Measurements from Michigan Tech's turbulent mixing chamber (the Pi Chamber), show that, in the presence of turbulent fluctuations, the correspondence between size and activation is no longer sharp. In our experiments, the chemical composition of all aerosol is the same, so the diameters of the particles determine the critical supersaturations required for activation. We create steady-state, turbulent cloud conditions and compare the distribution of interstitial aerosol to the distribution of cloud droplet residuals. (The residuals are measured using a pumped counterflow virtual impactor (CVI).) That comparison shows that some aerosol particles are just as likely to remain as interstitial as they are to be activated, a result of fluctuations in the saturation ratio. The comparison of cloud droplet residuals and interstitials also allows us to place bounds on the quasi-steady state supersaturation in the chamber, by identifying the diameter at which particles no longer appear in the droplet residuals, but do appear in the interstitials. Complementary measurements of temperature and water vapor concentration support those general observations.
Chandrakar, K. K., Cantrell, W., Ciochetto, D., Karki, S., Kinney, G., & Shaw, R. A. (2017). Aerosol removal and cloud collapse accelerated by supersaturation fluctuations in turbulence. Geophys. Res. Lett., 44(9), 4359-4367.
Verheggen, B., Cozic, J., Weingartner, E., Bower, K., Mertes, S., Connolly, P., Gallagher, M., Flynn, M., & Baltensperger, U. (2007). Aerosol partitioning between the interstitial and the condensed phase in mixed‐phase clouds. J. Geophys. Res., 112(D23), doi:10.1029/2007JD008714