Interdecadal Variability of Intense Tropical Cyclone Activity in the Southern Hemisphere


Kevin Cheung

11:35:00 - 12:00:00

101 , Mathematics Research Center Building (ori. New Math. Bldg.)

The variability of intense tropical cyclone (TCs) in the Southern Hemisphere and its relation with large-scale environmental parameters using principal component analysis (PCA) are examined. The results show that there was a shift from low intense TC activity during 1976/77- 1987/88 (period 1) to high activity during 1988/89-2007/08 (period 2), which is related to more occurrences of intense TCs in the southwestern Indian Ocean (SWIO) and northwestern Australian region during period 2. There are distinct sea surface temperature anomaly (SSTA) dominating patterns based on T-mode PCA in period 1 and period 2, with the five dominating ones in period 2 having higher SSTA in the TC development regions. The temporal variability of the vertical wind shear (VWS) over IO is also examined through S-mode PCA. The second mode shows high VWS during the 1970s to early 1980s, followed by low VWS afterward during period 2, which may be responsible for the shift in intense TC activity over the IO. Linear correlative analysis shows that this VWS mode of variability is significantly related to the subtropical dipole events in the southern IO, which critical in determining the large-scale atmospheric and oceanic conditions for intense TCs to develop over the basin.

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