Transmission of Submillimeter Waves Through Water Clouds and Fogs

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  • 1 Division of Meteorological Physics, CSIRO, Aspendale, Australia
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Abstract

Some computations are made of submillimeter wave extinction in clouds and fogs using recent spectrometric results of the optical properties of water. At wavelengths > 1000μ an approximate formula is adequate in which extinction is proportional to cloud water content. At 2000 and 1000μ the extinction is 6.5 and 15.2 dB km−1 per gm m−3, respectively. Between 200 and 1000μ additional extinction occurs due to large droplets of diameters >20μ. Extinction for a typical fog distribution is computed and is found to be 41.1 dB km−1 per gm m−3 at 337 μ and 92.8 dB km−1 per gm m−3 at 200μ. Comparisons with experimental data at 1200 and 337μ shows qualitative agreement, but insufficient data on the composition of the clouds and fogs investigated precludes accurate comparison.

Abstract

Some computations are made of submillimeter wave extinction in clouds and fogs using recent spectrometric results of the optical properties of water. At wavelengths > 1000μ an approximate formula is adequate in which extinction is proportional to cloud water content. At 2000 and 1000μ the extinction is 6.5 and 15.2 dB km−1 per gm m−3, respectively. Between 200 and 1000μ additional extinction occurs due to large droplets of diameters >20μ. Extinction for a typical fog distribution is computed and is found to be 41.1 dB km−1 per gm m−3 at 337 μ and 92.8 dB km−1 per gm m−3 at 200μ. Comparisons with experimental data at 1200 and 337μ shows qualitative agreement, but insufficient data on the composition of the clouds and fogs investigated precludes accurate comparison.

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