Sunshine hours were close to average in 2000 and exceeded that value in 2001 and 2002, as shown in Table 1. The largest anomaly was reported in 2002, when the annual average was 10.7% above the long-term mean at 8.4 hours per day.
|Table 1. Annual sunshine statistics in the ACT, 2000–02|
|Annual mean (hours/day)||7.6||7.8||8.4|
|Anomoly (% of long-term mean)||+0.1||+2.7||+10.7|
Monthly average sunshine hours at Canberra Airport were above normal in the majority of months during the period January 2000 to June 2003 (Figure 1). There was a marked degree of variability in the first part of this time, followed by a prolonged period of above-average sunshine from autumn 2002 (April) to summer 2003 (January). The unusually large amount of sunshine received during this period, together with reduced rainfall, higher than normal temperatures and increased evaporation and wind speeds, contributed to the drought conditions in the ACT region at the time.
Figure 1. Monthly sunshine anomalies at Canberra Airport, January 2000 to June 2003 (in hours/day)
Only 11 months (26%) in the period January 2000-June 2003 recorded below-average sunshine hours. The largest negative anomalies occurred in March and November 2000; the latter had the highest number of rain days for November on record at Canberra, with increased cloudiness accounting for the reduction in sunshine hours. February 2002, another wet month, also had anomalously low sunshine hours. The largest positive sunshine anomalies were recorded during winter and spring 2002, when values between 1.5 and 2.0 standard deviations above normal occurred in the five months from June to October 2002.
The least sunshine was received in July 2001, which had an average of 5.1 hours per day (the July average is 5.6, so this was not a significant anomaly). The largest monthly average of daily sunshine was recorded in December 2000 (11.1 hours per day—December is the sunniest month, with an average of 9.4 hours per day); the next highest was the hot, dry January of 2003, with 9.9 hours per day (compared to the long-term mean of 9.3 hours per day).
Sunshine hours at Canberra Airport tended to be above-average early in the record, followed by a period of generally below-average sunshine. From 1992 the ACT has received more than average annual sunshine in most years, with the highest annual average daily sunshine hours received in 2002.
Figure 2. Annual average sunshine hours at Canberra Airport from 1943 to 2002. The long-term (1978–2002) average is indicated by the horizontal line through the centre of the graph (scale in hours/day)
- The highest average of daily sunshine hours was recorded in 2002, with 8.4 hours per day. This should be considered in the context of the long-term mean and the seasonal range: the long-term mean for Canberra is 7.6 hours per day, and the range within the year is from a maximum of 9.4 hours per day in December to a minimum of 5.2 hours per day in June. In 2002 it was winter that was unusually sunny; summer sunshine was close to normal (Figure 3).
- The least sunshine on average (6.6 hours per day) was received in 1992, due to reductions in the amount of sunshine in both summer and winter, but predominantly in the wet summer of that year (Figure 3). There seems to have been a shift from above-average sunshine receipts in summer and less than average sunshine in winter, to sunnier winters and cloudier summers since 1992
Figure 3. Seasonal average sunshine hours at Canberra Airport from 1979 to 2002, expressed as standardised departures from the long-term mean for the period 1979–2002.
Analysis, graphs and tables by Dr Janette Lindesay, School of Resources, Environment and Society, The Australian National University.
Sunshine has been measured for an extended period of time at only one official Bureau of Meteorology station in the ACT, located at Canberra Airport. The record there begins in 1942, with the first complete year of observations in 1943. Other organisations (e.g. ACTEW, CSIRO and ACT Parks and Wildlife) may make independent measurements relevant to the area; their data may be made available independently, or through the Bureau of Meteorology. Most of these records are of considerably shorter duration, but often contain invaluable information for otherwise sparsely-monitored areas.
Information on Bureau of Meteorology weather stations and climate data can be obtained from:
|Organisation||National Climate Centre|
|Phone (BH)||(03) 9669 4082|
|Fax||(03) 9669 4515|