Subtropical marine low clouds have been widely studied over the last few decades, since they were identified as the main contributors in uncertainty in cloud climate feedback. As a result numerous studies with turbulence models and emergent constraints from climate model simulations have provided evidence the the cooling cloud radiative effect (CRE) of clouds weakens with warming: a positive low-cloud feedback. These studies and insights have contributed to a reduction in the overall uncertainty in climate feedback.

However in none of these studies potential effects of mesoscale organisation of these low clouds are taken into account. Most of the high resolution turbulence resolving simulation studies that have informed our understanding of low-cloud feedback did not incorporate any mesoscale variability and organisation. Yet on the other hand observations show that mesoscale organisation of the low tradewind clouds are the rule rather than the exception.

In this colloquium I will mainly ask and discuss a number of questions that emerge from this. How do we define mesoscale organisation? What causes the different modes of mesoscale organisation? How well can we observe and simulate mesoscale organisation and to what extent does it matter for cloud climate feedback?