NOTES AND CORRESPONDECEScaling Reasoning and Field Data on the Sea Surface Roughness Lengths for Scalars

Abstract

The heat and mass transfer over the sea is considered in terms of the sea surface roughness lengths for scalars, z 0T for potential temperature u, and z 0q for specific humidity q, or alternatively, in terms of the roughness-layer scalar increments, du and dq. A new scaling reasoning is proposed in support of the familiar square root dependence of the above increments on the roughness Reynolds number, Re0u 5 z 0uu * /n, where z 0u is the sea surface aerodynamic roughness length, u * is the friction velocity, and n is the molecular viscosity of the air. Scaling predictions are validated using data from measurements made by the National Oceanic and Atmospheric Administration’s Environmental Technology Laboratory aboard the R/V Moana Wave in the Tropical Ocean Global Atmosphere Coupled Ocean‐Atmosphere Response Experiment in 1992‐93 and the R/PFLIP in the San Clemente Ocean Probing Experiment in September 1993. Data presented as the dimensionless scalar increments (or the ratios z 0u/z 0T and z 0u/z 0q) versus Re 0u show a good agreement with theoretical predictions, especially at Re0u . 2 (over stormy sea). The resulting roughness-length formulations are recommended for practical use in climate and mesoscale air‐sea interaction models.