Lagrangian and Eulerian supersaturation statistics in turbulent cloudy Rayleigh-Bénard convection: Applications for LES subgrid modeling

Although supersaturation has autocorrelation and structure functions similar to the independent scalars (temperature and water vapor), the autocorrela-tion time scale of supersaturation differs. Relative scalar fluxes in DNS without cloud make supersaturation PDFs less skewed than the adiabatic case, where they are highly negatively skewed. However, droplet condensation changes the PDF shape response: it becomes positively skewed for the adiabatic case and negatively skewed when the sidewall relative fluxes are large.

Condensation also increases correlations between water vapor and temperature in the presence of relative scalar fluxes but decreases correlations for the adiabatic case. These changes in correlation suppress supersaturation variability for the nonadiabatic cases and increase it for the adiabatic case. Implications of this work for subgrid microphysics model-ing using a Lagrangian stochastic scheme are also discussed.