Abstract
The Osaka Plain faces with the Hokusetsu and Rokko Mounts on the north. The purpose of the present study is to clarify flow structures of nocturnal drainages which break out on the south-facing slopes of the mounts and flow into the north part of the Osaka plain. Vertical profiles of horizontal wind velocity and turbulence properties on the ground are observed by the pilot balloon observation and a ultra-sonic anemometer. And such meteorological data as AMeDAS data were analyzed to examine horizontal flow extent. Vertical profiles of a north-south component of horizontal wind velocity of the nocturnal drainages are quite similar to those of gravity density currents which flow on inclined planes. The nocturnal dranages caused suddenly temperature drops when heads of the nocturnal drainages arrive at the observation point but doesn't contribute to suppress vertical turbulent temperature transport.
