Diagnostic And Numerical Study Of The Influence Of Typhoon Danas (1324) On Typhoon Fitow (1323)

In recent years, some binary tropical cyclones cause serious damage to China, the interaction between the two typhoons has received more and more attention. Typhoon Fitow (1323) caused serious disasters to the East China region, while the typhoon Danas (1324) in the east. From the perspective of the interaction between the two typhoons, the characteristics and mechanism of Danas on Fitow is discussed by diagnostic analysis and numerical studies. The main results are as follows:1. Frist of all, by using CMA best track data and FNL data, the change of the relative position of the binary tropical cyclones and the environment water vapor transport in Fitow are diagnosed. It is found that Fitow around the landing running a counterclockwise circle, the intensity change of typhoon directly related to the variation of water vapor transport in the east boundary.2. The numerical simulation experiment is carried out by using the WRF model with removed the Danas. The results show that before Fitow landing, the water vapor channel is mainly caused by the environment field easterly stream on the southwest side of the subtropical high. Danas at the upstream intercepts environmental field delivering water vapor to Fitow and inhibited its development. However, after Fitow landing, Danas on the environment of the water vapor in turn plays a role in the transport, increasing the Fitow of the water vapor income, and increasing its north side of the strong precipitation. Danas, through water vapor as a link, affect the intensity of Fitow before its landing and Fitow’s asymmetric precipitation distribution onshore. In addition, Danas’s northward movement affects the intensity of subtropical high, causing the subtropical high’s east back, changing Fitow’s steer flow, affecting the Fitow landing position, and Fitow’s counterclockwise spinning around the landing by applying the southward steer flow.3. At last, the precipitation characteristics affected by Danas, Yuyao, which is far from far from the landing point and Ruian, which is on the north side of the Fitow landing point, are studied by using the Hysplit trajectory tracking model. The results show that both Yuyao and Ruian in Fitow before landing the precipitation water vapor mainly comes from the Fitow itself to the transportation environment easterly flow field. Ruian’s precipitation which occurred after Fitow landing, its water vapor supply mainly to the low altitude region water vapor above the ocean that attracted by Fitow’s cyclonic circulation. But Yuyao’s precipitation that occurred after landing, its water vapor comes from the high water vapor channel on the south side of the high water vapor channel, which transported by Danas. The water vapor transport of Danas plays an important role in the persistence of strong precipitation in Yuyao.The characteristics of environment water vapor channel, maintenance of intensity before landing, the track of typhoon around landing, the strong precipitation on the north side of Fitow are all affected by Danas. Such binary tropical cyclones with the horizontal distribution of the east and west, the influence of the latter on the strength, precipitation and track of the former should be fully considered in prediction.