Melbourne
Climate overview
Rainfall
Rainfall across the Melbourne region varied from average to below average, except for areas in the northeast and southeast which experienced above average rainfall for the 2013–14 year (Figure C1). The total area-averaged rainfall over the Melbourne region during the 2013–14 year was 845 mm, 2% below the long-term (1900–2014) area-averaged rainfall of 865 mm.
These conditions resulted in a 7% decrease in inflows to rivers and water storages during the 2013–14 year compared with the previous year. This decrease is likely to be a result of the generally dry soil conditions across most the region during the year and the pattern of rainfall throughout the year. As a result, a slight decrease of total storage volume at end of the 2013–14 year was observed (see Surface water assets in Supporting information). If there had not been an increase in the amount of water transferred into the region from the Thomson Reservoir, storage volumes within the region would have been further decreased at end of the 2013–14 year (see Water received under inter-region agreements in Supporting information).
Figure C1 Annual rainfall deciles for the Melbourne region during the 2013–14 year
Annual rainfall ranged from more than 1,200 mm in the northeast of the region to less than 500 mm in the southwest of the region including the western part of metropolitan Melbourne (Figure C2).
Figure C2 Total annual rainfall for the Melbourne region during the 2013–14 year
Rainfall was well below average in much of eastern Australia during the 2013–14 year, while rainfall was well above average in parts of southern and northern central Australia and the southeast coast. There were no strong influences from large-scale drivers during the reporting year, with a short-lived negative Indian Ocean Dipole event decaying at the start of the year. The El Niño-Southern Oscillation was also neutral for most of the year.
The area-averaged monthly rainfall was below the long-term average for December 2013 to March 2014 and May 2014 during the 2013–14 year (Figure C3). Above average or close to average rainfall was observed for the remaining months of the year. January 2014 was the driest month, recording just above the 10th percentile of long-term rainfall. June 2014 was the wettest month during the year, with 104 mm rainfall.
Figure C3 Total monthly rainfall for the Melbourne region during the 2013–14 year compared with the long-term average and percentiles for the region
Evapotranspiration
Potential evapotranspiration across the Melbourne region was generally average for the 2013–14 year (Figure C4); however, there were small areas with below average and above average conditions.
Figure C4 Annual evapotranspiration deciles for the Melbourne region during the 2013–14 year
The potential evapotranspiration estimate was produced by the Australian Water Resources Assessment system landscape model (AWRA-L) version 3.0 (Van Dijk 2010). The AWRA-L model uses a modified version of the Penman–Monteith method to produce the potential evaporation. Daily AWRA-L potential evaporation grids were produced based on daily gridded climate data that were available on a 0.050 (approximately 5 km) national grid.
The total area-averaged potential evapotranspiration over the Melbourne region during the 2013–14 year was 953 mm, which is marginally below the long-term area-averaged potential evapotranspiration of 968 mm (based on the 1970–2014 period). Potential evapotranspiration was highest in the eastern part of the region (Figure C5).
Figure C5 Total annual evapotranspiration for the Melbourne region during the 2013–14 year
Temperature
During the 2013–14 year, the entire Melbourne region experienced mean temperatures that were the highest on record based on temperature records for the 1911–2014 period (Figure C6).
Figure C6 Annual mean temperature deciles for the Melbourne region during the 2013–14 year
Mean temperatures across the Melbourne region ranged from more than 15°C in southern parts of the region to less than 12°C in isolated areas along the northeastern borders (Figure C7).
Figure C7 Annual mean temperature for the Melbourne region during the 2013–14 year
Monthly mean temperatures for the Melbourne region were above average for all months during the 2013–14 year (Figure C8). Monthly mean temperatures from October 2013 to April 2014 except January 2014 were marginally below the 90th percentile of long-term mean temperatures (1911–2014). Monthly mean temperatures for the other months were at or above the 90th percentile. September 2013 was the warmest September on record for the Melbourne region.
Figure C8 Monthly mean daily temperature for the Melbourne region during the 2013–14 year compared with the long-term average and percentiles for the region