摘要
In this study, the correlation between the frequency of summer tropical cyclones(TC) affecting areas around Korea over the last 37 years and the western North Pacifi c monsoon index(WNPMI) was analyzed. A clear positive correlation existed between the two variables, and this high positive correlation remained unchanged even when excluding El Ni?o-Southern Oscillation(ENSO) years. To investigate the causes of the positive correlation between these two variables, ENSO years were excluded, after which the 8 years with the highest WNPMI(strong WNPM phase) and the 8 years with the lowest WNPMI(weak WNPM phase) were selected, and the average difference between the two phases was analyzed.In the strong WNPM phase, TCs usually occurred in the eastern waters of the tropical and subtropical western North Pacifi c, and tended to pass the East China Sea on their way north toward Korea and Japan. In the weak WNPM phase, TCs usually occurred in the western waters of the tropical and subtropical western North Pacifi c, and tended to pass the South China Sea on their way west toward the southeastern Chinese coast and the Indochina peninsula. Therefore, TC intensity was higher in the strong WNPM phase, during which TCs are able to gain suffi cient energy from the sea while moving a long distance to areas nearby Korea. TCs also tended to occur more often in the strong WNPM phase.In the difference between the two phases regarding 850 h Pa and 500 h Pa streamline, anomalous cyclones were reinforced in the tropical and subtropical western North Pacifi c, while anomalous anticyclones were reinforced in mid-latitude East Asian areas. Due to these two anomalous pressure systems, anomalous southeasterlies developed in areas near Korea, with these anomalous southeasterlies playing the role of anomalous steering fl ows making the TCs head toward areas near Korea. Also, due to the anomalous cyclones developed in the tropical and subtropical western North Pacifi c, more TCs could occur in the strong WNPM phase.
In this study, the correlation between the frequency of summer tropical cyclones(TC) affecting areas around Korea over the last 37 years and the western North Pacifi c monsoon index(WNPMI) was analyzed. A clear positive correlation existed between the two variables, and this high positive correlation remained unchanged even when excluding El Ni?o-Southern Oscillation(ENSO) years. To investigate the causes of the positive correlation between these two variables, ENSO years were excluded, after which the 8 years with the highest WNPMI(strong WNPM phase) and the 8 years with the lowest WNPMI(weak WNPM phase) were selected, and the average difference between the two phases was analyzed.In the strong WNPM phase, TCs usually occurred in the eastern waters of the tropical and subtropical western North Pacifi c, and tended to pass the East China Sea on their way north toward Korea and Japan. In the weak WNPM phase, TCs usually occurred in the western waters of the tropical and subtropical western North Pacifi c, and tended to pass the South China Sea on their way west toward the southeastern Chinese coast and the Indochina peninsula. Therefore, TC intensity was higher in the strong WNPM phase, during which TCs are able to gain suffi cient energy from the sea while moving a long distance to areas nearby Korea. TCs also tended to occur more often in the strong WNPM phase.In the difference between the two phases regarding 850 h Pa and 500 h Pa streamline, anomalous cyclones were reinforced in the tropical and subtropical western North Pacifi c, while anomalous anticyclones were reinforced in mid-latitude East Asian areas. Due to these two anomalous pressure systems, anomalous southeasterlies developed in areas near Korea, with these anomalous southeasterlies playing the role of anomalous steering fl ows making the TCs head toward areas near Korea. Also, due to the anomalous cyclones developed in the tropical and subtropical western North Pacifi c, more TCs could occur in the strong WNPM phase.
基金
supported by the R&D Project of the Korea Meteorological Administration“Development and application of technology for weather forecast”(grant no.:NIMR-2013-B-1)
