A closed-to-open cell mixed-phase cloud transition observed over the Nordic Seas under high aerosol loading and strong surface fluxes

Abstract. Closed-to-open cell mixed-phase cloud transitions within marine cold air outbreaks subjected to strong turbulent surface fluxes remain poorly understood despite their importance to high-latitude climate. The Cold-Air outbreak Experiment in the Sub-Arctic Region (CAESAR) research aircraft sampled closed-cells with cloud condensation nuclei concentrations surpassing 680 cm-3, decreasing to 90 cm-3 across a transition to open-cells. The aerosol likely originated from Siberian industrial emissions. With fetch, liquid water paths (LWPs) increase from 120 g m-2 to 270 g m-2 and cloud-top effective diameters increase from 10 μm to 16 μm, coincident with more riming. Ice particle number concentrations (Ni) are generally 2 L-1 or less, but exceed ice nucleating particle number concentrations by 100x. As the cloud-top inversion weakens and the boundary layer deepens further, ice precipitation co-exists with lidar-observed surface cold pools, modulated by entrainment events, juxtaposed with surface-based plumes of warm moist air. Open-cells contain isolated LWP peaks surpassing 500 g m-2 collocated with strong updrafts, adjacent to glaciated cloud. Ni surpasses 10 L-1 at cloud temperatures < -15 °C. Precipitation shafts contain abundant large graupel (> 5 mm diameter) with liquid-equivalent precipitation intensities reaching 3 mm hr-1 developing cold pools with virtual potential temperature depressions reaching 1.3 K. Nonetheless, buoyancy fluxes of 200-250 W m-2 prevent sub-cloud decoupling. The updrafts supporting liquid water production occur at the upwind edge of the cold pools. This case expands the observations needed to better understand mixed-phase Arctic cloud processes.

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Publication Details

Journal
Atmospheric chemistry and physics
Published
2026-11-03
DOI
https://doi.org/10.5194/acp-26-15375-2026
Primary Topic
Atmospheric aerosols and clouds
Type
article
Field-Weighted Citation Impact
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article

A closed-to-open cell mixed-phase cloud transition observed over the Nordic Seas under high aerosol loading and strong surface fluxes

Jeffrey R. French, Sarah Woods, Athanasios Nenes, Tyler Tatro et al.
3 links
Atmospheric chemistry and physics
Atmospheric aerosols and clouds
article

A closed-to-open cell mixed-phase cloud transition observed over the Nordic Seas under high aerosol loading and strong surface fluxes

Jeffrey R. French, Sarah Woods, Athanasios Nenes, Tyler Tatro, Markus Dirk Petters, Bart Geerts, Varun Kumar, Paquita Zuidema, Jefferson R. Snider, Owen Cruikshank, Gunnar Noer, Zhien Wang, Romanos Foskinis, Henrik Skov, Ryan J. Patnaude, Sabine Eckhardt, Lise Lotte Sørensen, Elise Rosky, Silvia Henning, Greg M. McFarquhar, Teresa L Campos, Andreas Maßling, Russell Perkins, Coltin Grasmick, Kevin R. Barry, Florian Tornow, Nikolaos Evangeliou, Lu Zhang, Camille Mavis, Lintong Cai, Aaron R. Bansemer, Samuel Ephraim
article en

Abstract

Abstract. Closed-to-open cell mixed-phase cloud transitions within marine cold air outbreaks subjected to strong turbulent surface fluxes remain poorly understood despite their importance to high-latitude climate. The Cold-Air outbreak Experiment in the Sub-Arctic Region (CAESAR) research aircraft sampled closed-cells with cloud condensation nuclei concentrations surpassing 680 cm-3, decreasing to 90 cm-3 across a transition to open-cells. The aerosol likely originated from Siberian industrial emissions. With fetch, liquid water paths (LWPs) increase from 120 g m-2 to 270 g m-2 and cloud-top effective diameters increase from 10 μm to 16 μm, coincident with more riming. Ice particle number concentrations (Ni) are generally 2 L-1 or less, but exceed ice nucleating particle number concentrations by 100x. As the cloud-top inversion weakens and the boundary layer deepens further, ice precipitation co-exists with lidar-observed surface cold pools, modulated by entrainment events, juxtaposed with surface-based plumes of warm moist air. Open-cells contain isolated LWP peaks surpassing 500 g m-2 collocated with strong updrafts, adjacent to glaciated cloud. Ni surpasses 10 L-1 at cloud temperatures < -15 °C. Precipitation shafts contain abundant large graupel (> 5 mm diameter) with liquid-equivalent precipitation intensities reaching 3 mm hr-1 developing cold pools with virtual potential temperature depressions reaching 1.3 K. Nonetheless, buoyancy fluxes of 200-250 W m-2 prevent sub-cloud decoupling. The updrafts supporting liquid water production occur at the upwind edge of the cold pools. This case expands the observations needed to better understand mixed-phase Arctic cloud processes.

Atmospheric chemistry and physicsVol. 26(21)
University of California, Riverside (US), NSF National Center for Atmospheric Research (US), Goddard Institute for Space Studies (US), University of Wyoming (US), Norwegian Meteorological Institute (NO), University of Miami (US), National Technical University of Athens (GR), Aarhus University (DK), University of Michigan (US), Leibniz Institute for Tropospheric Research (DE), École Polytechnique Fédérale de Lausanne (CH), Stony Brook University (US), NILU (NO), Columbia University (US), University of Oklahoma (US), Colorado State University (US)
National Science Foundation, H2020 Excellent Science
Climate action
Openalex Percentile: Top 66%
Atmospheric aerosols and clouds
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