Nonlinear interaction between rain- and wind-induced air-water gas exchange

• Published in: Journal of Geophysical Research: Oceans Vol. 117; no. C3
• Main Authors: Harrison, E. L., Veron, F., Ho, D. T., Reid, M. C., Orton, P., McGillis, W. R.
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 01.03.2012; American Geophysical Union
• Subjects: Atmospheric sciences; Earth sciences; Earth, ocean, space; Exact sciences and technology; Experiments; Gas exchange; Gases; Geophysics; Kinetic energy; Laboratories; Marine; Physical oceanography; Rain; Tropical environments; turbulence; Velocity; Wind; Wind speed; Delaware; United States; ANW, USA, Delaware; experimental studies; rainfall; kinetic energy; mass balance; atmospheric precipitation; tropical zone; energy transfer; Wind velocity; Wind effect; Wave property; air; ocean-atmosphere interaction; turbulence; North America; Rainfall rate; currents; parametrization; winds; Gas exchange
• ISSN: 0148-0227; 2169-9275; 2156-2202; 2169-9291
• DOI: 10.1029/2011JC007693

The combined effects of rain and wind on air‐water gas exchange were investigated with a series of experiments conducted at University of Delaware's Air‐Sea Interaction Laboratory (ASIL). During this study, the third ASIL Wind and Rain Experiment (WRX 3), a combination of three rain rates and eight wind speeds were executed using aqueous mass balances of SF6 to determine gas transfer velocities, k(600). In addition, measurements of wave properties, currents, and turbulence were obtained. Study results show that rain and wind effects combine nonlinearly to enhance air‐water gas exchange. Also, rainfall appears to contribute significantly to the total air‐water gas flux at low wind speeds, while at higher speeds rain effects appear to be negligible. We find that the range of conditions over which the rain effects are important is well defined by the ratio of rain kinetic energy flux to that of the wind. A nonlinear parameterization of k(600) for the combined effects of rain and wind is proposed. We extend this parameterization to field conditions and obtain the approximate rain rate and wind speed conditions where rain is expected to have a significant effect on air‐sea gas exchange. Low wind speed–high rain rate regions such as the tropics are regions where rain is expected to play a significant role. Key Points Rain and wind interact nonlinearly to enhance air‐sea gas exchange Rain effects are seen at lower wind speeds and disappear at higher speeds The limiting parameter is the ratio of the kinetic energy flux of rain to wind