Some Analytical Studies of the Heavy Rainfalls in Kyushu

Heavy rainfalls in Kyushu district which cause much damage have been often observed in the Baiu season. This paper describes the results of calculation and analysis of mainly the upper air divergence and vorticity, when we have heavy rainfalls in Kyushu. The results reveal the fact that the heavy rainfall takes place in the field of the low-level convergence and upper-level divergence of which absolute values are very large. And also there exists a strong positive vorticity in the lower layers, depending on the low-level jet stream. Interestingly it is found that the rainfall regions are seen to be divided according to the positive or negative sign of values of upper-level vorticity. Namely the center of the rainfall area is situated in southern Kyushu when positive vorticity prevails, and reversely in northern Kyushu when negative vorticity.