The Role of Background Cloud Microphysics in the Radiative Formation of Ship Tracks

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Author
Platnick, S.
Durkee, P.A.
Nielsen, K.
Taylor, J.P.
Tsay, S.-C.
King, M.D.
Ferek, R.J.
Hobbs, P.V.
Rottman, J.W.
Date
2000-08-15Metadata
Show full item recordAbstract
The authors investigate the extent to which the contrast brightness of ship tracks, that is, the relative change
in observed solar reflectance, in visible and near-infrared imagery can be explained by the microphysics of the
background cloud in which they form. The sensitivity of visible and near-infrared wavelengths for detecting
reflectance changes in ship tracks is discussed, including the use of a modified cloud susceptibility parameter,
termed the ‘‘contrast susceptibility,’’ for assessing the sensitivity of background cloud microphysics on potential
track development. It is shown that the relative change in cloud reflectance for ship tracks is expected to be
larger in the near-infrared than in the visible and that 3.7-mm channels, widely known to be useful for detecting
tracks, have the greatest sensitivity. The usefulness of contrast susceptibility as a predictor of ship track contrast
is tested with airborne and satellite remote sensing retrievals of background cloud parameters and track contrast.
Retrievals are made with the high spatial resolution Moderate Resolution Imaging Spectroradiometer Airborne
Simulator flown on the National Aeronautics and Space Administration’s high-altitude ER-2 aircraft, and with
the larger-scale perspective of the advanced very high resolution radiometer. Observed modifications in cloud
droplet effective radius, optical thickness, liquid water path, contrast susceptibility, and reflectance contrast are
presented for several ship tracks formed in background clouds with both small and large droplet sizes. The
remote sensing results are augmented with in situ measurements of cloud microphysics that provide data at the
smaller spatial scales.
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This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.Collections
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