Preprints
https://doi.org/10.5194/acp-2021-360
https://doi.org/10.5194/acp-2021-360

  17 May 2021

17 May 2021

Review status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

Hemispheric contrasts in ice formation in stratiform mixed-phase clouds: Disentangling the role of aerosol and dynamics with ground-based remote sensing

Martin Radenz1, Johannes Bühl1, Patric Seifert1, Holger Baars1, Ronny Engelmann1, Boris Barja González2, Rodanthi-Elisabeth Mamouri3,4, Félix Zamorano2, and Albert Ansmann1 Martin Radenz et al.
  • 1Leibniz Institute for Tropospheric Research (TROPOS), Leipzig, Germany
  • 2Atmospheric Research Laboratory, University of Magallanes, Punta Arenas, Chile
  • 3Department of Civil Engineering and Geomatics, Cyprus University of Technology of Technology, Limassol, Cyprus
  • 4ERATOSTHENES Centre of Excellence, Limassol, Cyprus

Abstract. Multi-year ground-based remote-sensing datasets acquired with the Leipzig Aerosol and Cloud Remote Observations System (LACROS) at three sites: a highly polluted central European site (Leipzig, Germany), a polluted and strongly dust-influenced eastern Mediterranean site (Limassol, Cyprus), and a clean marine site in the southern mid-latitudes (Punta Arenas, Chile) are used to contrast ice formation in shallow stratiform liquid clouds. These unique, long-term datasets at key sites of aerosol-cloud interaction provide a deeper insight into cloud microphysics. The influence of temperature, aerosol load, boundary-layer coupling and gravity wave motion on ice formation is investigated. With respect to previous studies of regional contrasts in the properties of mixed-phase clouds our study contributes the following new aspects: (1) Sampling aerosol optical parameters as a function of temperature, the average backscatter coefficient at supercooled temperatures is within a factor of 3 at all three sites. (2) Ice formation was found to be more frequent for cloud layers with cloud top temperatures above −15 °C than indicated by prior lidar-only studies at all sites. A virtual lidar-detection threshold of IWC needs to be considered in order to bring radar-lidar-based studies in agreement with lidar-only studies. (3) At similar temperatures, cloud layers which are coupled to the aerosol-laden boundary layer show more intense ice formation than de-coupled clouds. (4) Liquid layers formed by gravity waves were found to bias the phase occurrence statistics below −15 °C. By applying a novel gravity wave detection approach using vertical velocity observations within the liquid-dominated cloud top, wave clouds can be classified and excluded from the statistics. After considering boundary layer and gravity-wave influences, Punta Arenas shows lower fractions of ice containing clouds by 0.1 to 0.4 absolute difference at temperatures between −24 and −8 °C. These differences are potentially caused by the contrast in the INP reservoir between the different sites.

Martin Radenz et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-360', Anonymous Referee #1, 14 Jun 2021
    • AC1: 'Reply on RC1 and RC2', Martin Radenz, 30 Sep 2021
  • RC2: 'Comment on acp-2021-360', Anonymous Referee #2, 15 Jun 2021
    • AC1: 'Reply on RC1 and RC2', Martin Radenz, 30 Sep 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-360', Anonymous Referee #1, 14 Jun 2021
    • AC1: 'Reply on RC1 and RC2', Martin Radenz, 30 Sep 2021
  • RC2: 'Comment on acp-2021-360', Anonymous Referee #2, 15 Jun 2021
    • AC1: 'Reply on RC1 and RC2', Martin Radenz, 30 Sep 2021

Martin Radenz et al.

Martin Radenz et al.

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Latest update: 22 Oct 2021
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Short summary
This study brings together long-term ground-based remote sensing observations of mixed-phase clouds at three key locations of aerosol-cloud interactions in the northern and southern hemisphere mid-latitudes. The findings contribute several new aspects on the nature of the excess of supercooled liquid clouds in the southern hemisphere, such as a long-term lidar-based estimate of ice nucleating particle profiles as well as the effects of boundary layer coupling and gravity waves on ice formation.
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