Salt Particles and Raindrops in Hawaii

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  • 1 Hawaii Institute of Geophysics, University of Hawaii, Honolulu
  • | 2 Graduate School of Oceanography, University of Rhode Island, Kingston
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Abstract

Particles of sea salt of different size in the marine air of Hawaii exhibit different ratios of iodine to chlorine, whereas raindrops of various sizes in Hawaii warm orographic showers contain iodine and chlorine in a relatively constant ratio. The mean value of the I/Cl ratio for raindrops (∼2.0 × 10−3) corresponds to the mean found among the smaller of the salt particles of weight range ∼10−12–10−14 gm. On the other hand, the mean I/Cl value among the giant salt particles of weight range of ∼10−8–10−12 gm is shown to be ∼3 × 10−4. It appears that raindrop growth occurs through coalescence among cloud droplets formed on the 10−12–10−14 gm salt particles. This result is interpreted to mean that in warm oceanic tradewind clouds giant salt nuclei may not, after all, be essential to the formation of raindrops.

Abstract

Particles of sea salt of different size in the marine air of Hawaii exhibit different ratios of iodine to chlorine, whereas raindrops of various sizes in Hawaii warm orographic showers contain iodine and chlorine in a relatively constant ratio. The mean value of the I/Cl ratio for raindrops (∼2.0 × 10−3) corresponds to the mean found among the smaller of the salt particles of weight range ∼10−12–10−14 gm. On the other hand, the mean I/Cl value among the giant salt particles of weight range of ∼10−8–10−12 gm is shown to be ∼3 × 10−4. It appears that raindrop growth occurs through coalescence among cloud droplets formed on the 10−12–10−14 gm salt particles. This result is interpreted to mean that in warm oceanic tradewind clouds giant salt nuclei may not, after all, be essential to the formation of raindrops.

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