Abstract
Based on six-hourly precipitation and upper-air observations over the Kyushu Islandfor ten years pre-summer rainy seasons (Baiu) from 1962 to 1971, statistical relationships are studied on the amount of precipitation and the tropospheric wind speed.
It is clearly shown that the amount of precipitation is highly correlated with the lower tropospheric wind speed and higher correlation coefficient is obtained for later wind speed, which supports the hypothesis that the momentum in the lower troposphere is increased as a result of convective activity. In cases of heavy precipitation, unbalanced low-level jets are most likely to appear and the maximum frequency of wind speed is observed around 18m/sec throughout the troposphere.
