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Fog Modification with Giant Hygroscopic Nuclei

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  • 1 Cornell Aeronautical Laboratory, Inc., Buffalo, N.Y.
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Abstract

Analytic and experimental investigations were conducted to examine the concept of modifying fog with hygroscopic material. An approximate equation was derived that is useful in estimating the feasibility of such applied problems. The combined results show that it is possible to improve visibility in warm fog by seeding with micron-size salt particles (NaCl). The visibility in laboratory fog produced in a 600-m3 chamber was increased by factors of 3–10, with as little as 1.7 mg m−3 of NaCl being effective. Only a modest reduction (<1%) in ambient relative humidity by the giant salt particles is necessary to cause substantial evaporation of the fog droplets. Extrapolation of these results suggests that clearing a suitable landing zone for aircraft should not involve prohibitive amounts of properly sized seeding material.

Abstract

Analytic and experimental investigations were conducted to examine the concept of modifying fog with hygroscopic material. An approximate equation was derived that is useful in estimating the feasibility of such applied problems. The combined results show that it is possible to improve visibility in warm fog by seeding with micron-size salt particles (NaCl). The visibility in laboratory fog produced in a 600-m3 chamber was increased by factors of 3–10, with as little as 1.7 mg m−3 of NaCl being effective. Only a modest reduction (<1%) in ambient relative humidity by the giant salt particles is necessary to cause substantial evaporation of the fog droplets. Extrapolation of these results suggests that clearing a suitable landing zone for aircraft should not involve prohibitive amounts of properly sized seeding material.

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