Is there a linkage between the tropical cyclone activity in the southern Indian Ocean and the Antarctic Oscillation?

Abstract

In this article, the relationship between the Antarctic Oscillation (AAO) and the tropical cyclone (TC) activity in the Southern Indian Ocean (SIO) was examined. It was found that, on the interannual time scale, the AAO is well linked with the TC activity in the SIO during TC season (December to March). The rank correlation coefficient between the AAO index and the TC frequency in the SIO is 0.37, which is significant at the 95% confidence level. When the AAO is in a positive phase, TC passage in the northwestern coast of Australia (100E°-120°E and 10°S-30°S) increases by approximately 50-100% from the climatology. The increase in the TC passage is primarily the result of more frequent TCs originating in this region due to an enhanced water vapor convergence and ascending motions, which are caused by a cyclonic height anomaly over the western coast of Australia associated with the positive AAO phases. In addition, the AAO-height co-variations, which are essential to the formation of the AAO-TC links in the SIO, were investigated through a historical climate simulation using the Community Climate System Model 4 from the Coupled Model Intercomparison Project Phase 5. The AAO-height links were well reproduced in the simulation. The similarity in the AAO-height links between the observation and the simulation supports the physical robustness of the AAO-TC links in the SIO.the TC activity in the SIO during TC season (December to March). The rank correlation coefficient between the AAO index and the TC frequency in the SIO is 0.37, which is significant at the 95% confidence level. When the AAO is in a positive phase, TC passage in the northwestern coast of Australia (100E°-120°E and 10°S-30°S) increases by approximately 50-100% from the climatology. The increase in the TC passage is primarily the result of more frequent TCs originating in this region due to an enhanced water vapor convergence and ascending motions, which are caused by a cyclonic height anomaly over the western coast of Australia associated with the positive AAO phases. In addition, the AAO-height co-variations, which are essential to the formation of the AAO-TC links in the SIO, were investigated through a historical climate simulation using the Community Climate System Model 4 from the Coupled Model Intercomparison Project Phase 5. The AAO-height links were well reproduced in the simulation. The similarity in the AAO-height links between the observation and the simulation supports the physical robustness of the AAO-TC links in the SIO.