Perth
Climate overview

Rainfall

Rainfall across the Perth region was generally equivalent to average conditions for the 2013–14 year (Figure C1). The total area-averaged rainfall over the Perth region during the year was 777 mm, which is slightly below the long-term area-averaged rainfall of 800 mm (based on the 1900–2014 period).

These rainfall conditions represent an increase in rainfall compared to the 2012–13 year when rainfall was well below average (see the 2013 Account). The increased rainfall during the year contributed to increased flows in the major river systems in the region (see Water overview) and increased inflows into the major water storages (see the Surface water note).

 

Figure C1 Annual rainfall deciles for the Perth region during the 2013–14 year
Figure C1 Annual rainfall deciles for the Perth region during the 2013–14 year

 

Annual rainfall ranged from more than 900 mm in the southern and central parts of the region to less than 400 mm in the far southeast (Figure C2). 

 

Figure C2 Total annual rainfall for the Perth region during the 2013–14 year
Figure C2 Total annual rainfall for the Perth region during the 2013–14 year

 

Generally average to below average rainfall was experienced across much of Australia's southwest coast during the 2013–14 year. There were no strong influences from large-scale climate drivers during the year. Conditions in the Pacific Ocean were neutral and a short-lived negative Indian Ocean Dipole event, which developed towards the end of last year, decayed at the start of the 2013–14 year. The El Niño-Southern Oscillation was also neutral for most of the year.

Rainfall during the year was similar to the long-term rainfall pattern in which the majority of the rainfall occurred during the typically wetter months of July–September and May–June (Figure C3). Rainfall was above average during three of these months: August–September 2013 and May 2014. Very little rainfall occurred across the region during the summer period.

 

Figure C3 Graph of total monthly rainfall for the Perth region during the 2013–14 year compared with the long-term average and percentiles for the region
Figure C3 Total monthly rainfall for the Perth region during the 2013–14 year compared with the long-term average and percentiles for the region

 

Evapotranspiration

Potential evapotranspiration across the Perth region was generally above average to very much above average for the 2013–14 year (Figure C4). 

 

Figure C4 Annual evapotranspiration deciles for the Perth region during the 2013–14 year
Figure C4 Annual evapotranspiration deciles for the Perth 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 Perth region during the 2013–14 year was 1,258 mm, which is above the long-term area-averaged potential evapotranspiration of 1,216 mm (based on the 1970–2014 period). Potential evapotranspiration was highest along the Darling escarpment ridge in the central to southern part of the region and lowest in the southeast (Figure C5).

 

Figure C5 Total annual potential evapotranspiration for the Perth region during the 2013–14 year
Figure C5 Total annual potential evapotranspiration for the Perth region during the 2013–14 year

 

Temperature

During the 2013–14 year, the entire Perth region experienced mean temperatures that were very much above the long-term average, based on the 1911–2014 period (Figure C6). This is similar to what has been observed in the region over the last few years.

 

Figure C6 Annual mean temperature deciles for the Perth region during the 2013–14 year
Figure C6 Annual mean temperature deciles for the Perth region during the 2013–14 year

 

Annual mean temperatures across the entire Perth region were above 15°C. The western half of the region was warmer than the east (Figure C7).

 

Figure C7 Annual mean temperature for the Perth region during the 2013–14 year
Figure C7 Annual mean temperature for the Perth region during the 2013–14 year

 

Monthly mean temperatures for the Perth region were above the long-term average for most of the 2013–14 year (Figure C8). Monthly mean temperatures for two months of the year were well above the 90th percentile. August 2013 was the warmest August on record for the Perth region; November 2013 was the second warmest November on record.

 

Figure C8 Graph of monthly mean temperature for the Perth region during the 2013–14 year compared with the long-term average and percentiles for the region
Figure C8 Monthly mean temperature for the Perth region during the 2013–14 year compared with the long-term average and percentiles for the region