Laboratory Investigations of the Dynamics of Anomalous Entrainment in Cumulus-cloud flows

TL;DR

This paper investigates anomalous entrainment in cumulus clouds through laboratory experiments, providing detailed insights and supporting data to enhance understanding of cloud dynamics and improve parameterization schemes.

Contribution

It offers a comprehensive and detailed account of cumulus-cloud entrainment phenomena, supplementing prior laboratory and modeling studies with new experimental insights.

Findings

Laboratory measurements of 'purity' align with cloud-resolving models.

Insights into homogeneous vs. inhomogeneous mixing in clouds.

Enhanced understanding of entrainment anomalies in cumulus clouds.

Abstract

Anomalous entrainment in cumulus clouds has been a topic of investigation over many decades in the past. Its importance stems from the fact that entrainment rate is one of the major inputs to several cumulus-parameterization schemes. Recently Narasimha et al. (PNAS; 2011) have successfully simulated the large-scale dynamics of cumulus-cloud flows in the laboratory and provided a mechanistic explanation for the observed cumulus-entrainment anomalies. They showed a favourable comparison of a dilution-related quantity (called 'purity') between the laboratory measurements and cloud-resolving-model computations, and discussed the important problem of homogeneous vs. inhomogeneous mixing in cumulus clouds. The main purpose of the present report is to provide additional supporting information and a more detailed account of the entrainment-related issues not included in the PNAS paper due to space constraints. We believe this report, in conjunction with the paper, will present to the reader a comprehensive and more-or-less complete documentation on the issues mentioned above.