A Simple Cloud Reflectance Model for Ship Tracks in Clouds
Abstract
Under certain meteorological conditions ships may generate 'tracks' in overlying marine stratus or stratocumulus clouds. These tracks are often not particularly evident to satellite sensors at visible wavelengths, but show up much more clearly at near infrared wavelengths, such as channel 3 (3.7 microns) of the Advanced Very High Resolution Radiometer (AVHRR) on NOAA polar-orbiting satellites. The phenomenon represents a potential naval intelligence technique, not only as a means to monitor and perhaps classify ships of other nations but also as a measure of environmental vulnerability of U.S. ships. A simple theoretical model was used as part of a ship track study to investigate effects of changes in microphysics and geometry on cloud reflectance at certain solar wavelengths. The model assumed a plane parallel homogeneous atmosphere of infinite extent and finite thickness, with Mie scattering and the delta-Eddington approximation for radiative transfer. The results were consistent with the theory that ship exhaust can increase the number density of smaller cloud droplets, which would lead to an increase in reflectance of incident solar radiation, especially at wavelengths near 3.7 microns.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1991
- Accession Number
- ADA247911
Entities
People
- Richard A. Siquig