Abstract
Using 79 years (1913-1991) of Australian monthly precipitation data we
examined the nature of the persistence of rainfall anomalies. Analyses were
performed for four climate regions covering the country, as well as for the entire
Australian continent. We show that rainfall over these regions has high temporal
variability and that annual rainfall amounts over all five sectors vary in phase
and
are, with the exception of the north-west region, significantly correlated with
the
Southern Oscillation Index (SOI). These relationships were particularly strong
during the spring season. It is demonstrated that Australian rainfall exhibits
statistically significant persistence on monthly, seasonal, and (to a limited
extent)
annual time-scales, up to lags of 3 months and one season and 1 year. The
persistence showed strong seasonal dependence, with each of the five regions
showing memory out to 4 or 5 months from winter and spring. Many aspects of
climate in the Australasian region are known to have undergone considerable
changes about 1950. We show this to be true for persistence also; its
characteristics
identified for the entire record were present during the 1951-1980 period, but
virtually disappeared in the previous 30-year period. Much of the seasonal
distribution of rainfall persistence on monthly time-scales, particularly in the
east,
is due to the influence of the SOI. However, most of the persistence identified in
winter and spring in the north-west is independent of the ENSO phenomenon.
Rainfall anomalies following extreme 'dry' and 'wet' months, seasons and years
(lowest and highest two deciles) persisted more than would be expected by chance.
For monthly extreme events this was more marked in the winter semester for the
'wet events', except in the south-east region. In general, less persistence was
found
for the extreme seasons. Although the persistence of dry years was less than would
have been expected by chance, the wet years appear to display persistence. (C)
1997 by the Royal Meteorological Society. [References: 52]
PERSISTENCE CHARACTERISTICS OF AUSTRALIAN
RAINFALL ANOMALIES (VOL 17, PG 597, 1997). [Correction, Addition]
International Journal of Climatology. 17(8):908, 1997 Jun 30.