Vertical Structure of the Sea Breeze Penetrating through a Large Urban Complex

A series of observations of the three-dimensional wind and thermal structure of the boundary layer was carried out during each summer season from 1986 to 1988 over the western portion of the Kanto plain. The data obtained during five selected days were analyzed, focusing on the sea breeze system which advances north-westward from Tokyo Bay through the Tokyo metropolitan area. A distinct sea breeze front was found on three of the days examined, whereas no front was observed during the remaining two days. The difference in the synoptic weather conditions between the frontal and non-frontal days was small, although a definite difference was found in the convective-scale thermal structure. Temporal and spatial interpolation methods followed by an adjustment using a variational analysis technique were applied to analyze the three-dimensional wind distribution. Trajectories of air parcels wore examined, based on the interpolated wind held. As a result, it was found that, for the frontal case, the upward motion at the leading edge of the sea breeze subsequently flowed upward over the stagnant region in the suburban are under the influence of the synoptic-scale onshore wind. This stagnant region persisted for a few hours, contributing greatly to the intensification of the front For the non-frontal days, upward flow was found over the urban area during the morning, but it readily diminished.