Observations of fog-aerosol interactions over central Greenland | CU Experts

Supercooled fogs can have an important radiative impact at the surface; of the Greenland Ice Sheet, but they are difficult to detect and our; understanding of the factors that control their lifetime and radiative; properties is limited by a lack of observations. This study demonstrates; that spectrally resolved measurements of downwelling longwave radiation; can be used to generate retrievals of fog microphysical properties; (phase and particle effective radius) when the fog visible optical depth; is greater than ~0.25. For twelve cases of fog under; otherwise clear skies between June and September 2019 at Summit Station; in central Greenland, nine cases were mixed-phase. The mean ice particle; (optically-equivalent sphere) effective radius was 24.0±7.8 µm, and the; mean liquid droplet effective radius was 14.0±2.7 µm. These results,; combined with measurements of aerosol particle number concentrations,; provide observational evidence supporting the hypotheses that (a) low; surface aerosol particle number concentrations can limit fog liquid; water path, (b) fog can act to increase near-surface aerosol particle; number concentrations through enhanced mixing, and (c) multiple fog; events in quiescent periods gradually deplete near-surface aerosol; particle number concentrations.

VIVO