THE HUMIDITY GRADIENT OVER THE SEA SURFACE

Abstract

Abstract Observations of humidity and temperature at three levels above the sea surface are discussed, using new data obtained by Lt. F. L. Black, U.S.N., in 1937 at wind velocities up to 16.5 m sec−1. It is shown that these and earlier data indicate that the transfer of water vapor and momentum obey similar laws and that the sea surface at wind velocities below 5 m sec−1 behaves as a hydrodynamicalIy smooth surface and at velocities above 7 m sec−1 as a hydrodynamically rough surface with roughness length 0.6 cm. The observations indicate a great variability in the humidity gradient between heights of 6 m and 30 m and a relatively small variability in the difference between the vapor pressures at the sea surface and at 6 m.