Climatic features of the water vapor transport around east Asia and rainfall over Japan in June and September

The climatic features of the water vapor transport (WVT), which is closely related to rainfall in the middle latitudes around east Asia, are investigated using reanalysis data in June and September. A large amount of water vapor is intermittently transported in September in association with the movement of typhoons, but continuously transported in June. We defined a typhoon term as that when a typhoon or tropical storm is in Region A (20N–40N, 120E–150E) to estimate the effect on the poleward WVT. In September, the poleward WVT through Segment B (25N, 130E–150E) in the typhoon term (38.5% of the total term) was about 84% of that in the 20‐year‐accumulated total term, indicating that the climatic poleward WVT is greatly affected by typhoons and tropical storms. It is concluded that the contribution of typhoons and tropical storms is indispensable for the formation of a climatic atmospheric field around east Asia in September.