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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 25 Oct 2019

Submitted as: research article | 25 Oct 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).

Small-scale structure of thermodynamic phase in Arctic mixed-phase clouds observed by airborne remote sensing during a cold air outbreak and a warm air advection event

Elena Ruiz-Donoso1, André Ehrlich1, Michael Schäfer1, Evelyn Jäkel1, Vera Schemann2, Susanne Crewell2, Mario Mech2, Birte Solveig Kulla2, Leif-Leonard Kliesch2, Roland Neuber3, and Manfred Wendisch1 Elena Ruiz-Donoso et al.
  • 1Leipzig Institute for Meteorology (LIM), University of Leipzig, Germany
  • 2Institute for Geophysics and Meteorology, University of Cologne, Germany
  • 3Alfred-Wegener-Institue Helmholtz Center for Polar and Marine Research (AWI), Germany

Abstract. The synergy between airborne lidar, radar, passive microwave, and passive imaging spectrometer measurements was used to characterize the vertical and small-scale (down to 10 m) horizontal distribution of the cloud thermodynamic phase. Two case studies of low-level Arctic clouds in a cold air outbreak and a warm air advection observed during the Arctic Cloud Observations Using airborne measurements during polar Day (ACLOUD) were investigated. Both clouds exhibited the typical vertical mixed-phase structure with mostly liquid water droplets at cloud top and ice crystals in lower layers. The cloud top horizontal small-scale variability observed during the cold air outbreak is dominated by the liquid water close to the cloud top and shows no indication of ice in lower cloud layers. Contrastingly, the cloud top variability of the case observed during a warm air advection showed some ice in areas of low reflectivity or cloud holes. Radiative transfer simulations considering homogeneous mixtures of liquid water droplets and ice crystals were able to reproduce the horizontal variability of this warm air advection. To account for more realistic vertical distributions of the thermodynamic phase, large eddy simulations (LES) were performed to reconstruct the observed cloud properties and were used as input for radiative transfer simulations. The simulations of the cloud observed during the cold air outbreak, with mostly liquid water at cloud top, realistically reproduced the observations. For the warm air advection case, the simulated cloud field underestimated the ice water content (IWC). Nevertheless, it revealed the presence of ice particles close to the cloud top and confirmed the observed horizontal variability of the cloud field. It is concluded that the cloud top small-scale horizontal variability reacts to changes in the vertical distribution of the cloud thermodynamic phase. Passive satellite-borne imaging spectrometer observations with pixel sizes larger than 100 m miss the small-scale cloud top structures, which limits their capabilities to provide indications about the cloud vertical structure.

Elena Ruiz-Donoso et al.
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Status: open (until 20 Dec 2019)
Status: open (until 20 Dec 2019)
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Elena Ruiz-Donoso et al.
Data sets

Spectral solar cloud top radiance measured by airborne spectral imaging during the ACLOUD campaign in 2017 E. Ruiz-Donoso, A. Ehrlich, M. Schäfer, E. Jäkel, and M. Wendisch

Aircraft measurements of spectral solar up- and downward irradiances in the Arctic during the ACLOUD campaign 2017 E. Jäkel, A. Ehrlich, M. Schäfer, and M. Wendisch

Airborne radar reflectivity and brightness temperature measurements with POLAR 5 during ACLOUD in May and June 2017 L.-L. Kliesch and M. Mech

Cloud top altitudes observed with airborne lidar during the ACLOUD campaign R. Neuber, L. V. Schmidt, C. Ritter, and M. Mech

Elena Ruiz-Donoso et al.
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Publications Copernicus
Short summary
Mixed-phase clouds, formed of water droplets and ice crystals, appear frequently in Arctic regions. Characterizing the distribution of liquid water and ice inside the cloud appropriately is important because it influences the cloud's impact on the surface temperature. In this study, we combined images of the cloud top with measurements inside the cloud to analyze in detail the 3D spatial distribution of liquid and ice in two mixed-phase clouds occurring under different meteorological scenarios.
Mixed-phase clouds, formed of water droplets and ice crystals, appear frequently in Arctic...