Different Modes of Variability over the Tasman Sea: Implications for Regional Climate

New climate mode for longterm drought

Network of dipole patterns for 1979-2011 based on SRNN method in (a) HadSLP2 and (b) MERRA SLP with normalized connection weights (gray shading) and correlation of each weighted area averaged time series with the SAM index (color shading). Dashed lines indicate no statistical significance at the 95% confidence interval. Insert: Northern and southern centers of the new teleconnection using the SRNN approach for each of the four seasons and annually.


A new Shared Reciprocal Nearest Neighbor (SRNN) approach is used to detect atmospheric teleconnections without being bound by orthogonality (such as Empirical Orthogonal Functions). This method employs negative correlations in a global dataset to detect potential teleconnections. One teleconnection occurs between the Tasman Sea and the Southern Ocean. It is related to the El Niño/Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), and the Southern Annular Mode (SAM). This teleconnection is significantly correlated with SAM during austral summer, fall and winter, with IOD during spring, and with ENSO in summer. It can thus be described as a hybrid between these modes. Given previously found relationships between IOD and ENSO, and IOD's proximity to the teleconnection centers, correlations to IOD are generally stronger than to ENSO.

Increasing pressure over the Tasman Sea leads to higher (lower) surface temperature over eastern Australia (southwestern Pacific) in all seasons, and is related to reduced surface temperature over Wilkes Land and Adélie Land in Antarctica during fall and winter. Precipitation responses are generally negative over New Zealand. For one standard deviation of the teleconnection index, precipitation anomalies are positive over Australia in fall, negative over southern Australia in winter and spring, and negative over eastern Australia in summer. When doubling the threshold, the size of the anomalous high-pressure center increases and annual precipitation anomalies are negative over southeastern Australia and northern New Zealand. Eliassen-Palm fluxes quantify the seasonal dependence of SAM, ENSO and IOD influences. Analysis of the dynamical interactions between these teleconnection patterns can improve prediction of seasonal temperature and precipitation patterns in Australia and New Zealand.

People: Liess, A. Kumar, Snyder, Kawale, Steinhaeuser, Semazzi, Ganguly, Samatova, V. Kumar