About the temperature timeseries graphs

Analyses available

Australian and regional temperature timeseries are available from 1910 to present (prior to 1910 Australian temperature observations are sparse and some were measured in non-standard ways).

Note that temperature timeseries are presented as anomalies or departures from the 1961–1990 average because temperature anomalies tend to be more consistent throughout wide areas than actual temperatures. Climatology (average temperature) is calculated over the 1961–1990 period, and are provided for the selected temperature variable, period and region. For instance, the climatology for summer is formed from the December, January and February monthly climatology values, each over 1961–1990. The period 1961 to 1990 is the current international standard period for the calculation of climate averages.

Separate timeseries are available for maximum, mean and minimum temperature as well as diurnal temperature range (DTR). Mean temperatures are the simple average of the maximum and minimum temperatures while DTR represents the difference between maximum and minimum temperatures.

Area average temperature timeseries 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.

Australian regions used in timeseries

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

The actual data values used to produce each graph are available via the "Raw dataset" link. The format for these data is:

    <start year><start month><end year><end month>   <temperature anomaly (°C)>

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

Data used

The temperature timeseries are calculated from a homogeneous temperature dataset (known as the Australian Climate Observations Reference Network-Surface Air Temperature, or ACORN-SAT, dataset) developed for monitoring climate variability and change in Australia. The dataset employs the latest analysis techniques and takes advantage of newly digitised observational data to provide a daily temperature record over the last 100 years. This data will enable climate researchers to better understand long-term changes in monthly and seasonal climate, as well as changes in day-to-day weather.

Calculating average temperatures

Calculating the average temperatures for Australia, the states and the regions, requires the use of an intermediate gridded dataset on a 5 km (0.05° × 0.05°) resolution grid, based on the ACORN-SAT dataset. Starting with the daily timeseries, monthly averages of station temperature are calculated. If more than 10 days of data are missing in a given month, that monthly average is deemed to be missing, and is not used in subsequent calculations. Monthly normal values (1981–2010 averages) calculated for each station are subtracted from the monthly station temperature data. The resulting monthly temperature anomalies (departures from the normal value) are interpolated to the 5 km spatial grid using the Barnes successive correction techniques to obtain the monthly temperature anomalies for all of Australia. To ensure that the spatial grid is representative of the large-scale climate, the ACORN-SAT urban sites are excluded from this analysis. The national and regional means are calculated from area-weighted averages of the grid-point anomalies, having been renormalised to a 1961–1990 gridded climatology. The Australian and regional seasonal and annual anomalies are calculated as arithmetic averages of their respective monthly average anomaly.

Station weights

Calculating the average temperature anomaly with this technique has the effect of weighting each location value according to how large its 'footprint' is. The footprint reflects the relative influence that a single station has on the national dataset as a consequence of its remoteness or proximity to neighbouring stations. Locations in regions with widely spaced observations (mostly remote areas) have a larger footprint in the analysis than locations in more densely observed areas. To capture this process in a simple form, station weights ('footprints') for monthly maximum and minimum Australian average temperature are calculated as the fraction of the Australian land area which is closest to each station.
Station weights for non-urban ACORN-SAT stations: Maximum temperature, Minimum temperature

Temperature network

Representative station locations used for ACORN-SAT dataset

Representative locations of ACORN-SAT temperature stations. Urban stations are not included in spatial averages.

Further information

More information about the dataset, including additional data, station details, the methods used and a peer review of the dataset can be found on the ACORN-SAT page.

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.

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