Relationship Between the Change in Size of Tropical Cyclones and Spatial Patterns of Precipitation

The relationship between the size change of tropical cyclones (TCs) and radial distribution of precipitation was investigated for TCs occuring over the western North Pacific Ocean with satellite observation data. The size of a TC is defined as the radial extent of 15 m s(-1) winds (R15). The spatial distribution of precipitation was investigated by extracting two subperiods, which are the size-increasing period and the size-stationary period, as determined from R15 evolution. The results show a contrast that during the size-increasing period, precipitation falls both inside and outside the R15, whereas during the size-stationary period, it is concentrated near the center of the TC and falls less around and outside R15. This contrast is also confirmed statistically by composite analysis using 64 TC cases. Further analysis reveals that this contrast does not depend on the intensity or the change in intensity of the TC, which indicates that the area of precipitation related to the intensity or intensity change of TCs is different from that related to the size change of TCs. Finally, we examined the radial distribution of inertial stability in TCs and found that precipitation during the size-stationary period occurs in a region with a higher inertial stability than that which occurs during the size-increasing period.