We find that the simulated stratus cloud is very sensitive to the concentration of ice crystals. Using middle-latitude estimates of the availability of ice nuclei, we find that the concentrations of ice crystals is large enough to result in the almost complete dissipation of otherwise solid, optically-thick stratus layers. A tenuous stratus can be maintained when the continuous input of moisture through large-scale advection is strong enough to balance the ice production. However, only by reducing the concentration of IFN to 0.3 of the original values in association with the large-scale moisture and warm advection, can a persistent, optically thick stratus layer be maintained. The results obtained from the reduced IFN simulation compare reasonably well with observations.
The longwave radiative fluxes at the surface are significantly different between the solid stratus and liquid-water-depleted higher crystal concentration experiments.
This work suggests that transition-season Arctic stratus can be very vulnerable to anthropogenic sources of IFN, which can alter cloud structure sufficiently to affect the rates of melting and freezing of the Arctic ocean