Morphological cellular analysis of Pockets of Open Cells on Marine Stratocumulus fields

More of Earth’s surface is covered by stratocumulus clouds (Sc) than by any other cloud type, making Sc particularly important for Earth’s energy balance, primarily through the reflection of incoming solar radiation. However, representing Sc and their radiative impacts remains one of the greatest challenges for global climate modeling as models cannot resolve the length scale of the processes involved in its formation and evolution. For this reason, Sc represent a major source of uncertainty in climate projections (Wood 2012).

The challenge becomes more complicated due to the organizational complexity exhibited by Sc across a broad range of spatial scales. In particular, marine Sc fields display characteristic mesoscale patterns that can exhibit both organized and disorganized structures. Among these morphological regimes, cellular convection has received particular attention as cloud decks can self-organize into semi-regular tessellations composed of closed and open convective cellular fields.

Here we analyze satellite imagery of Sc organizing into low-reflectivity regions of open cells embedded within closed cellular cloud fields, known as "pockets of open cells" (POCs) (Stevens et al. 2005). We first track POCs from the time they emerge to when they dissipate. Second, a cell-scale analysis is performed for convective fields both inside and outside the POC boundaries to characterize the interface between POC and non-POC regions.

We propose a segmentation, tracking, and morphological analysis of cell geometry and dynamics in both closed and open cellular fields, with particular emphasis on the interactions between these cell types during POC development. A statistical analysis of multiple POCs is conducted to characterize the temporal and spatial contributions of cellular structural and kinetic changes to POC evolution, incorporating the local dynamics between individual cells (Farrell et al. 2017).

Using this framework, key differences between open and closed cellular regimes are identified based on velocity dynamics and morphological evolution. 
Whereas closed cells exhibit relatively slow dynamics, open cells continuously rearrange, changing both size and shape, and display significant cellular mobility, revealing motion flows within the POC region.

Finally, shallow cold pools within POCs are identified based on their lifetime, area expansion, and interactions between neighboring cells. These cold pools, which result from stratiform precipitation from open cells, play a dominant role in the dynamics of open cell fields.

The primary result of this analysis reveals a previously unreported regime of collective cellular dynamics, in which the emergence and evolution of convective organization is strongly influenced by cold pools, exhibiting structural and dynamical behaviors not observed in other known cellular systems.