Preprints
https://doi.org/10.5194/egusphere-2023-2773
https://doi.org/10.5194/egusphere-2023-2773
23 Nov 2023
 | 23 Nov 2023

A cloud-by-cloud approach for studying aerosol-cloud interaction in satellite observations

Fani Alexandri, Felix Müller, Goutam Choudhury, Peggy Achtert, Torsten Seelig, and Matthias Tesche

Abstract. The effective radiative forcing (ERF) due to aerosol-cloud interactions (ACI) and rapid adjustments (ERFaci) still causes the largest uncertainty in the assessment of climate change. It is understood only with medium confidence and studied primarily for warm clouds. Here, we present a novel cloud-by-cloud (C×C) approach for studying ACI in satellite observations that combines the concentration of cloud condensation nuclei (nCCN) and ice nucleating particles (nINP) from polar-orbiting lidar measurements with the development of the properties of individual clouds from tracking them in geostationary observations. We present a step-by-step description for obtaining matched aerosol-cloud cases. The application to satellite observations over Central Europe and Northern Africa during 2014 together with rigorous quality assurance leads to 399 liquid-only clouds and 95 ice-containing clouds that can be matched to surrounding nCCN and nINP, respectively, at cloud level. We use this initial data set for assessing the impact of changes in cloud-relevant aerosol concentrations on the cloud droplet number concentration (Nd) and effective radius (reff) of liquid clouds and the phase of clouds in the regime of heterogeneous ice formation. We find a Δ ln Nd/Δ ln nCCN of 0.13 to 0.30 which is at the lower end of commonly inferred values of 0.3 to 0.8. The Δ ln reff/Δ ln nCCN between -0.09 and -0.21 suggests that reff decreases by -0.81 to -3.78 nm per increase in nCCN of 1 cm-3. We also find a tendency towards more cloud ice and more fully glaciated clouds with increasing nINP that cannot be explained by the increasingly lower cloud-top temperature of super-cooled liquid, mixed-phase, and fully glaciated clouds alone. Applied to a larger amount of observations, the C×C approach has the potential to enable the systematic investigation of warm and cold clouds. This marks a step change in the quantification of ERFaci from space.

Fani Alexandri, Felix Müller, Goutam Choudhury, Peggy Achtert, Torsten Seelig, and Matthias Tesche

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2773', Anonymous Referee #1, 09 Dec 2023
    • AC1: 'Comment on egusphere-2023-2773', Matthias Tesche, 12 Feb 2024
  • RC2: 'Comment on egusphere-2023-2773', Anonymous Referee #2, 02 Feb 2024
    • AC1: 'Comment on egusphere-2023-2773', Matthias Tesche, 12 Feb 2024
  • AC1: 'Comment on egusphere-2023-2773', Matthias Tesche, 12 Feb 2024

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2773', Anonymous Referee #1, 09 Dec 2023
    • AC1: 'Comment on egusphere-2023-2773', Matthias Tesche, 12 Feb 2024
  • RC2: 'Comment on egusphere-2023-2773', Anonymous Referee #2, 02 Feb 2024
    • AC1: 'Comment on egusphere-2023-2773', Matthias Tesche, 12 Feb 2024
  • AC1: 'Comment on egusphere-2023-2773', Matthias Tesche, 12 Feb 2024
Fani Alexandri, Felix Müller, Goutam Choudhury, Peggy Achtert, Torsten Seelig, and Matthias Tesche

Video abstract

Video abstract As per end credits https://speicherwolke.uni-leipzig.de/index.php/s/3yQ7K7D7ZmqgNBk

Fani Alexandri, Felix Müller, Goutam Choudhury, Peggy Achtert, Torsten Seelig, and Matthias Tesche

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Short summary
We present a novel method for studying aerosol-cloud interactions. It combines cloud-relevant aerosol concentrations from polar-orbiting lidar observations with the development of individual clouds from geostationary observations. Application to one year of data gives first results on the impact of aerosols on the concentration and size of cloud droplets and on cloud phase in the regime of heterogeneous ice formation. The method could enable the systematic investigation of warm and cold clouds.