Multiple mechanisms generate a universal scaling with dissipation for the air‐water gas transfer velocity

• Published in: Geophysical research letters Vol. 44; no. 4; pp. 1892 - 1898
• Main Authors: Katul, Gabriel, Liu, Heping
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 28.02.2017; American Geophysical Union
• Subjects: Air-water exchanges; Air-water interface; air‐water exchange; Coastal zones; Dissipation; Eddies; Energy dissipation; Environmental conditions; ENVIRONMENTAL SCIENCES; gas transfer velocity; Gases; Geophysics; Interfaces; Kinematics; Kinetic energy; Kinetic energy dissipation; Kinetics; Kolmogorov scaling; Laboratory experiments; Marine environment; Mathematical models; Momentum transfer; Scaling; Scaling laws; Simplified surfaces; Structure-function relationships; surface divergence; surface renewal; Turbulence; Turbulent flow; Turbulent kinetic energy; Velocity; Viscosity; Water gas
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2016GL072256

A large corpus of field and laboratory experiments support the finding that the water side transfer velocity kL of sparingly soluble gases near air‐water interfaces scales as kL∼(νε)1/4, where ν is the kinematic water viscosity and ε is the mean turbulent kinetic energy dissipation rate. Originally predicted from surface renewal theory, this scaling appears to hold for marine and coastal systems and across many environmental conditions. It is shown that multiple approaches to representing the effects of turbulence on kL lead to this expression when the Kolmogorov microscale is assumed to be the most efficient transporting eddy near the interface. The approaches considered range from simplified surface renewal schemes with distinct models for renewal durations, scaling and dimensional considerations, and a new structure function approach derived using analogies between scalar and momentum transfer. The work offers a new perspective as to why the aforementioned 1/4 scaling is robust. Key Points Scaling laws empirically describing gas transfer velocity kL across marine and coastal systems are theoretically explained New theory predicts kL using Kolmogorov's universal structure function scaling laws for turbulence instead of surface renewal theory Work shows how multiple mechanisms with different assumptions subject to eddy turnover time constraint lead to similar scaling laws for kL