About the deciles timeseries graphs

Analyses available

For each region of Australia the extent of extremely low or extremely high rainfall or temperature, with respect to the long-term average, is provided for each month, season and year. This information is presented as the fraction of the total area within each region that is ranked in the highest and lowest decile of the long-term timeseries.

Deciles are a convenient way of denoting thresholds within a frequency distribution. If we consider monthly rainfall, a frequency distribution is a table that sorts monthly rainfall amounts by category of similar occurrences over the length of the observing period. Thus, monthly rainfall amounts close to mean rainfall for that month, will have the highest number of occurrences, while those at the extreme ends of the frequency distribution will have the least number of occurrences. Decile 1 (the lowest decile) represents the lowest 10 percent of rainfall totals, ranked against all other rainfall totals for that period. Decile 10 (the highest decile) represents the highest 10 percent of rainfall totals by the same ranking.

The rainfall and temperature decile timeseries represent the fraction (percentage) of total area that is experiencing historically low (Decile 1) or historically high (Decile 10) rainfall or temperature.

Australian and regional decile timeseries are available from 1900 for rainfall and 1911 for temperature for annual, seasonal and monthly periods, as well as for the southern (April–November) and northern (October–April) wet seasons. Prior to 1900 Australia's rainfall network was too sparse for reliable analyses. Prior to 1910 Australia's standardised temperature network was too sparse for national analyses.

Note that even though the timeseries are updated each month, values for recent months should be considered preliminary as it can take several months to fully enter and quality-check all available data into the database, especially for rainfall.

Fraction of total area (percent) decile values are provided for each of the six Australian States and the Northern Territory, all of Australia, and six climatologically distinct regions: northern Australia (north of 26°S), southern Australia (south of 26°S), southwestern Australia (southwest of the line joining 30°S, 115°E and 35°S,120°E), southeastern Australia (south of 33°S, east of 135°E), eastern Australia (Queensland, New South Wales, Victoria and Tasmania), and the Murray–Darling catchment. Values calculated for New South Wales include the Australian Capital Territory. A listing of the values for percent of area in deciles 10 and 1 can be obtained from the "Download" link above the graph, either in sorted (smallest to largest) or raw (chronological order) versions.

Timeseries are determined for each Australian State, the Northern Territory and the six regions shown above

Data used

Mean decile timeseries are calculated using gridded datasets based on all available monthly rainfall totals and the temporally homogenised ACORN-SAT temperature dataset. More detail about the rainfall dataset can be obtained from the Rainfall Map Information page, while the relevant scientific reference paper is Jones et al. (2009). More detail about the temperature dataset, ACORN-SAT, including the relevant scientific reference papers and downloadable data, can be obtained from the ACORN-SAT portal.

Please note that any use of these data should be acknowledged to the Bureau of Meteorology. Apart from the purposes of study, research, criticism and review, no part of these data may be reproduced, or redistributed for any commercial purposes, or distributed to a third party for such purpose, without written permission from the Director of Meteorology.

A listing of the values displayed in each graph can be obtained from the "Download" link above the graph, either in sorted (smallest to largest) or raw (chronological order) versions. The format for these data is:

    <start year><start month><end year><end month> <mean rainfall value (mm)>

The "Sorted dataset" link provides the timeseries as a sorted list in order to place recent values in historical context.

Rainfall network

Representative locations of rainfall stations included in spatial averages