An observational study of land and sea breezes in the southern part of the Osaka district

Detailed observations of the wind and temperature profiles in land and sea breeze situations were made in the southern part of the Osaka district by using pilot-balloon with double-theodolite method and lower-troposphere-radiosonde in the summer from 1981 to 1983. Diurnal course of the wind system observed is as follows. In the morning and early afternoon, an onshore flow from Osaka Bay is observed within several hundred meters height above the ground surface. The depth of the flow tends to thicken with elapse of time. In the late afternoon and evening, a flow parallel to the coastline and blowing from the Kii channel prevails in the first thousand meters layer of the atmosphere, which shows, in the middle of the period, the characteristics of the nocturnal low-level jet. After midnight until dawn, a flow having the reverse direction to the former appears in a few hundred meters layer of the atmosphere. A flow pertinent to the land/mountain breeze in the area under study appears only in the lowest several tens of meters layer of the atmosphere. A decrease in wind speed by a few meters a second and a veering in wind direction by about 10 degrees are seen in the first few hundred meters layer of the atmosphere between coast and several kilometers inland in the sea breeze situation, suggesting modification of the sea breeze during travel over land. Diurnal change of the temperature field below 3000 meters height above the ground surface observed by serial ascents of lower-troposphere-radiosondes is also discussed. (author)