News agencies reported that 27 people and up to a billion animals have been killed in Australia’s bushfires and thousands subjected to repeat evacuations. The most affected New South Wales (NSW), the country’s most populated state, alone reported a loss of more than 2,000 homes and over 650 damaged.
Role of the Indian monsoon in the Australian fire:
An extended wet monsoon in India appears to be the reason for delayed monsoon, dryness, drought, and wildfires in Australia.
- The late withdrawal of Indian monsoons: The 2019 June-September monsoon in India started its withdrawal on October 9, against the normal date of September 1, making it the most delayed in recorded history.
- The strongest monsoon in recent years with a surplus of 10% in 2019 — both attributed in part due to the positive phase of the Indian Ocean Dipole (IOD).
- Natural causes such as lightning strikes in drought-affected forests.
- The timely arrival of the monsoon rains could have helped Australia contain the spread of the fires but its delay past the normal December-end timeline caused the fire to spread uncontrolled.
The interrelation between Indian and Australian monsoons:
- Across the equator, the progression of monsoon winds more or less corresponds to the natural occurrence of troughs and ridges in the same pressure field as seen on the weather map.
- Every trough is matched by a crest somewhere.
- Troughs represent areas of low pressure featuring ascending motion of air and its cooling, clouds, and rain while ridges mean the reverse: high pressure from descending motion of air, dryness, heat, no clouds or rain.
- A positive IOD that persisted longer than usual may have contributed to a delay in the transition of the monsoon trough from the Northern Hemisphere to the Southern Hemisphere and onset of the Australian monsoon.
The risk of additional fires remains high: Australia is only just entering its summer season which means temperatures will peak in January and February, fuelling the fire.
About Indian Ocean Dipole (IOD)
- Sustained changes in the difference between sea surface temperatures of the tropical western and eastern Indian Ocean are known as the Indian Ocean Dipole or IOD.
- The IOD has three phases: neutral, positive and negative.
- Events usually start around May or June, peak between August and October and then rapidly decay when the monsoon arrives in the southern hemisphere around the end of spring.
Neutral IOD phase
- Water from the Pacific flows between the islands of Indonesia, keeping seas to Australia's northwest warm.
- Temperatures are close to normal across the tropical Indian Ocean, and hence the neutral IOD results in little change to Australia's climate.
Positive IOD phase
- Westerly winds weaken along the equator allowing warm water to shift towards Africa. Changes in the winds also allow cool water to rise up from the deep ocean in the east.
- This sets up a temperature difference across the tropical Indian Ocean with cooler than normal water in the east and warmer than normal water in the west.
- This often results in less rainfall and higher than normal temperatures over parts of Australia during winter and spring.
Negative IOD phase
- Westerly winds intensify along the equator, allowing warmer waters to concentrate near Australia.
- This sets up a temperature difference across the tropical Indian Ocean, with warmer than normal water in the east and cooler than normal water in the west.
- A negative IOD typically results in above-average winter-spring rainfall over parts of southern Australia as the warmer waters off northwest Australia provide more available moisture to weather systems crossing the country.
Upwelling occurs when dense cool nutrient-rich water from the bottom of the water column offshore replaces the nutrient-depleted surface water in the nearshore. It is driven by wind, the Coriolis effect and Ekman transport.
Downwelling occurs when surface water becomes denser and sinks to the bottom of the lake. It is driven by wind, the Coriolis effect, and Ekman transport.
Is the fire due to climate change?- Several climate change naysayers including US President Donald Trump have refuted climate change theory behind the fire.
Climate change responsible: In recent years, Australia has experienced longer dry conditions and exceptionally low rainfall.
Strong IOD responsible: It has coincided with one of the strongest IOD events ever on record.
Arson not responsible: Australian Police have clarified that only 24 people are currently facing criminal charges for deliberately igniting fires and even fewer have actually managed to start large fires.
Arson responsible: There are allegations that a big wave of arson may have fuelled the raging bushfires with U.S. President Donald Trump leading in the front.
Mindless politicization of climate change is responsible for a lot of misinformation.
Strong winds have also made the fires and smoke spread more rapidly, and have led to fatalities.
Weather conditions are growing more extreme, and for years, the fires have been starting earlier in the season and spreading with greater intensity.
Natural reasons: Dry lightning was responsible for starting a number of fires.
Worst droughts: Australia is also experiencing one of its worst droughts in decades.
Meanwhile, a heatwave in December broke the record for the highest nationwide average temperature.
Usual fire season: The fire season in Australia is always dangerous.
Also read: One-Fifth Of India’s Forests Prone To Fire