NUMERICAL SIMULATION OF COLD NOCTURNAL DRAINAGE FLOWS IN THE NORTHERN PART OF OSAKA PLAIN

Abstract

 The authors showed that cold nocturnal darainage flows break out in the northern part of Osaka Plain, can lower temperature of the part by 2℃ and have velocity profiles similar to those of gravity density currents on inclined plains. In the present study, numerical simulation using the WRF was conducted to examine structures and generation mechanisms of the flows. The accuracy of the calculation was checked by comparison with some existing meteorological data. The simulation results showed that the drainage flow which the authors have been studying is generated by outflow of cold air mass which accumulates in the Tada basin into Osaka Plain and there are other nocturnal drainages which flow on flood plains of the Akutagawa and Aigawa Rivers in the part.