How Oceanic Oscillation Drives Soil Moisture Variations over Mainland Australia An Analysis of 32 Years of Satellite Observations

• Published in: Journal of climate Vol. 26; no. 24; pp. 10159 - 10173
• Main Authors: Bauer-Marschallinger, Bernhard, Dorigo, Wouter A., Wagner, Wolfgang, van Dijk, Albert I. J. M.
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 01.12.2013
• Subjects: Annual variations; Antarctic Oscillation; Atmospheric oscillations; Australia; Climate; Climate change; Climatology. Bioclimatology. Climate change; Datasets; Dipoles; Drought; Earth, ocean, space; El Nino; El Nino phenomena; El Nino-Southern Oscillation event; Empirical analysis; Exact sciences and technology; External geophysics; Humidity; Hydrologic cycle; Hydrology; Marine; Meteorology; Moisture effects; Ocean circulation; Oceanic oscillations; Orthogonal functions; Oscillations; Precipitation; Rain; Remote sensing; Satellite observation; Satellites; Seasons; Soil moisture; Soil moisture variations; Soil surfaces; Soil water; Southern Oscillation; Spring; Spring (season); Statistical variance; Studies; Summer; Time series; Variance; Variation; Winter; Australia; Indian Ocean; Southern Hemisphere; ISW, Indian Ocean; time series analysis; Teleconnection; El Niño Southern Oscillation; soil moisture; Indian ocean dipole; Australasia; Space remote sensing; Southern Hemisphere annular mode; Empirical orthogonal function; inundations; Satellite observation; ocean-atmosphere interaction; El Nino; drought; Observation data; Natural hazards
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/JCLI-D-13-00149.1

Australia is frequently subject to droughts and floods. Its hydrology is strongly connected to oceanic and atmospheric oscillations (climate modes) such as the El Niño–Southern Oscillation (ENSO), Indian Ocean dipole (IOD), and southern annular mode (SAM). A global 32-yr dataset of remotely sensed surface soil moisture (SSM) was used to examine hydrological variations in mainland Australia for the period 1978–2010. Complex empirical orthogonal function (CEOF) analysis was applied to extract independent signals and to investigate their relationships to climate modes. The annual cycle signal represented 46.3% of the total variance and a low but highly significant connection with SAM was found. Two multiannual signals with a lesser share in total variance (6.3%and 4.2%) were identified. The first one had an unstable period of 2–5 yr and reflected an east–west pattern that can be associated with ENSO and SAM but not with IOD. The second one, a 1- to 5-yr oscillation, formed a dipole pattern between the west and north and can be linked to ENSO and IOD. As expected, relationships with ENSO were found throughout the year and are especially strong during southern spring and summer in the east and north. Somewhat unexpectedly, SAM impacts strongest in the north and east during summer and is proposed as the key driver of the annual SSM signal. The IOD explains SSM variations in the north, east, and southeast during spring and also in the west during winter.