Preprints
https://doi.org/10.5194/egusphere-2023-2600
https://doi.org/10.5194/egusphere-2023-2600
05 Dec 2023
 | 05 Dec 2023

Contribution of fluorescent primary biological aerosol particles to low-level Arctic cloud residuals

Gabriel Pereira Freitas, Ben Kopec, Kouji Adachi, Radovan Krejci, Dominic Heslin-Rees, Karl Espen Yttri, Alun Hubbard, Jeffrey M. Welker, and Paul Zieger

Abstract. Mixed-phase clouds (MPC) are key players in the Arctic climate system due to their role in modulating solar and terrestrial radiation. Such radiative interactions critically rely on the ice content of MPC which, in turn, also depend on the availability of ice nucleating particles (INP). INP sources and concentrations are poorly understood in the Arctic. Recently, INP active at high temperatures were associated with the presence of primary biological aerosol particles (PBAP). Here, we investigated for a full year the abundance and variability of fluorescent PBAP (fPBAP) within cloud residuals, directly sampled by a multiparameter bioaerosol spectrometer coupled to a ground-based counterflow virtual impactor inlet at the Zeppelin Observatory (475 m asl), Ny-Ålesund, Svalbard. fPBAP concentrations (10-3–10-2 L-1) and contributions to coarse-mode aerosol (0.1 to 1 in every 103 particles) within cloud residuals were found to be close to those expected for concentrations of high-temperature INP. Transmission electron microscopy also confirmed the presence of fPBAP, most likely bacteria, within the cloud residual samples. Seasonally, our results reveal an elevated presence of fPBAP within cloud residuals in summer. Parallel water vapor isotope measurements point towards a link between summer clouds and regionally sourced air masses. Low-level MPC were predominantly observed at the beginning and end of summer, and one explanation for their presence is the existence of high-temperature INP. In this study, we present observational evidence that fPBAP may play an important role in determining the phase of low-level Arctic clouds. These findings have potential implications for the future description of sources of cloud condensation nuclei given ongoing changes in the hydrological and biogeochemical cycles that will influence the PBAP flux in and towards the Arctic.

Gabriel Pereira Freitas, Ben Kopec, Kouji Adachi, Radovan Krejci, Dominic Heslin-Rees, Karl Espen Yttri, Alun Hubbard, Jeffrey M. Welker, and Paul Zieger

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2600', Anonymous Referee #1, 20 Dec 2023
  • RC2: 'Comment on egusphere-2023-2600', Anonymous Referee #2, 31 Jan 2024
Gabriel Pereira Freitas, Ben Kopec, Kouji Adachi, Radovan Krejci, Dominic Heslin-Rees, Karl Espen Yttri, Alun Hubbard, Jeffrey M. Welker, and Paul Zieger
Gabriel Pereira Freitas, Ben Kopec, Kouji Adachi, Radovan Krejci, Dominic Heslin-Rees, Karl Espen Yttri, Alun Hubbard, Jeffrey M. Welker, and Paul Zieger

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Short summary
Bioaerosols can participate in ice formation within clouds. In the Arctic, where global warming manifests most, they may become increasingly more important as their sources are prevailing for a longer period of the year. We have directly measured bioaerosols within clouds for a full year at an Arctic mountain site using a novel combination of cloud particle sampling and single-particle techniques. We show that bioaerosols act as cloud seeds and may influence the presence of ice within clouds.