ACT State of the Environment 2007
During the reporting period, the weather in the ACT was generally warmer and drier than the average (1961–90) with all indicators being consistent with this warming and drying trend.
At Canberra International Airport rainfall was above average in only one year (2005) while 2004, 2006 and 2007 were considerably drier than normal. This was also reflected in the number of rain days per year; 2006 recorded the third lowest number of rain days on record.
A continued increasing trend was evident over the reporting period in both mean daily maximum and minimum temperatures. The years 2004, 2005, 2006 and 2007 were consecutively the hottest years recorded in Canberra in terms of the mean daily temperature (average of mean daily maximum and minimum temperatures), with each exceeding the record of the previous year. However, the recorded temperatures in 2007 may be higher than would have been observed if the weather station had remained undisturbed. A car park built immediately adjacent to the weather station may be altering the temperature characteristics near the site, which poses problems for its continued use as a long-term climate station.
Significant weather-related events that affected the ACT during this period were:
- Bushfires burnt out 70% of the ACT in January 2003. Over 500 houses were destroyed, four people died, and Namadji National Park was burnt out.
- Severe thunderstorms following the fires, in February 2003, in the Brindabella Ranges caused silting of the ACT water storages which had ramifications on water quality and created the need to build a water filtration unit, at great expense.
- Recovery of flora after the bushfires, combined with three very dry years, had a major impact on inflows into ACT water storages and resulted in the government implementing Level 3 water restrictions in 2006.
- Severe thunderstorm activity increased across the Territory during summer 2006–07 (Table 2). In particular, the severe thunderstorm over the Australian National University and Canberra City on the evening of 27 February 2007 caused considerable damage as a result of the large amount of hail that fell.
|Annual rainfall (mm)||623.2||569.2||435.2||648.6||361.2||565.8|
|Mean daily maxT (°C)||19.5||20.2||21||21||21.7||21.2|
|Mean daily minT (°C)||6.5||7.3||7||7.2||7||8.3|
|Mean daily meanT (°C)||13||13.7||14||14.2||14.4||14.8|
|Mean daily sunshine||7.6||7.9||8.3||8.2||8.5*||8.1|
|Mean daily evaporation||4.6||4.6||5.0||4.8||5.4||4.9|
|Mean hourly wind run/day||8.2||8.6||8.0||7.6||8.0||7.7|
Source: Bureau of Meteorology
|Days 35°C or more||5||6||14*||12||13||8|
|Days 30°C or more||30||38||45||48||64*||54|
|No. strong wind days||26||35||39||25||32||31|
|No. rain days||105||115||84||109||69||102|
|Mean daily pressure||1016.7||1017.5||1016.6||1017.3||1019||1017.3|
Has development around Canberra International Airport adversely affected its use as a climate reference station?
Canberra International Airport is one of the observation sites the Bureau of Meteorology uses as a climate reference station to measure climate change across Australia. The site commenced operation in March 1939 and remained relatively unchanged until 2005.
Developments in 2005 included construction of a hangar to the northwest of the observation site and new buildings and a car park to the north and east of the site during 2006–07. The edge of the car park is now only meters from the eastern boundary of the observation site. The question that has arisen as a result of these developments is: How much do these developments affect the Bureau's ability to keep using this site as a long-term reference station?
The results of cross comparisons of daily maximum and minimum temperatures between the observation site at Canberra International Airport and the Tuggeranong Automatic Weather Station suggest there could be an effect at Canberra International Airport on maximum and minimum temperatures as a result of development adjacent to the site thus impacting on its continued use as a climate reference station. However, it should be noted that this study is based on only one full year after development was completed and more data is needed to confirm these trends.
While there are moves to relocate the observation site to where any effect from the car park is reduced, it is considered essential that there be at least a 12-month overlap of observations once the site has been moved to enable meaningful comparisons to be made between all sites.
On the evening of 27 February 2006, a severe thunderstorm passed over central Canberra. The resulting extreme hail that fell covered the streets, stripped leaves from trees and caused considerable damage to buildings and infrastructure, especially at the Australian National University where around 70 buildings were damaged and greenhouses were destroyed; and in Civic Centre where many retail outlets sustained damage and were closed for trading for an extended period. Figure 1 is the Bureau of Meteorology radar display indicating the severity of the storm.
Note: EDST = eastern daylight saving time; Source: Bureau of Meteorology
All data comes from the Bureau of Meteorology