An investigation into the potential effects of recurving western Pacific tropical cyclones on the large-scale circulation.

摘要

The objectives of this study were: (a) to document the East Asian subtropical jet acceleration and downstream cross-Pacific Rossby wave development that often occurs when tropical cyclones recurve in the western Pacific Ocean, and (b) to understand the dynamics of the observed acceleration and wave development and the potential role of tropical cyclone in forcing the jet acceleration and wave development. The objectives were achieved through composite and diagnostic analyses of selected meteorological parameters. Case studies were conducted of four storms included in the composites (Mirielle 1991; Gay 1992; Dale 1996; and Bart 1999).; When storms recurve in the western North Pacific the magnitude of the downstream jet acceleration ranges from a significant acceleration (e.g., >20 m s−1 increase in 24 h) to no acceleration. Rossby wave development ranges from large-amplitude wave development down through no development. The composite analyses and case studies suggest the large-scale flow structure is important in determining the magnitude of the observed downstream jet acceleration and wave development. This study has documented two distinct synoptic patterns. One pattern is associated with significant jet acceleration and downstream Rossby wave development. The other pattern is associated with storms that recurve with little interaction and impact on the large-scale flow pattern.; For recurving storms that occur with strong jet acceleration and wave development there is: (a) an interaction with a midlatitude baroclinic trough, (b) the development of a vigorous vertical circulation linking the circulations of the jet and the tropical cyclone, and (c) significant diabatic heating in the upper troposphere that contributes to the jet acceleration and downstream Rossby wave propagation.; For recurving storms that occur with weak jet acceleration and wave development there is: (a) a confluent jet-entrance region that lies over the recurvature region, and (b) an elongation of midlatitude baroclinic troughs in the zonal direction as they pass poleward of the recurving storms. The zonal elongation of the trough prevents strong interaction with the tropical cyclone.