This study investigates the exchange of momentum between the atmosphere and ocean using data collected from four oceanic field experiments. Direct covariance estimates of momentum fluxes were collected in all four experiments and wind profiles were collected during three of them. The objective of the investigation is to improve parameterizations of the surface roughness and drag coefficient used to estimate the surface stress from bulk formulas. Specifically, the Coupled Ocean-Atmosphere Response Experiment (COARE) 3.0 bulk flux algorithm is refined to create COARE 3.5. Oversea measurements of dimensionless shear are used to investigate the stability function under stable and convective conditions. The behavior of surface roughness is then investigated over a wider range of wind speeds (up to 25 m s 21 ) and wave conditions than have been available from previous oversea field studies. The wind speed dependence of the Charnock coefficient a in the COARE algorithm is modified to a 5 mU 10N 1 b, where m 5 0.017 m 21 s and b 5 20.005. When combined with a parameterization for smooth flow, this formulation gives better agreement with the stress estimates from all of the field programs at all winds speeds with significant improvement for wind speeds over 13 m s 21. Wave age-and wave slope-dependent parameterizations of the surface roughness are also investigated, but the COARE 3.5 wind speed-dependent formulation matches the observations well without any wave information. The available data provide a simple reason for why wind speed-, wave age-, and wave slopedependent formulations give similar results-the inverse wave age varies nearly linearly with wind speed in long-fetch conditions for wind speeds up to 25 m s 21.

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There are two instances of an error in Edson et al. (2013). In both the abstract (p. 1589), and in section 2c (first line on p. 1598), the value for m is incorrect. In both cases, the value should be m 5 0.0017, and not m 5 0.017 as originally appeared.The authors regret any inconvenience this error may have caused.

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A year‐long mooring data are used to study the upper ocean unstable events and instabilities at 18°N 89°E, which is a climatologically important region in the North Bay of Bengal. Near‐surface stability is studied from the context of the buoyancy frequency normalized shear (Vz/N) and reduced shear (S2−4N2) which are convenient measures to quantify flow stability, compared to the more widely used Richardson number (Ri). The analysis is carried out across three contrasting time periods, the monsoon, postmonsoon, and the winter of year 2012. Although it is well known that the flow stability changes from stable to unstable at Ri = Ricr=0.25, the relative importance of the perturbations of shear and buoyancy frequency in driving the unstable events is not well studied over the open oceans and more particularly over the Bay of Bengal. At 18°N, 89°E both higher than average shear and lower than average buoyancy frequency perturbations are crucial in driving the unstable events during the summer and premonsoon period. However, at increasing depths, the influence of shear perturbations becomes more dominant. Invoking the Miles‐Howard criteria for flow instability, it is seen that during the postmonsoon period, the buoyancy frequency perturbations are more critical than shear perturbations in driving the unstable events. In winter, the unstable events are influenced by both the buoyancy frequency and shear perturbations.