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Aiko Voigt, Nicole Albern, and Georgios Papavasileiou

calculations are done for 15 years for the MPI-ESM model with interactive SST, and for at least 5 years for all models with prescribed SST. The partial-radiative perturbation calculations are done with the models’ own radiative transfer schemes. The same diagnostic was used in the aquaplanet work of Voigt and Shaw (2016) , who used the term “cloud-radiative forcing.” For better clarity, we here instead use the term “changes in cloud-radiative heating.” 3. The total cloud-radiative impact and the

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Bjorn Stevens and Stephanie Fiedler

more pristine atmosphere is more susceptible to anthropogenic forcing from aerosol–cloud interactions ( Boucher and Pham 2002 ; Carslaw et al. 2013 ). This staple of aerosol research is formally incorporated in S15 ’s model, which constructs from two terms: one that is linear in emissions, consistent with understanding of aerosol–radiation interactions (whose forcing we denote by ), and the other logarithmic in emissions, consistent with understanding of aerosol–cloud interactions, whose

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Katinka Bellomo, Amy C. Clement, Thorsten Mauritsen, Gaby Rädel, and Bjorn Stevens

radiative forcing influence the variability of Atlantic Niño? b. Role of cloud feedbacks over the Namibian region To investigate the role of cloud feedbacks on Atlantic Niño and large-scale modes of climate variability, we run model experiments in which we enhance positive cloud feedback over the Namibian region, as outlined in section 2 . Differently from observations, cloud feedback is estimated in model simulations as the regression of net CRE at the surface on local SST anomalies. This definition

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Jan Kretzschmar, Marc Salzmann, Johannes Mülmenstädt, Olivier Boucher, and Johannes Quaas

forcing shows more spatial and temporal fluctuations. Based on process considerations, S15 develops a simple, zero-dimensional model for the global-mean aerosol forcing that combines a linear scaling of anthropogenic global-mean sulfur dioxide emissions to represent the radiative forcing (RF) due to aerosol–radiation interactions and a logarithmic scaling of the same quantity to represent the RF due to aerosol–cloud interactions. The logarithmic contribution is of large importance for the constraint

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Angela Benedetti and Marta Janisková

cloud optical depths were compared to sets of different independent observations. Figure 15 shows some of the results for the shortwave and longwave cloud forcings (SWCF and LWCF, respectively) at the top of atmosphere (TOA) and for precipitation averaged over the tropical belt between 20°N and 20°S for April 2006. The TOA radiative forcings obtained from the model runs were compared against the Clouds and the Earth’s Radiant Energy System (CERES) products ( Wielicki et al. 1996 ). The surface

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Dagmar Fläschner, Thorsten Mauritsen, Bjorn Stevens, and Sandrine Bony

, and C. Hohenegger , 2017 : Imprint of the convective parameterization and sea-surface temperature on large-scale convective self-aggregation . J. Adv. Model. Earth Syst. , 9 , 1488 – 1505 , https://doi.org/10.1002/2016MS000865 . 10.1002/2016MS000865 Bergman , J. W. , and H. H. Hendon , 2000 : Cloud radiative forcing of the low-latitude tropospheric circulation: Linear calculations . J. Atmos. Sci. , 57 , 2225 – 2245 , https://doi.org/10.1175/1520-0469(2000)057<2225:CRFOTL>2.0.CO

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Mitchell W. Moncrieff and Changhai Liu

conditions, and large-scale forcing. Cloud microphysics is represented by the NASA Goddard scheme ( Tao et al. 1993 ). The radiative transfer parameterization activated every 15 minutes interacts with cloud, clear atmosphere, and the land surface ( Dudhia 1996 ). Planetary boundary layer physics is represented by the scheme used in the National Centers for Environmental Prediction (NCEP) Medium-Range Forecast (MRF) model ( Hong and Pan 1996 ). It is coupled with a five-layer soil model from which the

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Michael G. Bosilovich, Franklin R. Robertson, and Paul W. Stackhouse

; Trenberth et al. 2002 ; Alexander et al. 2009 ). Relative to El Niño local SST warming and tropical convection, remote oceanic regions of descending motion show reductions in clouds and increasing surface radiative forcing, predominantly from the shortwave ( Stephens et al. 2018 ). In the case of El Niño, warming in the eastern and central equatorial Pacific precedes broader remote ocean warming ( Klein et al. 1999 ; Yu and Rienecker 1999 ; Alexander et al. 2002 ; Mayer et al. 2013 ). Tropospheric

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Aiko Voigt, Bjorn Stevens, Jürgen Bader, and Thorsten Mauritsen

Climate. Cambridge University Press, 680 pp . Ramanathan , V. , 1987 : The role of Earth radiation budget studies in climate and general circulation research . J. Geophys. Res. , 92 ( D4 ), 4075 – 4095 . Ramanathan , V. , R. D. Cess , E. F. Harrison , P. Minnis , B. R. Barkstrom , E. Ahmad , and D. Hartmann , 1989 : Cloud-radiative forcing and climate: Results from the Earth Radiation Budget Experiment . Science , 243 , 57 – 63 . Stevens , B. , and S. E. Schwartz

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Krzysztof M. Markowicz and Marcin L. Witek

cloudiness” ( Sausen et al. 2005 ). The climate effect in terms of the radiative forcing of contrail clouds is highly uncertain because of a limited number of observed statistics of contrail parameters (e.g., Palikonda et al. 2005 ) and difficulties with the parameterization of contrails in general circulation models ( Ponater et al. 2002 ; Rap et al. 2010 ; Kärcher et al. (2010) . The Intergovernmental Panel on Climate Change (IPCC) “Aviation and Global Atmosphere” special report ( Penner et al. 1999

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