The Interannual and Interdecadal Variability in Hurricane Activity

Abstract

While the interannual variability of hurricane activity has been studied extensively over the last few decades, there has been a recent increase in the interest of the interdecadal variability of hurricane activity (e.g., Henderson-Sellers et al. 1998; Emanuel, 2005; Webster et al. 2005; Schultz, 2007; Lupo et al. 2008; Ng and Chan, 2010) worldwide. This interest has been prompted by several active hurricane years in the Atlantic Ocean basin, the occasional occurrence of tropical cyclones in the South Atlantic in the last decade (e.g. Reagan et al. 2005; McTaggart-Cowan et al. 2006), as well as concern about changes in hurricane frequency that may be a result of changes in Earth’s climate. These active years in the Atlantic which garnered much media attention included the 2004 season during which several storms struck the Southeast United States including Florida, and the 2005 season which was the most active hurricane season since 1933, and included the deadly hurricane Katrina. Some studies, e.g., Lupo and Johnston (2000) (hereafter LJ00), and then Lupo et al. (2008), suggested that there is significant interdecadal variability in the occurrence and intensity of Atlantic region hurricane activity, and that this variability may be linked to the Pacific Decadal Oscillation (PDO). More specifically, these studies found that there was a change in the behavior of interannual variability of tropical cyclone (TC) occurrences in the North Atlantic as related to the El Nino and Southern Oscillation (ENSO). During the negative phase of the PDO (1947-1976), they found little ENSO related variability in the number and intensity of hurricanes basin wide. However, during the positive phase of the PDO (1977 – 1999) they found that there was strong interannual variability in TC occurrences between El Nino and La Nina years. During La Nina years, there were more and stronger hurricanes overall even though there were fewer months with significant hurricane activity. Also, there were more Caribbean and Gulf region hurricanes during La Nina years. Additionally, studies have shown that since 1999 (see Lupo et al. 2007, 2008, and Birk et al. 2010), the Pacific Ocean basin region has reverted back to the negative phase of the PDO. Recently, Vimont and Kossin (2007) (and Kossin and Vimont, 2007) found a strong correlation in the North Atlantic between accumulated cyclone energy (which is positively correlated with TC activity) and the Atlantic Meridional Mode (AMM). In their work, they also find that the Atlantic Multi-decadal Oscillation (AMO) may excite the AMM on a