Comparison of the Transitions of Warm Boundary Layer Clouds between the Four Main Oceanic Basins

The stratocumulus-to-cumulus transition is typically considered to behave similarly between the four major subtropical oceanic basins (northeast Pacific and Atlantic, southeast Pacific and Atlantic). All of the transitions are subject to similar cloud-controlling factors, in particular, changes in sea surface temperature and lower tropospheric stability, but differences between the four basins may also provide insight into cloud dependencies upon other behavioral controls. For example, the northern hemisphere basins allow for a fuller transition into deeper cumuli clouds than do the southern hemisphere basins, because the asymmetrical placement of the inter-tropical convergence zone. Land-atmosphere coupling affects the initial conditions of the transitions in all the basins, but more pronouncedly so for the southern hemisphere basins. This is apparent in differing cloud evolutions between the southern Atlantic and Pacific basins. Differences in the land-atmosphere coupling also affects the range of possible aerosol-cloud interactions. This presentation will seek to provide a useful overview of the similarities and differences between the major planetary subtropical transitions, address the question of how important the differences in the external factors may be to the cloud evolutions, and in doing so will aim to highlight knowledge gaps, if any. Satellite and ERA5 datasets provide the large-scale overview, with data from field campaigns providing more detailed insights.