Abstract:Relationship between changes of (potential vorticity tendency, PVT) centroid positions in diffe-rent radii and the movement of Typhoon Megi was analyzed by numerical experiment, and the impact radius of PVT equation factors on PVT centroids positions was also discussed. The results show that within smaller radius, changes of the positive PVT centroid position are in accordance with Megi’s movement and are able to indicate the recurving of Megi. However, within larger radius, though the positive PVT centroid does not indicate the movement and turning of Megi directly, it reflects that the adjustment of atmospheric dynamical and thermal conditions in the corresponding area are favorable for Megi’s steering. PVT centroid movement is mainly affected by the horizontal advection, and is less affected by vertical advection and diabatic heating. The influences of vertical advection and diabatic heating related to thermal convection of Megi on PVT distribution are mainly concentrated near typhoon center. However, horizontal advection related to typhoon horizontal circulation can not only affect the PVT distribution within small radius, but also transport typhoon potential vorticity to farther area along northeast direction, which is the main reason for the difference of positive PVT centroid positions within different radii.