The Effects Of Tropical Atmospheric Quasi-Biweekly Oscillation On Typhoon Tracks Over Western North Pacific

By using the Tropical cyclones(TCs) data from the American joint typhoon woring center (JTWC),reanalysis wind and height data by NCEP/NCAR, this paper discusses the modulation of typhoon tracks over the Western North Pacific by the atmospheric quasi-biweekly oscillation(QBWO) in the summer (June through october) for the nearly32years. In addition,by using of the wind data, This paper discusses the modulation of Quasi-biweekly oscillation of cross-equatorial flow on typhoon tracks over the Western North Pacific by using the Tropical cyclones (TCs) data and the wind data. We divide the typhoon tracks into seven types:straight west-moving typhoons, northwest-moving typhoons, typhoons recurving and landing in China, typhoons recurving to the regions between China and Japan, typhoons recurving and landing in Japan, typhoons recurving to the east of Japan and typhoons east of140°E. By the methods of band-pass filtering and the methods of lead and lag regression, this paper ananlyzes the original circulation, low-frequency circulation and the evolution of low-frequency circulation in the period of the atmospheric QBWO and the evolution of Low-frequency circulation of the cross-equatorial flow in925hPa. By analyzing the impact on the typhoons over the Western North Pacific of atmospheric quasi-biweekly oscillation, we find that the atmospheric have the characteristics of QBWO. The atmospheric QBWO influences the intensity and position of monsoon trough and subtropical high by the low-frequency cyclone and low-frequency anticyclone,thus influencing the formed location and movement of typhoon tracks. The low-frequency cyclone east of the Philippines will conducive to the formation of typhoons.The zone of positive vorticity of low-frequency cyclone will affect the movement of typhoon. In addition, the atmospheric QBWO eastward propagation in the subtropics also influences the typhoon tracks. The interaction of tropical and subtropical QBWO performs an important function on the typhoon tracks. Additionally, by analyzing the impact on the typhoons of the quasi-biweekly oscillation of cross-equatorial flow in925hPa, we find that the radial wind and cross-equatorial flow in925hPa have the characteristics of periodic oscillations of10to20days. In the equatorial region of Western North Pacific, the low-frequency cross-equatorial flow and radial wind provide advantageous conditions of energy and water vapor transport of Northern and Southern Hemisphere. The low-frequency cross-equatorial flow can influences the low-frequency cyclone and anticyclone and modulate the typhoon tracks by regulating the position and strength of ITCZ and subtropical high.