naa a22 4500 530098326 20181026074613.0 cr unu---uuuuu 181026s2014 xx s 000 0 eng 10.3929/ethz-b-000093748 doi 10.5194/acp-14-11997-2014 doi (ETHRESEARCH)oai:www.research-collection.ethz.ch:20.500.11850/93748 Impact of the representation of marine stratocumulus clouds on the anthropogenic aerosol effect [Elektronische Daten] [David Neubauer, Ulrike; id_orcid 0000-0001-8885-3785 Lohmann, Corinna Hoose, Maria G. Frontoso] Atmos. chem. phys. Open access ethresearch Stratocumulus clouds are important for climate as they reflect large amounts of solar radiation back into space. However they are difficult to simulate in global climate models because they form under a sharp inversion and are thin. A comparison of model simulations with the ECHAM6-HAM2 global aerosol climate model to observations, reanalysis and literature data revealed too strong turbulent mixing at the top of stratocumulus clouds and a lack of vertical resolution. Further reasons for cloud biases in stratocumulus regions are the too "active" shallow convection scheme, the cloud cover scheme and possibly too low subsidence rates. To address some of these issues and improve the representation of stratocumulus clouds, we made three distinct changes to ECHAM6-HAM2. With a "sharp" stability function in the turbulent mixing scheme we have observed, similar to previous studies, increases in stratocumulus cloud cover and liquid water path. With an increased vertical resolution in the lower troposphere in ECHAM6-HAM2 the stratocumulus clouds form higher up in the atmosphere and their vertical extent agrees better with reanalysis data. The recently implemented in-cloud aerosol processing in stratiform clouds is used to improve the aerosol representation in the model. Including the improvements also affects the anthropogenic aerosol effect. In-cloud aerosol processing in ECHAM6-HAM2 leads to a decrease in the anthropogenic aerosol effect in the global annual mean from −1.19 Wm−2 in the reference simulation to −1.08 Wm−2, while using a "sharp" stability function leads to an increase to −1.34 Wm−2. The results from the simulations with increased vertical resolution are diverse but increase the anthropogenic aerosol effect to −2.08 Wm−2 at 47 levels and −2.30 Wm−2 at 95 levels. Creative Commons Attribution 3.0 Unported http://creativecommons.org/licenses/by/3.0 ethresearch Neubauer David joint author Lohmann Ulrike; id_orcid 0000-0001-8885-3785 joint author Hoose Corinna joint author Frontoso Maria G. joint author Atmospheric Chemistry and Physics Göttingen : Copernicus 14 (21), pp. 11997-12022 1680-7375 http://hdl.handle.net/20.500.11850/93748 text/html WWW-Backlink auf das Repository (Open access) 1 Journal Article ethresearch ETHRESEARCH 856 40 http://hdl.handle.net/20.500.11850/93748 text/html WWW-Backlink auf das Repository (Open access) ETHRESEARCH 700 1- Neubauer David joint author ETHRESEARCH 700 1- Lohmann Ulrike; id_orcid 0000-0001-8885-3785 joint author ETHRESEARCH 700 1- Hoose Corinna joint author ETHRESEARCH 700 1- Frontoso Maria G. joint author ETHRESEARCH 773 0- Atmospheric Chemistry and Physics Göttingen : Copernicus 14 (21), pp. 11997-12022 1680-7375 BK010053 XK010053 XK010000 ETHRESEARCH ETHRESEARCH ETHRESEARCH Journal Article Open access