate themselves (Feingold et al, 2010; Koren and Feingold, 2011, 2013) and are quite resilient to perturbation
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