Note on surface wind stress over water at low and high wind speeds

In connection with recent work of predicting hurricane storm tides in New York Bay, it became desirable to adopt the most suitable value of surface wind stress over water at high wind velocities that current knowledge will sustain. To this end a review of available literature of field and laboratory experiments on the subject was undertaken and the collated results are presented. To some extent it has been found possible to resolve some of the wide disparities that have existed up to now between field and laboratory results by the quite simple expedient of adapting the laboratory data for wind speeds at 10-cm height (usually) to prototype conditions of wind speeds at 10-m height through use of the Karman-Prandtl equation for verticle velocity distribution. Some 47 authorities are quoted in arriving at Cd values of 0.0024±.0005 for strong winds and 0.0015±.0008 for light winds, in a wind stress relationship of the form τ0=CdρaU2 in which ρa is the mass density of the air and U the wind velocity at 10-m height. Although there is fairly satisfactory unanimity now regarding the Cd value for high winds, the situation is far less satisfactory for the case of light winds.