The Climatological Effects of the Australian Bushfires
Janice Davila
Climatology – Spring 2020
Abstract: Starting in the spring of 2019 Australia had suffered from an abundance of bushfires that impacted over 46 million acres of land, (DISASTER, 2020) which will cost billions of dollars in recovery costs. Meteorologists have studied this phenomenon and have concluded that the overall cause was due to drier than normal conditions, warmer ocean waters (El Niño), PyroCb Clouds and warmer than average temperatures, which in turn created and continued to ignite the Australian bushfires.
1. Introduction: The Australian bushfires which began in August of 2019 can be traced back to several climatological abnormalities: drier than normal conditions, warmer ocean waters (El Niño), pyroCb clouds and warmer than average temperatures. With data from several sources including but not limited to the Australian government (Bureau of Meteorology), the Australian Building Codes Board, National Oceanic and Atmospheric Administration (NOAA) and the Center for Disaster Philanthropy (CDP), data was gathered regarding the areas most affected by the bushfires. The topography for Australia and past climate data was taken into consideration to help determine the meteorological aspects of why the bushfires may have started and continued to burn for months on end in Australia of during 2019-2020.
2. Background: Australia’s fire season typically starts in late January into early February when the summer season ends. However, in 2019 warmer/drier air began to move into the country earlier than anticipated and created the proper conditions for the season to start sooner than anticipated. According to CNBC, the bushfires in Australia had grown so massive that they began creating their own weather system. The fires had begun creating so much heat that the clouds would form smoke-infused thunderstorms (Cosgrove, 2020) called pyrocumulonimbus (pyroCb), making conditions extremely dangerous. When pyroCb clouds were present, new fires would spread and the potential for fire tornadoes increased making efforts to extinguish the fires extremely difficult.
On August 8, 2019, a team of atmospheric scientists from NASA’s Earth Observatory had witnessed the pyroCb clouds forming into the lower stratosphere from a satellite feed over Australia. However, five months later in January of 2020 a total of 20 additional pyroCb clouds had been captured over Victoria and New South Wales (Cosgrove, 2020) which were categorized as major. Whenever pyroCb clouds form, satellites detect the thunderheads rising above the columns of the wildfire smoke resulting from the fire having an abundance of heat and moisture in the atmosphere, which then creates thunderstorms (NASA Earth Observatory, 2019).
In a recent publication entitled Wildfires, pyroCb was said to be classified as cloudy pixels exhibiting a thermal infrared brightness with temperatures below an approximated homogeneous liquid-water freezing threshold (Peterson et al, 2018), which would then imply a high vertical cloud development near the tropopause. Mike Fromm, a meteorologist from the U.S Naval Research Laboratory, says that the weather phenomenon (pyroCb) has been continuing to aid the fires with an increase of lightning, and these storms then spark new fires (Cosgrove, 2020) adding months to the current harrowing situation.
3. Data and Methods: In July of 2019 Australia had been experiencing its second warmest month ever recorded in over 110 years (Bureau of Meteorology, January 2020). The country also experienced its driest year on record being 40% below its yearly rainfall rate of 277.63mm (Bureau of Meteorology, January 2020); however, New South Wales and Victoria were the areas of most concern. With trends continuing into August, temperatures exceeded the monthly average in the east, west and north of the country (Bureau of Meteorology, September 2019).
Another area of interest for many meteorologists to help predict and monitor events such as the bushfires in Australia is the inclination of an El Niño season using the El Niño Southern Oscillation (ENSO). The ENSO determined the warm phase of a recurring climate pattern across the tropical pacific that may shift back and forth irregularly every two to seven years (NOAA, 2014). When an El Niño occurs, it can trigger an unpredictable flux in temperature, precipitation and winds, having a global effect. Equatorial cloudiness is another inclination of ENSO where cloudiness increased near the dateline and negative outgoing longwave radiation (OLR) anomalies are manifested (Shein, n.d.). When equatorial cloudiness increases, chances are that more convective activity in the central and eastern equatorial pacific are happening with colder cloud tops emitting less infrared radiation into space (Shein, n.d.). Thus, the data line given from Mid Nov 2018-Mid Aug 2019 (Bureau of Meteorology, March 2020) show that there was an indication of an El Niño season during that time frame which resulted in Australia experiencing drier and warmer weather.
