16 Jan 2023
16 Jan 2023
Status: this preprint is currently under review for the journal ACP.

Vertical distribution of ice optical and microphysical properties in Arctic low-level mixed-phase clouds during ACLOUD

Emma Järvinen1, Franziska Nehlert1, Guanglang Xu1, Fritz Waitz1, Guillaume Mioche2, Regis Dupuy2, Olivier Jourdan2, and Martin Schnaiter1,3 Emma Järvinen et al.
  • 1Karlsruhe Institute of Technology, Karlsruhe, Germany
  • 2Laboratoire de Météorologie Physique (LaMP), Université Clermont Auvergne/OPGC/CNRS, Clermont Ferrand, France
  • 3schnaiTEC GmbH, Bruchsal, Germany

Abstract. Low-level (cloud tops below 2 km) mixed-phase clouds are important in amplifying warming in the Arctic region through positive feedback in cloud fraction, water content and phase. In order to understand the cloud feedbacks in the Arctic region, good knowledge of the vertical distribution of the cloud water content, particle size and phase is required. Here we present seven in-situ vertical profiles of cloud microphysical and optical properties measured in the European Arctic during the ACLOUD campaign. Late spring- and summer-time stratiform clouds were sampled over pack ice, marginal sea ice zone and open ocean surface with cloud top temperatures varying between −15 and −1.5 °C. The results show that, although liquid phase dominates the upper parts of the clouds, ice phase was frequently observed in the lower parts down to cloud top temperatures as warm as −3.8 °C. In the studied vertical cloud profiles the average liquid phase microphysical properties, droplet number concentration, effective radius and liquid water content, varied between 22 and 120 cm−3, 16 and 27 μm, 0.09 and 0.48 gm−3, respectively. The average ice phase microphysical properties, ice number concentration, effective radius and ice water content, varied between 0.01 and 35 L−1, 24 and 75 μm, 0.003 and 0.08 gm−3, respectively. The elevated ice crystal number concentrations and ice water paths observed for clouds with cloud top temperatures between −3.8 and −8.7 °C can be likely attributed to secondary ice production through rime-splintering. Low asymmetry parameters between 0.69 and 0.76 were measured for the mixed-phase ice crystals with a mean asymmetry parameter of 0.72. The effect of the ice phase for radiative transfer was investigated for the four cloud cases potentially affected by secondary ice production. Generally the ice phase has only a minor effect to the cloud transmissivity and albedo, except in a case where ice phase dominated the upper cloud layer extinction. In this case cloud albedo was increased by 10 %. The presented results highlight the importance of accurate vertical information of cloud phase for radiative transfer and provide a suitable data set for testing microphysical parameterisations in models.

Emma Järvinen et al.

Status: open (until 01 Mar 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Emma Järvinen et al.

Data sets

SID-3 analysis results for 2D scattering patterns during the ACLOUD campaign in 2017 Schnaiter, M. and Järvinen, E.

PHIPS particle-by-particle data for the ACLOUD campaign in 2017 Schnaiter, M. and Järvinen, E.

Airborne in-situ measurements of the aerosol absorption coefficient, aerosol particle number concentration and size distribution of cloud particle residuals and ambient aerosol particles during the ACLOUD campaign in May and June 2017 Mertes, S. and Kästner, U. M. A.

1 Hz resolution aircraft measurements of wind and temperature during the ACLOUD campaign in 2017 Hartmann, J., Lüpkes, C., and Chechin, D.

CDP, CIP and PIP In-situ arctic cloud microphysical properties observed during ACLOUD-AC3 campaign in June 2017 Dupuy, R., Jourdan, O., Mioche, G., Gourbeyre, C., Leroy, D., and Schwarzenböck, A.

Emma Järvinen et al.


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Short summary
Arctic is warming faster than other regions. Arctic low-level mixed-phase clouds, where ice crystals and liquid droplets co-exist, are thought to have an important role in the Arctic warming. Here we show airborne measurements of vertical distribution of liquid and ice particles and their relative abundance. Ice particles are found in relative warm clouds. When the ice particles are located at the top of the cloud they have an important role in redistributing incoming sun light.