Role of the 1020-day Oscillation in Rainstorms in October 2010 over Hainan, China
The eastward propagation of the 1020-day oscillation in the tropical Indian Ocean is similar to the convectively coupled Kelvin-Rossby wave. In addition, the westward propagation of the 1020-day oscillation from the western Pacific is roughly similar to the equatorial Rossby wave in both its periodicity and propagation speed. Thus, the coupled Kelvin-Rossby wave and equatorial Rossby wave may have worked together to induce the rainstorms over Hainan in October 2010. We also investigated the propagation of the 3060-day oscillation, and the results showed that there is neither eastward propagation from the Indian Ocean nor westward propagation from the western Pacific on the 3060-day time scale.
We also examined SST anomalies in September and October 2010. The spatial distribution of the SST anomaly shows a La Niña pattern. The positive SST anomalies exist almost throughout the tropical Indian Ocean and western Pacific, forcing the active convection center and favoring the corresponding propagation from the Indian Ocean to the maritime continent. Meanwhile, during the La Niña event, the westward shift of the suppressed convection and easterly anomalies over western-central Pacific prevented the 10-20-day oscillation from penetrating farther eastward, and consequently it stayed at the maritime continent longitudes.