Abstract
The amount of precipitation is examined in relation to the upper wind field and temperature field in the pre-summer rainy season in Japan, June and July, for the years 1950 and 1951. It may be well explained as a result of vertical motions of baroclinic unstable waves in the westerlies. In the atmospheric structure during this season, there can be found a similarity to the structure of baroclinic unstable wave.
It is found from the data of 1946, 1950 and 1951 that the horizontal distribution of the mean zonal velocity also has some relations with the mechanism of precipitation, which suggests that a more complete, three-dimensional theory of baroclinic instability is needed.
Some brief remarkes are given on the relations between the basic flow and the disturbances.
