Atmospheric Transmissivity Update - 1988
COAST GUARD WASHINGTON DC OFFICE OF RESEARCH AND DEVELOPMENT
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The Coast Guard uses atmospheric visibility data collected in 1958 and 1959 when calculating the effective luminous range of aids to navigation. Presently, Coast Guard aid designers question whether or not increases in population and industry have changed atmospheric visibility along our coasts. Recent atmospheric visibility data in the form of transmissivity curves are presented to answer this question. National Weather Service NWS visibility records from the maritime zone form the basis for our study. Data from these records were sorted into 28 geographical zones. Curves were fit to frequency distributions within each zone, forming new atmospheric transmissivity curves, one for each zone. The new and old transmissivity curves differ considerably in many regions. The old transmissivity curves should not be used to estimate atmospheric conditions. Further study has shown that even the new transmissivity curves can be improved. Accurate, localized curves can be obtained by decreasing the area size to the limit that the NWS data will allow. It is recommend that the Coast Guard accept small, localized regions for calculating transmissivity curves. In addition, software needs to be developed which uses new localized curves and the aid design tables and calculations. This product would remove the need for the look up tables and tedious computations presently used during aid design. Keywords Transmissivity Aids to navigation Allards law Luminous range Visibility.
- Atmospheric Physics