Convective mass flux
From AMS Glossary
convective mass flux
This mass flux Mc is given by
where ρ is air density, σ is fraction of area covered by updrafts, wup is the vertical velocity averaged across all updrafts, and wdown is the vertical velocity averaged over all downdrafts. With the mass flux, one can describe the average turbulent vertical flux of any conserved variable, such as potential temperature θ in cloudless thermals, by
is the vertical kinematic heat flux, θup is the potential temperature averaged across all updrafts, and θdown is the potential temperature averaged across all downdrafts. This method allows population-wide statistics to be described, without needing characteristics of individual updrafts and downdrafts.