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Apparent absorption of solar spectral irradiance in heterogeneous ice clouds

Schmidt, K. Sebastian and Pilewskie, Peter and Mayer, B. and Wendisch, Manfred and Kindel, Bruce and Platnick, Steven and King, Michael D. and Wind, Gala and Arnold, G. Tom and Heymsfield, Gerald and Tian, Lin and Kalesse, Heike (2010) Apparent absorption of solar spectral irradiance in heterogeneous ice clouds. Journal of Geophysical Research, 115 (D00J22), pp. 1-12. DOI: 10.1029/2009JD013124.

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Official URL: http://www.agu.org/journals/jd/jd1020/2009JD013124/2009JD013124.pdf


Coordinated flight legs of two aircraft above and below extended ice clouds played an important role in the Tropical Composition, Cloud and Climate Coupling Experiment (Costa Rica, 2007). The Solar Spectral Flux Radiometer measured up- and downward irradiance on the high-altitude (ER-2) and the low-altitude (DC-8) aircraft, which allowed deriving apparent absorption on a point-by-point basis along the flight track. Apparent absorption is the vertical divergence of irradiance, calculated from the difference of net flux at the top and bottom of a cloud. While this is the only practical method of deriving absorption from aircraft radiation measurements, it differs from true absorption when horizontal flux divergence is nonzero. Differences between true and apparent absorption are inevitable in any inhomogeneous atmosphere, especially clouds. We show, for the first time, the spectral shape of measured apparent absorption and compare with results from a three-dimensional radiative transfer model. The model cloud field is created from optical thickness and effective radius retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) Airborne Simulator and from reflectivity profiles from the Cloud Radar System, both on board the ER-2. Although the spectral shape is reproduced by the model calculations, the measured apparent absorption in the visible spectral range is higher than the model results along extended parts of the flight leg. This is possibly due to a net loss of photons into neighboring cirrus-free areas that are not contained within the model domain

Document Type:Article
Title:Apparent absorption of solar spectral irradiance in heterogeneous ice clouds
AuthorsInstitution or Email of Authors
Schmidt, K. SebastianUniv. of Colorado, Boulder, CO, USA
Pilewskie, PeterUniv. of Colorado, Boulder, CO, USA
Mayer, B.DLR / LMU
Wendisch, ManfredUniv. Leipzig
Kindel, BruceUniv. of Colorado, Boulder, CO, USA
Platnick, StevenNASA Goddard Space Flight Center, Greenbelt, MD, USA
King, Michael D.Univ. of Colorado, Boulder, CO, USA
Wind, GalaNASA Goddard Space Flight Center, Greenbelt, MD, USA
Arnold, G. TomNASA Goddard Space Flight Center, Greenbelt, MD, USA
Heymsfield, GeraldNASA Goddard Space Flight Center, Greenbelt, MD, USA
Tian, LinNASA Goddard Space Flight Center, Greenbelt, MD, USA
Kalesse, HeikeUniv. Mainz
Journal or Publication Title:Journal of Geophysical Research
Refereed publication:Yes
In Open Access:No
In ISI Web of Science:Yes
Page Range:pp. 1-12
Keywords:ice cloud absorption, 3-D radiative transfer, solar spectral measurements
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W EO - Erdbeobachtung
DLR - Research area:Space
DLR - Program:W EO - Erdbeobachtung
DLR - Research theme (Project):W - Vorhaben Atmosphären- und Klimaforschung (old)
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Atmospheric Remote Sensing
Deposited By: Jana Freund
Deposited On:28 Oct 2010 18:45
Last Modified:23 Jan 2014 11:36

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