Observations of Flow Structures of Nocturnal Drainages in the Eastern Osaka Plain by Pilot Balloon Observations

Abstract

 Mountain winds are recognized to drop air temperatures at the foots of mountains in nighttime. If we try to use the winds as countermeasures for nocturnal heat-island phenomena, such informations as flow structures, occurrence mechanisms and etc. of the winds have to be obtained before that. The author indicated that cool air winds occur and drop air temperature by about 1 degree in the Eastern part of the Osaka Plain. The purpose of the present study is to clarify flow structures of the cool air winds by pilot balloon observations and meteolorogical data analyses. It is shown that the winds are mountain winds which are generated in surrounding mountains of the Osaka Plain and that layer thichnesses of the mountain winds are about 100m and maximum velocities of the winds are 2-3m/s.