Arctic aerosol net indirect effects on thin, mid-altitude, liquid-bearing clouds
Lauren M. Zamora1,2, Ralph A. Kahn2, Sabine Eckhardt3, Allison McComiskey4, Patricia Sawamura5,6, Richard Moore5, and Andreas Stohl31NASA Postdoctoral Program Fellow, Universities Space Research Association 2NASA Goddard Space Flight Center, Greenbelt, MD, USA 3NILU - Norwegian Institute for Air Research, Kjeller, Norway 4NOAA Earth System Research Laboratory, Boulder, CO, USA 5NASA Langley Research Center, Hampton, VA, USA 6Science Systems and Applications, Inc., Greenbelt, MD, USA
Received: 21 Nov 2016 – Accepted for review: 13 Dec 2016 – Discussion started: 14 Dec 2016
Abstract. Aerosol indirect effects have uncertain, but potentially large, impacts on the Arctic energy budget. Here, we have reduced uncertainty in current-day Arctic net aerosol indirect effects on the surface by better constraining various physical and microphysical characteristics of optically thin, liquid-containing clouds in clean, average and aerosol-impacted conditions using a combination of CALIPSO and CloudSat data and model output. This work provides a foundation for how future observational studies can evaluate previous model estimates of the aerosol indirect effect. Clouds over sea ice and open ocean show large differences in surface and meteorological forcing, including a near doubling of multi-layer cloud presence over the open ocean compared to sea ice. The optically thin cloud subset is susceptible to aerosols, and over sea ice we estimate a regional scale maximum net indirect effect on these clouds during polar night equivalent to ~ 0.6–0.8 W m−2 at the surface. Aerosol presence is related to reduced precipitation, cloud thickness, and radar reflectivity, and may be associated with an increased likelihood of cloud presence in the liquid phase. The observations are consistent with a thermodynamic indirect effect hypothesis and are inconsistent with a glaciation indirect effect.
Zamora, L. M., Kahn, R. A., Eckhardt, S., McComiskey, A., Sawamura, P., Moore, R., and Stohl, A.: Arctic aerosol net indirect effects on thin, mid-altitude, liquid-bearing clouds, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1037, in review, 2016.