It was shown that heavy rainfall induced by interaction of cold air with TC circulation was seen in both TC cases after TC moving toward north. However, there were obvious differences in precipitation distribution features induced by cold air in these two TCs: Matmo showing more meridional fashion with northeast-southwest rainfall belt along the TC inverted trough; while the precipitation feature of Soudelor appearing a zonally shape with a west-east distribution along the east-wind low-level jet on north of the TC circulation.
The trajectories of air parcels motion of cold air in each TC were analyzed through Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) of NOAA Air Resources Laboratory (ARL) in this paper to investigate the intrusion path of cold air. It is shown that the clod air interacted with TC outer-region circulation through a northwest path in Matmo with the cold air of middle layer troposphere including both cold air induced by northwest region clod trough moving eastward and cold air from Northeast China. Contradistinctively, the intrusion route of cold air in Soudelor was east path, and the cold air source of Soudelor was only from the cold trough system locating at Northeast China. As a result, the intensity of cold air in Soudelor was weaker than Matmo. In vertical direction, low-level cold air intrusion was prior to middle level in Matmo, while that for Soudelor was just on the contrary. The different vertical structure and intensity of cold air may result in different interaction forms between cold air and TC circulation.
Caused by the different interaction forms of cold air with TC circulation between these two TCs, the precipitation features of them were different too. There was distinct low-level TC inverted trough north of the circulation of Matmo with very strong cold- and warm- temperature advection and distinct surface frontogenesis in Matmo. And favorable conditions for heavy precipitation such as the positive-vorticity, upward motion are located along the TC inverted trough with a northeast-southwest distribution.
As for Soudelor, TC inverted trough was not found in the TC circulation, and the low-level cold-advection and surface frontogenesis in it were both weaker than that of Matmo. Significant positive vorticity and upward motion were triggered by low-level east wind jet northern of TC circulation. Furthermore, the intensification of potential instability in the north side of Soudelor caused by middle level cold air intrusion finally resulted in the heavy rainfall which performed an east-west distribution to the north of TC.