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Progress in quantifying the effective radiative forcing due to aerosol-cloud interactions

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Wednesday, 08 January 2020, 12:00

Wednesday, January 8, 2020. 12:00PM. Progress in quantifying the effective radiative forcing due to aerosol-cloud interactions. Johannes Quaas, Leipzig University. Sponsored by NOAA GFDL. More information here


The effective radiative forcing due to aerosol-cloud interaction, ERFaci, is composed of the radiative forcing due to aerosol-cloud interactions, RFaci (Twomey effect) that is the immediate response of cloud albedo to an increase in droplet number concentration, Nd. Previous satellite-based quantifications of this effect were hampered by deficiencies in the retrieval of aerosol and also Nd. The talk will firstly discuss progress in this regard, which leads to a stronger estimated RFaci than previous satellite-based approaches. The other component of ERFaci is in the cloud adjustments. These can be split into adjustments of cloud fraction, f, and liquid water path, L. In terms of the latter, statistical relationships between L and Nd show on average negative adjustments of L (a positive forcing component). In turn, the analysis of ship-, volcano- and industry tracks leads to an estimated small overall effect on L; these results are trustworthy since a cause-effect relation is assured. In terms of the f adjustment, the current results point to an increase in cloud fraction at larger Nd. It is unclear which processes lead to this result. The talk will also briefly discuss how cloud-resolving simulations may help to better understand the remaining uncertainties. In the last part, a brief discussion will be presented on initial steps towards an estimate of the response of cirrus to anthropogenic aerosols.

Location  NOAA GFDL, Smagorinsky Seminar Room, Princeton University, Princeton, NJ