|MadSci Network: Earth Sciences|
Raindrops are not pure water. Most rain processes involve the accretion of moisture or cloud droplets on condensation nuclei. Some of the possible nuclei are called hygroscopic particles, particles that absorb cloud droplets and help them grow to raindrop size. Others may be dust, smoke, or any other number of aerosols. Salt particles are hygroscopic and have long been recognized as an important ingredient in the formation of raindrops. Salt concentrations have been measured in rain over marine areas but also far inland, wherever air masses have some history of interactions with a marine environment. Raindrops are often slightly salty over oceans and inland areas as well.
According to Duncan Blanchard, author of a lovely little book called From Raindrops to Volcanoes, Adventures With Sea Surface Meteorology, both the number and overall size of sea salt particles in marine air masses in hurricane winds increases dramatically as compared to light wind conditions in the same locations.
There is some research underway seeking to learn more about the role of
salt concentrations in rain and water vapor in hurricane formation. One
study at the University of Houston is investigating the amount of heat
transfered to a hurricane with the formation of sea spray and its
entrainment into the circulation. You can see the press release at:
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