Influence of Sea Surface Warming on Long-Term Changes of Atlantic Tropical Cyclone Formation

Despite the observed high correlation between the Atlantic sea surface temperature (SST) and the Atlantic tropical cyclone (TC) activity, interpretation of this relationship remains unconvincing by now. This study suggests that the tropical Atlantic SST warming induces a pair of anomalous low-level cyclones on each side of the equator, providing favorable conditions for enhancing TC formation east of 45°W, while the combined effect of SST warming in the tropical Indian Ocean and Pacific tends to suppress the TC formation. Over the past 30 years (1978-2007) the TC activity in the Atlantic basin is characterized with significant enhancement of TC formation east of 45ºW, where the total TC number increased significantly compared to the period 1948-1977. Despite the possible undercount of TCs, this study shows that the recently enhanced TC formation may not be totally accounted for by the poor TC observing network prior to the satellite era. The Atlantic SST warming occurred in recent decades might have allowed more TCs forming, forming earlier, and taking a longer track, while the effect is partially offset by the SST warming in Indian and Pacific oceans. This study suggests that the close relationship between the Atlantic SST and TC activity over the past 30 years, including basin-wide increases in the average lifetime, annual frequency, proportion of intense hurricanes, and annual accumulated power dissipation index (PDI), as reported in previous studies, is mainly a competing result of the SST warming in Atlantic, Indian and Pacific oceans. The results agree with recent argument that the relative Atlantic SST warming or the SST difference between the tropical Atlantic and other oceans play an important role in controlling long-term TC activity in the Atlantic basin.