On mechanisms of rain-induced air-water gas exchange

David T. Ho, William E. Asher, Larry F. Bliven, Peter Schlosser, Elizabeth L. Gordan

Research output: Contribution to journalArticlepeer-review

59 Scopus citations

Abstract

Previous studies have shown that rain significantly enhances the rate of air-water gas exchange. However, even though an empirical correlation between the rain rate or kinetic energy flux (KEF) delivered to the water surface by rain and the gas transfer velocity has been established, the physical mechanisms underlying the gas exchange enhancement remain unexamined. During a series of experiments, the processes behind rain-induced air-water gas exchange were examined at NASA's Rain-Sea Interaction Facility (RSIF). Gas transfer velocities for helium (He), nitrous oxide (N2O), and sulfur hexafluoride (SF6) were determined for 22 rain rates (13.6 to 115.2 mm h-1) and three drop sizes (2.3, 2.8, 4.2 mm). Bubbles generated by the raindrops were characterized using a video-microscope technique, and surface waves were characterized by a capacitance probe. Additionally, rain-generated turbulence was inferred from friction velocities u*w calculated from KEF. Together, these data suggest that raininduced air-water gas exchange is mainly caused by turbulence-driven exchange processes, with bubbles contributing anywhere from 0 to 20%, depending on rain rate, drop size, and the solubility of the gas tracer. Furthermore, the data confirm that the previously selected variable KEF is the best correlate for rain-induced air-water gas exchange.

Original languageEnglish (US)
Article number1999JC000280
Pages (from-to)24045-24057
Number of pages13
JournalJournal of Geophysical Research: Oceans
Volume105
Issue numberC10
DOIs
StatePublished - Oct 15 2000
Externally publishedYes

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Atmospheric Science
  • Astronomy and Astrophysics
  • Oceanography

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