National Aeronautics and Space Administration

Publication Abstracts

Mülmenstädt et al. 2024, accepted

Mülmenstädt, J., A.S. Ackerman, A.M. Fridlind, M. Huang, P.-L. Ma, N. Mahfouz, S.E. Bauer, S.M. Burrows, M.W. Christensen, S. Dipu, A. Gettelman, L.R. Leung, F. Tornow, J. Quaas, A.C. Varble, H. Wang, K. Zhang, and Y. Zheng, 2024: Can GCMs represent cloud adjustments to aerosol-cloud interactions? Atmos. Chem. Phys., accepted.

General circulation models (GCMs), unlike other lines of evidence, indicate that anthropogenic aerosols cause a global-mean increase in cloud liquid water path (𝓛), and thus a negative adjustment to radiative forcing of the climate by aerosol-cloud interactions. In part 1 of this manuscript series, we showed that this is true even in models that reproduce the negative correlation observed in present-day internal variability of 𝓛 and cloud droplet number concentration (N_d). We studied several possible confounding mechanisms that could explain the noncausal clouds-aerosol correlations in GCMs and that possibly contaminate observational estimates of radiative adjustments. Here, we perform single-column and full-atmosphere GCM experiments to investigate the causal model-physics mechanisms underlying the model radiative adjustment estimate. We find that both aerosols-cloud interaction mechanisms thought to be operating in real clouds — precipitation suppression and entrainment evaporation enhancement — are active in GCMs and behave qualitatively in agreement with physical process understanding. However, the modeled entrainment enhancement has a negligible global-mean effect. This raises the question whether the GCM estimate is incorrect due to parametric or base-state representation errors, or whether the process understanding gleaned from a limited set of canonical cloud cases is insufficiently representative of the diversity of clouds in the real climate. Regardless, even at limited resolution, the GCM physics appears able to parameterize the small-scale microphysics-turbulence interplay responsible for the entrainment enhancement mechanism. We suggest ways to resolve tension between current and future (storm-resolving) global modeling systems and other lines of evidence in synthesis climate projections.

• View preprint on EGUsphere.
• Please note that linked preprint is probably not the final, accepted text.

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@unpublished{mu06200a,
  author={Mülmenstädt, J. and Ackerman, A. S. and Fridlind, A. M. and Huang, M. and Ma, P.-L. and Mahfouz, N. and Bauer, S. E. and Burrows, S. M. and Christensen, M. W. and Dipu, S. and Gettelman, A. and Leung, L. R. and Tornow, F. and Quaas, J. and Varble, A. C. and Wang, H. and Zhang, K. and Zheng, Y.},
  title={Can GCMs represent cloud adjustments to aerosol-cloud interactions?},
  year={2024},
  journal={Atmospheric Chemistry and Physics},
}

TY  - INPR
ID  - mu06200a
AU  - Mülmenstädt, J.
AU  - Ackerman, A. S.
AU  - Fridlind, A. M.
AU  - Huang, M.
AU  - Ma, P.-L.
AU  - Mahfouz, N.
AU  - Bauer, S. E.
AU  - Burrows, S. M.
AU  - Christensen, M. W.
AU  - Dipu, S.
AU  - Gettelman, A.
AU  - Leung, L. R.
AU  - Tornow, F.
AU  - Quaas, J.
AU  - Varble, A. C.
AU  - Wang, H.
AU  - Zhang, K.
AU  - Zheng, Y.
PY  - 2024
TI  - Can GCMs represent cloud adjustments to aerosol-cloud interactions?
JA  - Atmos. Chem. Phys.
JO  - Atmospheric Chemistry and Physics
ER  -

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