South Australian rainfall variability and climate extremes |
| |
| Authors: | Alexander D Evans John M Bennett Caecilia M Ewenz |
| |
| Institution: | (1) School of Chemistry, Physics and Earth Sciences, Flinders University of South Australia, GPO Box 2100, Adelaide, SA, 5001, Australia |
| |
| Abstract: | Rainfall extremes over South Australia are connected with broad-scale atmospheric rearrangements associated with strong meridional
sea surface temperature (SST) gradients in the eastern Indian Ocean. Thirty-seven years of winter radiosonde data is used
to calculate a time series of precipitable water (PW) and convective available potential energy (CAPE) in the atmosphere.
Principle component analysis on the parameters of CAPE and PW identify key modes of variability that are spatially and seasonally
consistent with tropospheric processes over Australia. The correlation of the leading principle component of winter PW to
winter rainfall anomalies reveal the spatial structure of the northwest cloudband and fronts that cross the southern half
of the continent during winter. Similarly the second and third principle components, respectively, reveal the structures of
the less frequent northern and continental cloudbands with remarkable consistency. 850 hPa-level wind analysis shows that
during dry seasons, anomalous offshore flow over the northwest of Australia inhibits advection of moisture into the northwest,
while enhanced subsidence from stronger anticyclonic circulation over the southern half of the continent reduces CAPE. This
coincides with a southward shift of the subtropical ridge resulting in frontal systems passing well to the south of the continent,
thus producing less frequent interaction with moist air advected from the tropics. Wet winters are the reverse, where a weaker
meridional pressure gradient to the south of the continent allows rain-bearing fronts to reach lower latitudes. The analysis
of SSTs in the Indian Ocean indicate that anomalous warm (cool) waters in the southeast Indian Ocean coincide with a southward
(northward) shift in the subtropical ridge during dry (wet) seasons. |
| |
| Keywords: | Principle component analysis Rainfall variability Climate extremes |
| 本文献已被 SpringerLink 等数据库收录！ |
|
