Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 9. helmikuuta 2009 klo 15:15 (GMT)
Unprecedented heat, high winds, and years of record drought fanned weekend fires that claimed at least 200 lives in Australia's southeastern state of Victoria. It was Australia's deadliest natural disaster ever. The fires burnt 1200 square miles, an area 80% the size of Rhode Island. "Out there it has been hell on earth", Victorian Premier John Brumby said Saturday in a televised address. It is difficult to imagine more hellish fire conditions than those observed in Victoria state's capital, Melbourne, on Saturday (February 7). The temperature soared to 115.5°F (46.4°C), the hottest ever recorded in the city, besting the previous record of 114°F (45.6°C) set on January 13, 1939. Humidities as low as 4% and sustained north winds that reached 43 mph, gusting to 51 mph, accompanied the furnace-like heat. The dry winds were easily able to fan fires in the parched vegetation. Severe drought conditions reign in Southeast Australia, where some regions--including the city of Melbourne--have experienced their worst drought on record over the past eight years.
The previous worst-ever Australian fires were the 1939 Black Friday fires, which burned an area nearly four times the size of Rhode Island (5800 square miles), killing 71 people, and the February 1983 Ash Wednesday fires, which killed 75 people and burned 1800 square miles.
Figure 1. This image from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite shows multiple large fires (outlined in red) burning in Southeast Australia's Victoria state on February 7. Huge plumes of smoke spread southeast, driven by fierce winds. Image credit: NASA Earth Observatory.
World's hottest temperature so far south
The heat wave over Southeast Australia began on January 27. A slow-moving high pressure system over the Tasman Sea, combined with an intense tropical low off the northwest coast of Western Australia and an active monsoon, provided ideal conditions for hot, tropical air to move over the southern parts of Australia. The most exceptional heat in January occurred in northern and eastern Tasmania. The previous state record of 105°F (40.8°C), set at Hobart on 4 January 1976, was broken on 29 January when it reached 107°F (41.5°C) at Flinders Island Airport. This record only lasted one day, as Scamander, on the east coast, reached 108°F (42.2°C) on the 30th. Four other sites broke the previous Tasmanian record that day. Nearly half of the island of Tasmania had its hottest day on record on January 30, with many records broken by large margins, particularly in the north. Launceston Airport (39.9°C) broke its previous record by 2.6 degrees°C. This is the second-largest margin by which a record high maximum has been broken at any of the 103 locations in the long-term high-quality Australian temperature data set. The January 2009 event has now been responsible for seven of the eight highest temperatures on record in Tasmania.
After a slight drop in temperatures the first few days of February, extreme heat moved back into Southeast Australia on February 6-7. The hottest temperature ever recorded in Victoria state was measured at Hopetoun, in the northwest, which hit 120°F (48.8°C) on February 7. This bested the old record of 117°F (47.2°C) set at Mildura in January 1939. The new record at Hopetoun is also the hottest temperature in the world so far south. Most of Victoria recorded its hottest day on record on February 7, and fourteen stations exceeded the previous state record temperature.
The January-February 2009 heat wave has also been unusually long lasting. Both Adelaide and Melbourne set records for the most consecutive days above 43°C. Adelaide's temperatures were at this level on each of the four days 27-30 January, and Melbourne's for three days from 28-30 January, breaking the previous records of two at both locations.
Spectacular nocturnal heat burst
On the morning of January 29, an exceptional nocturnal heat event occurred in the northern suburbs of Adelaide around 3 a.m. Strong northwesterly winds mixed hot air aloft to the surface. At RAAF Edinburgh, the temperature rose to 107°F (41.7°C) at 3:04 am. Such an event appears to be without known precedent in southern Australia.
Figure 2. Maximum temperature anomalies for February 7, 2009. Most of the southeast Australia state of Victoria experienced the highest temperatures ever recorded, with temperatures up to 32°F (18°C) above average. The cooler temperatures in northeastern Australia are due to the remnants of Tropical Cyclone Ellie and persistent monsoon rains. Image credit: "The exceptional January-February 2009 heat wave in south-eastern Australia, Australian Government Bureau of Meteorology.
Climate Change and Australia
As to whether this heat wave is due to climate change, Mr. Perry Wiles, senior climatologist with the NSW office of the Bureau of Meteorology said, "Climate change is not only increasing average temperatures, but also the frequency and severity of extreme temperature events. While any one event cannot be attributed to climate change, this heat wave is certainly consistent with that expectation. In a warming world we can expect similar extreme events more often."
Average annual temperatures have increased by about 1.3°F (0.75°C) in Australia over the past century, which is also the what the global average increase in temperature has been. According the 2007 Intergovernmental Panel on Climate Change (IPCC) report, average temperatures in Australia are expected to rise by about 4.7°F (2.6°C) by the year 2100. Droughts are expected to become more severe and more frequent in the southeastern regions affected by this weekend's fires (Figure 3), though other portions of Australia are expected to see increases in rainfall. These sorts of regional precipitation predictions are in their infancy, and we currently have low confidence in them. However, continued increases in summertime temperatures are likely to bring more frequent heat waves like this weekend's to Southeast Australia over the coming century.
Figure 3. Average temperature and precipitation changes over Australia and New Zealand from the 21 climate models used to formulate the 2007 IPCC climate change report (A1B scenario). Annual mean and summertime (December-January-February) changes are plotted for the period 1980-1999 vs. 2080-2099. Image credit: 2007 IPCC report, section 11, "Regional Climate projections".
For more information
"The exceptional January-February 2009 heat wave in south-eastern Australia", Australian Government Bureau of Meteorology.
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