Diurnal Changes in Sea-Breeze Direction

Abstract

Simple mathematical theory suggests that the direction of the sea breeze must veer (move in an anticyclonic sense) during the day, until it is blowing parallel to the coast. Many observations of sea-breeze hodographs have shown that this rotation often does not occur and may sometimes be in the opposite (cyclonic) direction. Papers by Neumann and coworkers showed that either anticyclonic or cyclonic rotation could result from suitable combinations of Coriolis force and pressure gradient. Some observed examples of such cyclonic rotation are explained in the shift of direction from a ?local sea breeze? to a ?continental sea breeze? of a different direction; the strong pressure gradients associated with mountains can also produce cyclonic rotation. A study of the measured pressure gradient and wind velocities from southern England are shown to agree with the analysis of Neumann. It is concluded that topographical influences can often be responsible for cyclonic, rather than the expected anticyclonic, rotation.