A preliminary study on the relation between the thermal and geometric surface centroids of the Western Pacific Warm Pool

Numerous published results have shown the importance of the Western Pacific Warm Pool (WPWP) surface cen-troid movement in ENSO-(E1 Nino/Southern Oscillation) related studies. However, some recent research conclusions make it necessary to clarify the differences of the currently exiting two types of WPWP surface centroid: the geometric centroid and the thermal (heat) centroid. This study analyzes the physical backgrounds of the two types of centroid and points out their differences, which suggest that different types of centroid may serve different study purposes. This study also shows that the 'geometric center' of WPWP, actually a close approximation to the mass centroid, is more related to the Nino-3 region sea surface temperature (SST) anomaly and can also be regarded as an important indicator of ENSO events.