On the relationships between the El Ni�o-Southern Oscillation and Australian land surface temperature

A comprehensive analysis of the linear covariability of Australian surface temperatures with the Southern Oscillation (SO) has been performed. Using newly available data, including high quality observational temperature analyses and the National Centres for Environmental Prediction (NCEP)/National Centre for Atmospheric Research (NCAR) reanalyses, it is shown that the SO plays a major role in the variability of seasonal maximum, minimum and mean temperature, and diurnal temperature range. The observed relationships are strongest over eastern Australia year round and over northern Australia during the summer half year. The SO–temperature correlations are comparable in magnitude with those described previously for Australian rainfall, but with a strong geographical and seasonal variation. This complexity cautions against the exclusive use of annual means, and has probably led to an underestimation of the importance of the SO for Australian temperature variability in earlier studies. It is shown that SO-related variations in the radiative and latent heat fluxes are largely responsible for the SO–temperature covariability. Variations of the sensible heat flux are primarily forced by changes in the surface temperature, and act to dampen the temperature signal. Variations of the short- and long-wave radiative fluxes tend to have a similar magnitude, but different signs, meaning that the primary radiative signal appears in the diurnal temperature range. The seasonal and spatial variations in radiative and latent heat fluxes are largely responsible for the complexities of the SO–temperature covariability. An analysis of the SO–temperature relationships at lag suggests that variations of Australian temperature associated with the SO are as predictable as those of Australian rainfall. There is evidence that the predictability of temperature is enhanced by variations in large-scale soil moisture, which is associated with SO–rainfall changes.