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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-758
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
06 Oct 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Comparing Airborne and Satellite Retrievals of Optical and Microphysical Properties of Cirrus and Deep Convective Clouds using a Radiance Ratio Technique
Trismono C. Krisna1, Manfred Wendisch1, André Ehrlich1, Evelyn Jäkel1, Frank Werner1,a, Ralf Weigel3,4, Stephan Borrmann3,4, Christoph Mahnke3, Ulrich Pöschl4, Meinrat O. Andreae4,6, Christiane Voigt2,3, and Luiz A. T. Machado5 1Leipziger Institut für Meteorologie (LIM), Universität Leipzig, Leipzig, Germany
2Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft und Raumfahrt (DLR), Oberpfaffenhofen, Germany
3Institut für Physik der Atmosphäre, Johannes Gutenberg-Universität Mainz, Mainz, Germany
4Biogeochemistry, Multiphase Chemistry, and Particle Chemistry Departments, Max Planck Institute for Chemistry (MPIC), Mainz, Germany
5Center of Weather Forecast and Climates Studies, National Institute for Space Research, Sao Jose Dos Campos, Brazil
6Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
anow at : Joint Center for Earth Systems Technology, University of Maryland, Baltimore, MD, USA
Abstract. Solar radiation reflected by cirrus and deep convective clouds (DCCs) was measured by the Spectral Modular Airborne Radiation Measurement System (SMART) installed on the German HALO (High Altitude and Long Range Research Aircraft) during the ML-CIRRUS and the ACRIDICON-CHUVA campaigns. In particular flights, HALO performed closely collocated measurements with overpasses of the Moderate Resolution Imaging Spectroradiometer (MODIS) on board of Aqua satellite. Based on the nadir upward radiance, the optical thickness τ and bulk particle effective radius reff of cirrus and DCC are retrieved using a radiance ratio algorithm which considers the cloud thermodynamic phase, the cloud vertical profile, multi layer clouds, and heterogeneity of the surface albedo. For the cirrus case, the comparison of τci and reff,ci retrieved on the basis of SMART and MODIS upward radiances yields a normalized mean absolute deviation of 0.5 % for τci and 2.5 % for reff,ci. While for the DCC case, the respective deviation is 5.9 % for τdcc and 13.2 % for reff,dcc. The larger deviations in case of DCC are mainly attributed to the fast cloud evolution and three-dimensional radiative effects. Measurements of spectral radiance at near-infrared wavelengths with different absorption by cloud particles are employed to investigate the vertical profile of cirrus effective radius. The retrieved values of cirrus effective radius are further compared with corresponding in situ measurements using a vertical weighting method. Compared to the MODIS observation, spectral measurements of SMART provide an increased amount of information on the vertical distribution of particle sizes at cloud top, and therefore allow to reconstruct the profile of effective radius at cloud top. The retrieved effective radius differs to in situ measurements with a normalized mean absolute deviation between 4–19 %, depending on the wavelength chosen in the retrieval algorithm. While, the MODIS cloud product underestimates the in situ measurements by 48 %. The presence of liquid water clouds below the cirrus, the variability of particle size distributions, and the simplification in the retrieval algorithm assuming vertically homogeneous cloud are identified as the potential error contributors.

Citation: Krisna, T. C., Wendisch, M., Ehrlich, A., Jäkel, E., Werner, F., Weigel, R., Borrmann, S., Mahnke, C., Pöschl, U., Andreae, M. O., Voigt, C., and Machado, L. A. T.: Comparing Airborne and Satellite Retrievals of Optical and Microphysical Properties of Cirrus and Deep Convective Clouds using a Radiance Ratio Technique, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-758, in review, 2017.
Trismono C. Krisna et al.
Trismono C. Krisna et al.
Trismono C. Krisna et al.

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Short summary
A validation of upward (cloud-reflected) radiance and MODIS cloud products was performed for the case of cirrus and DDC using airborne SMART measurements during two HALO campaigns, ML-CIRRUS and ACRIDICON-CHUVA. A vertical weighting method has been applied to allow a comparison between in situ and retrieved effective radius from remote sensing technique. Spectral measurements of SMART provide an increased amount of information on the vertical distribution of particle sizes at cloud top.
A validation of upward (cloud-reflected) radiance and MODIS cloud products was performed for the...
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