Contribution of free tropospheric aerosols to  Arctic low-level cloud droplets formation  and longwave radiative forcing

Pohorsky, Roman; Guy, Heather; Brooks, Ian Morley; Haberstock, Lea; Fauré, Nicolas; Zieger, Paul; Kojoj, Julia; Murto, Sonja; Calmer, Radiance; Heutte, Benjamin; Lonardi, Michael; Thomson, Erik Schurch; Tjernström, Michael; Creamean, Jessie; Nenes, Athanasios; Schmale, Julia

doi:10.5194/acp-26-10331-2026

Articles | Volume 26, issue 14

https://doi.org/10.5194/acp-26-10331-2026

© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-26-10331-2026

© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 26, issue 14

Research article

|

24 Jul 2026

Research article |

| 24 Jul 2026

Contribution of free tropospheric aerosols to Arctic low-level cloud droplets formation and longwave radiative forcing

Roman Pohorsky, Heather Guy, Ian Morley Brooks, Lea Haberstock, Nicolas Fauré, Paul Zieger, Julia Kojoj, Sonja Murto, Radiance Calmer, Benjamin Heutte, Michael Lonardi, Erik Schurch Thomson, Michael Tjernström, Jessie Creamean, Athanasios Nenes, and Julia Schmale

Supplement

https://doi.org/10.5194/acp-26-10331-2026-supplement

Data sets

Vertical in situ measurements of aerosols and meteorological variables from expedition ARTofMELT, Arctic Ocean, 2023, Dataset version 1 Roman Pohorsky et al. https://doi.org/10.17043/oden-artofmelt-2023-aerosols-vertical-1

A comprehensive characterisation of natural aerosol source samples from expedition ARTofMELT, Arctic Ocean, 2023, Dataset version 1 Julia Kojoj et al. https://doi.org/10.17043/oden-artofmelt-2023-aerosol-source-samples-1

Radiosonde profiles from expedition ARTofMELT, Arctic Ocean, 2023, Dataset version 1 Sonja Murto et al. https://doi.org/10.17043/oden-artofmelt-2023-radiosonde-1

Cloud radar data from expedition ARTofMELT, Arctic Ocean, 2023, Dataset version 1 Heather Guy et al. https://doi.org/10.17043/oden-artofmelt-2023-cloud-radar-1

Cloud base heights and atmospheric backscatter observations from expedition ARTofMELT, Arctic Ocean, 2023 - cloudnetpy input, Dataset version 1 Heather Guy et al. https://doi.org/10.17043/oden-artofmelt-2023-ceilometer-cloudnetpy-1

HALO lidar vertical stare data from expedition ARTofMELT, Arctic Ocean, 2023, Dataset version 1 Ian Brooks and Heather Guy https://doi.org/10.17043/oden-artofmelt-2023-halo-lidar-1

Ice station surface meteorology and radiation data from expedition ARTofMELT, Arctic Ocean, 2023, Dataset version 1 Heather Guy et al. https://doi.org/10.17043/oden-artofmelt-2023-surface-meteorology-ice-station-1

Wind, temperature, relative humidity, surface temperature and radiation from expedition ARTofMELT, Arctic Ocean, 2023, Dataset version 1 Sonja Murto et al. https://doi.org/10.17043/oden-artofmelt-2023-weather-station-1

Backward trajectories within a circle around the ship using the LAGRANTO model, for the expedition ARTofMELT, Arctic Ocean, 2023, Dataset version 1 Sonja Murto and Michael Tjernström https://doi.org/10.17043/oden-artofmelt-2023-trajectories-backward-circle-1

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Short summary

This study presents tethered-balloon observations above Arctic sea ice showing that enhanced aerosol concentrations above low-level clouds are commonly observed. A closure analysis demonstrates that entrainment of these aerosols is required to reproduce observed cloud droplet numbers. Simulations indicate that neglecting this source can bias longwave radiative forcing, highlighting the need for vertical aerosol observations and improved model representation of aerosol entrainment at cloud top.