The strongest positive Indian Ocean Dipole (IOD) events ever recorded occurred in 2020, indicating an irregularity of sea surface temperature in which the western Indian ocean had become warmer (Positive) than the eastern part of the ocean (NOAA, 2020). Currently the IOD is sitting at an In-Active status and has been since August of 2019’ (Bureau of Meteorology, March 2020). Although, the Oceanic Niño Index (ONI) has shown an increase in the sea surface temperatures since December of 2019 of 0.5°C (NOAA, 2001) to present (March 2020 of 0.5°C) which could indicate an El Niño season soon approaching.
Smoke plumes have been used to help identify volcanic eruptions, fires and even pyroCb clouds; but according to the article entitled Wildfire, one is given the calculations for determining the average particle mass density (Mρ= ( βR/ε)) which in turn can determine the stratospheric smoke layer. β is the average of CALIOP (Satellite) Level 1 backscatter, R is an assumed particulate extinction-to-backscatter lidar ratio and ε is the particle mass extinction coefficient, with Mρ being dependent on the physical and optical properties of the smoke particles (Peterson et al, 2020). On January 6, 2020 NASA had measured the smoke plumes over Australia using the CALIPSO satellite and found they had been 9-12 miles above the surface just a few days after the most explosive fire activity in Australia. Within two weeks the plumes had risen 15.5 miles, making it the highest plume ever recorded by the CALIPSO satellite (EarthSky, 2020).
4. Discussion: Australia’s topography can be divided into five sections: The Western Plateau, the Central Plains, the Eastern Coastal Plains, the Eastern Highlands and Tasmania. The Western Plateau, which is mainly desert and plains, has sandy ridges and rocky regions which encompass most of the western half of the continent. The Central Plains consist mostly of drainage basins and is known as one of the largest areas in the world for its internal drainage. The Easter Coastal Plains runs along the eastern seaboard and is bordered by the dividing range in the west and south Pacific Ocean, along with the Tasman Sea. The Eastern Highlands consist of many complex hills, mountains, ranges, plateaus and plains. Tasmania is Australia’s largest inland which is located south of the eastern seaboard, is very mountainous and is a famous vacation spot due to its average summer temperatures of 23°C.
After determining the topography of the country, one can then start to break down the climate zones for which there are eight (Australian Building Codes board, 2015). The Western Plateau, as well as the Central Plains of Australia, has several zones (1,3-6) which include: high humid summers with warm winters, hot/dry summers with warm/cool winters, and a warm and mild temperate. The Eastern Highlands are a part of zones (1-4,6,7 and 8) and have high/humid summers and warm/mild winters, hot/dry summers with warm/cool winters and a mild/cool temperate, along with an alpine climate. The Tasman region is in zone 8 (Australian Building Codes board, 2015) which includes a cool temperate (moderate temperatures) and an alpine climate meaning the average weather for its region.
The highest concentration of Australia’s bush fires were seen in New South Wales and Victoria, which are located in zones 6-8, along with, Bamaga and Kalumburu, which were also affected in zone 1 (BBC NEWS, 2020). Australia has also had a history for severe bush fires. The number of acres damaged has increased significantly, as well as the number of deaths (in humans) has decreased tremendously since the Black Saturday occurrence in 2009’ which killed 173 people (BBC NEWS, 2020). The climate data for the country shows that the warm and dry weather prior to the spring/summer season may have influenced the bush fires, although after the wave of heavy rains that slowed in January of 2020 an additional period of warmer temperatures emerged giving no relief with drought and high winds escalating matters (DISASTER, 2020). Data has also shown that summers in Australia have grown by a month since modern recordkeeping in 1910, consequently leading to a warmer and dryer climate (Gramling, 2020).
5. Conclusion: The climatological effects of the Australian bush fires were catastrophic on numerous levels. During the eight-month period, 34 people were pronounced dead, over 46 million acres were destroyed and over 480 million animals were injured or killed as a result of the bush fires. In January of 2020, NASA’s Aura Satellite collected preliminary data suggesting that the fires injected more carbon monoxide into the stratosphere (in January) than any other event observed outside of the tropics in a fifteen-year time span (EarthSky, 2020). This means the 2019-2020 Australian bushfires had produced three times as much poisonous gas than the British Columbia fire in 2017 and the Australian fire in 2009 combined.
But thanks to satellites, radiosondes and ground based remote sensing, scientists can help predict and monitor fires that ravish places such as Australia. However, if conditions continue Australia may experience another year of warm/dry weather which could ignite fires earlier than expected.
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