Presented at the 2013 Aquarius/SAC-D Science Team MeetingThis study analyzes time series of passive microwave data collected in Southern Hemisphere ecosystems of Australia and Argentina. We used AMSR-E, WINDSAT, AMSR2 and Aquarius/SAC-D data at L, X, and Ka bands, considering up to four observations per day at different local times. Two microwave indices (Frequency Index (FI(X and Ka bands, V polarization)) and Polarization Index (PI(X band, L Band))) were calculated, to link canopy and soil variables. Both seasonal and hourly variations of indices were observed. The FI(X and Ka bands) vs PI (X band) scheme was found the best approach to show the main biophysical processes involved. In dense vegetated areas both PI and FI mainly depend on the canopy properties. In areas characterized with intermediate LAI values, soil effects dominate FI and PI dynamics, due to soil moisture changes in sandy soils. Finally, in the less dense vegetated areas, FI mostly dependent on the complex dynamics of soil condition, and PI seasonality associated to phenology. These results are relevant, since vegetation and soil conditions are components of the overall water balance and surface radiation budget, which effectively modulates evapotranspiration.