Indicator: Temperature & its variability

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What the results tell us for Tumut

Analysis, graphs and tables by

The official Bureau of Meteorology station in Tumut closed in 1994, and so temperature data for the long-term climate station at Tumut are not available and cannot be reviewed for the years 1997-2000.

It is useful to consider temperature in Tumut in the context of regional temperature patterns.

The climatological context for temperature in Tumut

The long-term perspective: Adelong

There are no distinct overall trends in annual temperature at Adelong over the 88-year record there. The decline in temperature around the 1950s and 1960s that is characteristic of other stations in the region may be present, but there are some significant gaps in the record that make detailed long-term analysis difficult. The graphs below show annual mean temperatures (the average of the monthly mean temperatures for all months in the year), annual mean maximum temperatures (the average of all the maximum temperatures), and annual mean minimum temperatures, all as deviations from the appropriate long-term average.

Figure 1. Adelong - annual mean temperature deviations Figure 2. Adelong - annual maximum temperature deviations Figure 3. Adelong - annual minimum temperature deviations Figure 4. Adelong - annual mean temperatures, showing maximum (top line), minimum (bottom line) and the range (dotted line in the middle - calculated as the difference between maximum and minimum temperatures)

Annual mean temperatures show a tendency to decline after about 1940, when they also become less variable. The decline seems to be a feature of the minimum rather than the maximum temperatures. Unfortunately there is an extended period without data in the 1950s and 1960s, and the record from the mid 1960s is not continuous. In appears that around 1980 there was a warmer spell of several years duration. The warmer spell of years around 1980 had both maximum and minimum temperatures tending to be above average, although maxima were more consistently high. Figure d shows that annual average maximum (top) and minimum (bottom) temperatures have generally fluctuated together at Adelong. There are no obvious trends in temperature, and the break in the record of about 10 years around 1960 makes detailed assessment difficult. There are also no obvious trends or changes in the temperature range - middle: the difference between maximum and minimum temperatures (Figure 4).

About the data

See also: Information about the analysis techniques used

The best available long-term temperature record in Tumut Shire is measured at the official Bureau of Meteorology station in Adelong. Data for this and other stations in the Shire may be made available through the Bureau of Meteorology. There may also be a number of privately-kept records in the Shire; these often contain invaluable information for otherwise sparsely-monitored areas.

The Adelong temperature record begins in 1907; unfortunately it ends in 1994. This is long enough for some climatological analyses, but low-frequency signals and trends may not emerge clearly. Long records from stations close to Tumut Shire (in Yass shire, for example) may also provide insights into the temperature climatology of the Shire.

Information on Bureau of Meteorology weather stations and climate data can be obtained by contacting the National Climate Centre in Melbourne:
Tel: (03) 9669 4082
Fax: (03) 9669 4515
Email: dstran@bom.gov.au
http://www.bom.gov.au

Description: What does 'temperature and its variability' measure?

Which data are collected?

• temperature statistics
• range of variability

Why do we report this indicator?

Temperature, along with rainfall, is one of the main factors that influences the nature and species composition of ecosystems, as well as the types of agricultural activities that can be carried out in the Australian Capital Region. It is the temperature extremes which are of most interest, as longer-term averages are slow to change in response to climate changes, both natural and human induced such as the enhanced Greenhouse effect. For example, many crops are vulnerable to an "unseasonally late" frost, or an extremely hot day at specific stages in crop growth.

Temperature also affects human comfort; this is reflected in energy usage, as many dwellings and places of work require some heating in the coldest winter months, and/or cooling in the hottest summer months.

There are several measures of temperature variability that can be used to provide information on the condition of the region's climate. These include:

• average annual temperature
• minimum and maximum temperatures averaged over the ten percent of highest and ten percent of lowest temperatures recorded in each year and in each season
• average daily temperature range.

Data for each of these are considered for the current reporting period, and for the longest period for which data are available; wherever possible they are compared to long-term mean values for the period 1961-1990.