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Australian drought: the interference of multi‐spectral global standing modes and travelling waves
Author(s) -
White Warren B.,
McKeon Greg,
Syktus Jozef
Publication year - 2003
Publication title -
international journal of climatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.58
H-Index - 166
eISSN - 1097-0088
pISSN - 0899-8418
DOI - 10.1002/joc.895
Subject(s) - climatology , hindcast , predictability , environmental science , sea surface temperature , geology , quantum mechanics , physics
Abstract Extreme drought has devastated the flora, fauna, and regional economy in rangeland grazing districts over Australia for 3–5 years duration every 20 to 30 years throughout the 20th century. We investigate the source of drought occurring in five example grazing districts in eastern and central Australia. We find year‐to‐year variability in grazing district rainfall (GDR) during the summer rainy season (November to March) composed of quasi‐biennial, interannual, quasi‐decadal, and interdecadal signals from 1900 to 1999. However, the longer period signals dominate, accounting for the interdecadal quasi‐periodicity of the drought/flood cycle. We find these GDR signals associated with corresponding global standing modes and travelling waves in covarying sea‐surface temperature (SST) and sea‐level pressure (SLP) anomalies. These global SST/SLP modes/waves influence the GDR signals by altering the troposphere moisture flux converging onto the grazing districts from regional tropical and extra‐tropical oceanic source regions. We construct statistical models to determine whether the evolution of these global SST/SLP modes/waves over the oceanic source regions can hindcast corresponding GDR signals from one year to the next. When these models allow for modulation of the modes/waves, they hindcast ∼1/3 of the variance in the GDR indices at 1 year lead, including the drought episodes. We find drought resulting from the constructive interference of the dry phases of the quasi‐decadal and interdecadal global SST/SLP modes/waves, accompanied by a weakening of year‐to‐year variability associated with either weak quasi‐biennial and interannual modes/waves or their destructive interference. Copyright © 2003 Royal Meteorological Society