TRMM-TMI satellite observed soil moisture and vegetation density (1998-2005) show strong connection with El Nino in eastern Australia

Spatiotemporal patterns in soil moisture and vegetation water content across mainland Australia were investigated from 1998 through 2005, using TRMM/TMI passive microwave observations. The Empirical Orthogonal Function technique was used to extract dominant spatial and temporal patterns in retrieved estimates of moisture content for the top 1-cm of soil (theta) and vegetation moisture content (via optical depth tau). The dominant temporal theta and tau patterns were strongly correlated to the El Nino Southern Oscillation Index (SOI) in spring (r(2) = 0.90), and to a progressively lesser extent autumn, summer and winter. The Indian Ocean Dipole (IOD) index also explained part of the variation in spring theta and tau. Correlation analysis suggested that the regions most affected by El Nino are mainly located in eastern Australia. The results suggest that the drought conditions experienced in eastern Australia since 2000 and clearly expressed in these satellite observations have a strong connection with El Nino.