Further Study of Typhoon Tracks and the Low-Frequency(30-60 Days)Wind-Field Pattern at 850 hPa

摘要

The association of typhoon tracks over the western Pacific with the low-frequency wind-field pattern of atmospheric intraseasonal (30-60 days) oscillation at 850 hPa is further studied by using observational data analyses. Comparative analyses of the composite wind fields at 850 hPa, contrasting the atmospheric intraseasonal oscillation (ISO) with the original circulation, show that the typhoon tracks are closely related to the wind pattern of the ISO but are not obviously related to the original wind fields. Case studies of two typhoons in 2006 also show that the low-frequency wind-field pattern, particularly the maximum-value line (belt) of low-frequency cyclonic vorticity at 850 hPa, is closely related to the typhoon track. Therefore, the lowfrequency circulation pattern and the maximum-value line (belt) of low- frequency cyclonic vorticity at 850hPa can be used to predict typhoon tracks over the northwestern Pacific.