the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Significant Influence of UV-vis Irradiation on Cloud Activation Efficiencies of Ammonium Sulfate Aerosols under Simulated Chamber Conditions
Abstract. In this work, an optimized protocol to generate an expansion-type liquid clouds with and without UV-visible light irradiation conditions for simulation chamber studies is presented. Sensitivity of the process to key parameters such as initial relative humidities, temperature inhomogeneities, droplets lifetime or seed particle number is illustrated. The obtained clouds have shown that not all seeds particles were always activated and so an iterative numerical method has been re-designed to separate cloud droplets from non-activated seed particles during data analysis allowing the characterization of the cloud droplet formation properties without CCN counter data.
Two types of experiments, clouds without irradiation (N-IC) and under UV-visible light irradiation conditions (IC), have been conducted in the CESAM multiphase atmospheric chamber. Measured cloud droplet lifetimes were in good agreement with atmospheric droplet lifetimes. The achieved supersaturation in the cloud was mostly sensitive to the initial relative humidity in the chamber. The comparison between the cloud formation pattern of N-IC and LC was also investigated. Under illumination conditions, the generated clouds clearly showed a gradual activation of seed particles into droplets and thus of the microphysical properties like LWC and droplet concentration, while under dark conditions, clouds faced a flash activation of seed particles. Because this phenomenon may also impact the air/water partitioning of semi-volatile compounds, and it should be considered for further studies, especially in further multiphase photochemical studies implying water-soluble volatile organic compounds in the CESAM chamber.
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Status: open (until 12 Apr 2024)
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CC1: 'Comment on amt-2023-206', Harry ten Brink, 15 Mar 2024
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-I would like to mention the omission in the list of chamber of the large flow-thru cloud chamber at ECN Petten with extensive performance tests (Khlystov et al. plus PhD thesis)
-The source of the UV radiation is not provided and apparently also heat in the form of IR radiation is provided by the source: this is as indicated absorbed by the water droplets
Are there data on the heat flux so that the heating can indeed be estimated?
Citation: https://doi.org/10.5194/amt-2023-206-CC1 -
CC2: 'Reply on CC1', Jean-Francois Doussin, 22 Mar 2024
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Thank you very much for your interest to our paper and for letting us know.
Indeed our cloud chamber quick overview was more focused on static chambers rather than flow chambers for a better comparison with the CESAM facilty but we will pay attention to mention Petten facility in the final version.
Concerning light source and its UV/IR content : Indeed, it is not described in this paper as it has been largely described and commented in previous CESAM papers (including the original description by Wang et al, 2011). We may consider to add it as supplementary information in the final version if it is considered needed.
Again thank you for helping us to improve the paper
Citation: https://doi.org/10.5194/amt-2023-206-CC2 -
CC3: 'Reply on CC2', Harry ten Brink, 22 Mar 2024
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I suggest to provide brief summary of the UV source plus a comment that it also emits heat radation (IR?) as now given as reason for a different nucleation regime later on
Citation: https://doi.org/10.5194/amt-2023-206-CC3
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CC3: 'Reply on CC2', Harry ten Brink, 22 Mar 2024
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CC2: 'Reply on CC1', Jean-Francois Doussin, 22 Mar 2024
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RC1: 'Comment on amt-2023-206', Anonymous Referee #1, 27 Mar 2024
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The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2023-206/amt-2023-206-RC1-supplement.pdf
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