Solar correlates of Southern Hemisphere mid‐latitude climate variability

Abstract

Atmospheric circulation in the southern mid-latitudes is dominated by strong circum-Antarctic zonal west winds (ZWW) over the latitude range of 35 to 60°S. These winds exhibit coherent seasonal and interannual variability, which has been related both to Antarctic (e.g. polar ice) and low-latitude climate (e.g. El Niño-southern oscillation) parameters. Historical and recent studies suggest that, at its northern margins, variability in the ZWW also has a marked quasi-decadal component. Analysis of sea-level pressure and rainfall data for the Australian region, South Africa and South America confirms frequent indications of quasi-decadal variability in parameters associated with the ZWW, which appears to be in phase around the hemisphere. This variation broadly correlates with the sunspot cycle, and specifically appears to reflect sunspot-correlated, seasonally modulated shifts in the latitude range each year of the sub-tropical ridge over eastern Australia. Sunspot-correlated variability in the southern mid-latitudes is likely to have substantial effects on temperate climate and ecology and is consistent with recent models of solar effects on upper atmospheric climate, though the mechanisms that link these to winds and rainfall at sea level remain obscure.

The latitude of the subtropical ridge over Eastern Australia: The L index revisited

“…Thresher (2002Thresher ( , 2003 The most recent calculation of an L index has been by Thresher (2002Thresher ( , 2003. The L index time series shown in Thresher (2003) is indicated as being derived from a mixture of the Das and Pittock indices up to 1977, and one calculated by Thresher from 'daily Australian Bureau of Meteorology (BoM) charts' from 1967 to the present.…”

“…Here, the variation of the latitude of the subtropical ridge over eastern Australian longitudes (approximately 150°E) is examined and compared with conclusions reported by Thresher (2002Thresher ( , 2003. Connections between this index and the large-scale hemispheric circulation as manifested by the annular mode or Gibson's (1992) latitude of the subtropical wind maximum will be examined in a later study.…”

“…There has been renewed interest in recent years in a number of these simple indices of the large-scale circulation over the Australian region (Thresher, 2002(Thresher, , 2003 with a view to improved understanding of climate anomalies, and hence seasonal forecasting and possible long-term climate change. On a larger scale, recent research has suggested possible links between variability and long-term trends in the high southern latitudes associated with the so-called southern annular mode (Thompson and Solomon, 2002) and Australian climate.…”

Depth-mediated reversal of the effects of climate change on long-term growth rates of exploited marine fish

“…The fit between summer (January-March) mean sea surface temperatures (SSTs) at Maria Island and a pooled growth rate time series for the three shallow-water species is good, capturing both the long-term trends and a suggestion of quasi-decadal oscillations in both data sets (see ref. 19) (Fig. 2a).…”

Lunar Tides and the Long-Term Variation of the Peak Latitude Anomaly of the Summer Sub-Tropical High Pressure Ridge over Eastern Australia

“…Pittock [16] has shown that the interannual variability of the latitude of the surface subtropical high pressure maximum over Eastern Australia is major mechanism influencing inter-annual rainfall variability. It has also been shown to be connected to the inter-annular variability of the annual mean maximum temperatures (Coughlan [17]), zonal westerly winds (Thresher [18]), meridional wind and mean air temperature, and ozone (Pittock [19]). …”