Observed impact of meso-scale vertical motion on cloudiness

We use estimates of mesoscale vertical velocity and collocated cloud measurements from the second Next-Generation Aircraft Remote Sensing for Validation campaign (NARVAL2) in the tropical North Atlantic to show theobserved impact of mesoscale vertical motion on tropical clouds. Our results not only confirm previously untestedhypotheses about the role of dynamics being nonnegligible in determining cloudiness, but go further to show that at themesoscale, the dynamics has a more dominant control on cloudiness variability than thermodynamics. A simple mass-flux estimate reveals that mesoscale vertical velocity at the subcloud-layer top explains much of the variations in peakshallow cumulus cloud fraction. In contrast, we find that thermodynamic cloud-controlling factors, such as humidity andstability, are unable to explain the variations in cloudiness at the mesoscale. Thus, capturing the observed variability ofcloudiness may require not only a consideration of thermodynamic factors, but also dynamic ones such as the mesoscalevertical velocity