| Summary: | Global studies have shown that there is a widening of the tropics and a poleward expansion of the Southern Hemispheric Hadley Circulation in the mid-latitudes (Seidel et al., 2007), and a marked poleward displacement of the Southern Hemisphere westerly wind and storm front tracks over the Southern Ocean (Thompson and Solomon, 2002), and related wave fields (Young et al., 2011, Hemer et al., 2010). The behaviour of the Subtropical Ridge is unclear with some studies showing pressure intensification but there appears to be no significant poleward shift in its core location (Timbal and Drosdowski, 2012). These often quoted trends are more complex when viewed on a seasonal time scale, while at decadal scale they include the effects of the mid-1970s climate shift. The latitude of the STR is an important driver of Tasman Sea wave climate, effectively dividing the region into Easterly vs Westerly generated wind-waves. We present a synoptic typing of wave climate clustered against the latitude of the STR parameter. We examine the relationship between modal wave climate and the STR on seasonal to decadal timescales using instrumental waverider buoy data and ERA-INT reanalysis data. We also apply the approach to eight storm wave types, previously identified (Shand et al., 2011) and large scale drivers (Browning and Goodwin, 2013), and discuss the observed trends in the frequency of storm wave types with respect to the STR variability.
|
|---|