Bureau weather stations record a variety of aspects of the weather including temperature, humidity, rainfall, air pressure, sunshine, wind speed and direction, cloud and visibility. Stations which measure rainfall are the most common. The earliest data present in the Bureau's database of weather observations are from the 1830s (at Adelaide West Terrace, Parramatta, Port Arthur, and Colombo Creek). Since that time the number of stations has grown significantly; more than seven thousand stations are currently open, and over the history of the Bureau observations have been taken at over twenty thousand locations.
In addition to the weather and rainfall network, there are a number of other networks designed for specific purposes. For example, around 5600 stations have at some point contributed observations to the Bureau's flood warning network. The Bureau's solar ground observing network provides high quality data to detect small changes in the solar radiation climate, as well as calibrating our solar data obtained from satellite. Other networks include upper air, marine, sea level, and tsunami alert monitoring stations.
Station locations cover a wide range of environments; from open desert areas to the top of mountains, urban streets, offshore islands and Antarctic ice sheets. The characteristics of these sites can influence the observations being made. For example, consider an open area surrounded by trees. This is likely to make a very good rainfall site, because the trees would help to reduce the wind turbulence above the rain gauge which can affect the amount of rain being recorded. However, it is not likely to be a good wind observation site. While siting guidelines exist for the location of instruments to minimise impacts of the surrounding terrain, the final location is often a compromise between a wide range of factors.
While the basic weather elements observed have remained the same, the instruments used have improved over time, particularly with the introduction of automatic weather stations. Each instrument can be characterised by a set of parameters, including range, linearity and uncertainty. In many cases the differences in observations of an element taken with various types of instruments are not likely to be significant. However, instrument characteristics may need to be considered for specialist applications such as the study of long-term trends in the climate. Details of observing instruments can be found in the station metadata file, including the type of an instrument and when it was installed.