Abstract:Typhoons Ramasun and Kalmaegi along west route influenced Yunnan in 2014, where rainstorm distribution characteristics and the relative position of tropical cyclone had significant differences. The diagnosis results indicate that production of rainstorm distribution difference was mainly caused by the role of ambient flow field, which caused frontogenesis, then energy change, together with the effect of topo graphy. Particularly, low level westerly (easterly) jet and convergence at south (north) side of Ramasun Typhoon center enhanced, causing generation of heavy rainfall. However, because water vapor content in lower layer of south side was higher than that of north side, the southwest Yunnan edge and Red River Valley windward slope had uplift effect, the rainfall amplified. Precipitation of south side was heavier than that of north side. In addition, thermodynamic properties differences of flow between south and north side caused frontogenesis. Frontal zone at low level enhanced, beneficial to the development of severe precipitation on the northeastern side of Ramasun, southeast Yunnan. Furthermore, intersection of the easterly and westerly made divergence enhancing, then baroclinic available potential energy was released, which caused divergent wind kinetic energy to increase, and increase of divergent wind kinetic energy was relative to the change of precipitation peak caused by Ramasun. However, as Kalmaegi was influencing Yunnan, the center position of tropical cyclone and Bay of Bengal low pressure were both further south, and the southwest monsoon was also further south. The low level jet at Kalmaegi northeastern side was the main factor influencing rainfall over Yunnan, and the intensity of low level jet and zonal convergence at the jet front left quadrant were both stronger than that by Ramasun, so the precipitation of Kalmaegi northeastern side was more intense than that of Ramasun. In addition, the uplift effect of terrain played an important role in the generation of heavy rainstorm at south Yunnan edge. Moreover, frontal zone at low level enhanced, which was also beneficial to the development of severe precipitation over northeast Yunnan at the northeastern side of Kalmaegi. Furthermore, increasing rotational wind kinetic energy was relative to precipitation peak, and the formation of the first precipitation peak in the edom of central Yunnan was related to baroclinic processes. However, at the second precipitation peak, south jet was strengthened on the east side of depression inverted trough, and rotational velocity field transported kinetic energy to heavy rain area, then kinetic energy over heavy rain area increased significantly, which was related to barotropic processes.