A Southwest Pacific Tropical Cyclone Climatology and Linkages to the El Nino-Southern Oscillation

The new South Pacific Enhanced Archive for Tropical Cyclones (SPEArTC) dataset provides an opportunity to develop a more complete climatology of tropical cyclones (TCs) in the southwest Pacific. Here, spatial patterns and characteristics of TCs for the 41-yr period beginning with the 1969/70 season are related to phases of the El Nino-Southern Oscillation (ENSO), taking into account the degree of ocean-atmosphere coupling. Twentieth-century reanalysis data and the coupled ENSO index (CEI) were used to investigate TC genesis areas and climate diagnostics in the extratropical transition (ETT) region at and south of 25 degrees S during different CEI ENSO phases. This is the first study looking at CEI-based ENSO phases and the more detailed relationship of TCs to the coupling of the ocean and atmosphere during different ENSO phases. Consistent with previous findings, positive relationships exist among TCs, sea surface temperature, and atmospheric circulation. A statistically significant greater frequency of major TCs was found during the latter half of the study period (1991-2010) compared to the 1970-90 period, again consistent with the findings of other studies. Also found were significant and consistent linkages highlighting the interplay of TCs and sea surface temperature (SSTs) in the southwest Pacific basin west of 170 degrees E and a closer connection to atmospheric circulation east of 170 degrees E. Moreover, this study demonstrates subtle differences between a fully coupled El Nino or La Nina and atmospheric-or ocean-dominated phases, or neutral conditions.