Do observations support ideas behind common mass flux closures?

Determining the mass flux at cloud base is the principle closure needed in convective parameterizations. Here we evaluate if observations from the EUREC⁴A field campaign support ideas behind common shallow-convective mass flux closures. All parameters of the closures are diagnosed at the mesoscale (200km, 3h) from dropsonde data and turbulence measurements. The closure models are compared to a reference mass flux estimated as a residual of the sub-cloud layer mass budget from the same circular dropsonde arrays. We find that a closure using the subcloud convective velocity scale (w_*) captures the magnitude but underestimates the variability of the reference mass flux. A closure using a  turbulence kinetic energy (TKE) based velocity scale instead explains 78% of mass flux variability. These results suggest that (1) the full TKE needs to be considered rather than just the convective contribution represented by w_*, and (2) the TKE may contain information about the area fraction of thermals, which makes a separate cloud area fraction scale unnecessary to explain mass flux variability during EUREC⁴A.