Can Australian multiyear droughts and wet spells be generated in the absence of oceanic variability?
Taschetto, Andrea S.
Sen Gupta, Alexander
Ummenhofer, Caroline C.
England, Matthew H.
MetadataShow full item record
KeywordCirculation/ Dynamics; Atmosphere-ocean interaction; Atm/Ocean Structure/ Phenomena; Drought; Precipitation; Physical Meteorology and Climatology; Climate variability; Forecasting; Climate prediction; Variability
Anomalous conditions in the tropical oceans, such as those related to El Niño–Southern Oscillation and the Indian Ocean dipole, have been previously blamed for extended droughts and wet periods in Australia. Yet the extent to which Australian wet and dry spells can be driven by internal atmospheric variability remains unclear. Natural variability experiments are examined to determine whether prolonged extreme wet and dry periods can arise from internal atmospheric and land variability alone. Results reveal that this is indeed the case; however, these dry and wet events are found to be less severe than in simulations incorporating coupled oceanic variability. Overall, ocean feedback processes increase the magnitude of Australian rainfall variability by about 30% and give rise to more spatially coherent rainfall impacts. Over mainland Australia, ocean interactions lead to more frequent extreme events, particularly during the rainy season. Over Tasmania, in contrast, ocean–atmosphere coupling increases mean rainfall throughout the year. While ocean variability makes Australian rainfall anomalies more severe, droughts and wet spells of duration longer than three years are equally likely to occur in both atmospheric- and ocean-driven simulations. Moreover, they are essentially indistinguishable from what one expects from a Gaussian white noise distribution. Internal atmosphere–land-driven megadroughts and megapluvials that last as long as ocean-driven events are also identified in the simulations. This suggests that oceanic variability may be less important than previously assumed for the long-term persistence of Australian rainfall anomalies. This poses a challenge to accurate prediction of long-term dry and wet spells for Australia.
Author Posting. © American Meteorological Society, 2016. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 29 (2016): 6201-6221, doi:10.1175/JCLI-D-15-0694.1.
Suggested CitationArticle: Taschetto, Andrea S., Sen Gupta, Alexander, Ummenhofer, Caroline C., England, Matthew H., "Can Australian multiyear droughts and wet spells be generated in the absence of oceanic variability?", Journal of Climate 29 (2016): 6201-6221, DOI:10.1175/JCLI-D-15-0694.1, https://hdl.handle.net/1912/8453
Showing items related by title, author, creator and subject.
Wintertime atmospheric response to North Atlantic Ocean circulation variability in a climate model Frankignoul, Claude; Gastineau, Guillaume; Kwon, Young-Oh (American Meteorological Society, 2015-10-01)Maximum covariance analysis of a preindustrial control simulation of the NCAR Community Climate System Model, version 4 (CCSM4), shows that a barotropic signal in winter broadly resembling a negative phase of the North ...
Climate variability in the equatorial Pacific Ocean induced by decadal variability of mixing coefficient Huang, Chuan Jiang; Wang, Wei; Huang, Rui Xin (American Meteorological Society, 2007-05)The circulation in the equatorial Pacific Ocean is studied in a series of numerical experiments based on an isopycnal coordinate model. The model is subject to monthly mean climatology of wind stress and surface thermohaline ...
Multidecadal Indian Ocean variability linked to the Pacific and implications for preconditioning Indian Ocean dipole events Ummenhofer, Caroline C.; Biastoch, Arne; Böning, Claus W. (American Meteorological Society, 2017-02-15)The Indian Ocean has sustained robust surface warming in recent decades, but the role of multidecadal variability remains unclear. Using ocean model hindcasts, characteristics of low-frequency Indian Ocean temperature ...