Worst La Nina in 40 years

SEVERAL countries in the Southern Hemisphere experienced their worst floods in decades in the past two months. While intense rainfall for over a month kept parts of Australia inundated for weeks, severe floods and landslides killed hundreds of people in Brazil and Sri Lanka, and affected more than one million. Countries like the Philippines and South Africa also experienced unusual rainfall.

Is there a link between these extreme rainfalls in the Southern Hemisphere? Scientists say the region is experiencing the most intense La Nina in the past four decades. It is a cyclical weather phenomenon that occurs every three to five years when the cooler-than-normal surface waters in the eastern and central Pacific Ocean result in heavy rainfall and storms on continental landmasses.

Peter Grace, global change professor at Queensland University of Technology in Brisbane, said global warming has exacerbated the usual La Nina phenomenon. La Nina intensified the Pacific trade winds and brought heavy rainfall and tropical cyclone Tasha to Australia, according to the country’s Bureau of Meteorology. “La Nina is still very strong and we expect more rainfall in coming months,” Harvey Stern, climatologist at the Met bureau, said. “It will be the wettest summer ever on the east coast.” Tasha inundated one-third of the eastern state Queensland, stranding 200,000 people.

Ajit Tyagi, Director General of the Indian Meteorological Department, New Delhi, said while the floods in Australia are a result of La Nina, Sri Lanka and Brazil are experiencing rainfall and mudslides because of monsoon season. But La Nina might have triggered their intensity, Tyagi added.

In Sri Lanka, the torrential rains were a fallout of the easterly trade winds crossing paths with the north-easterly monsoon winds, aiding the storms. According to the UN Office of Humanitarian Affairs, floods and mudslides caused by the heavy rainfall have affected nearly a million people in the country and displaced more than 127,000. Batticaloa district in the east received the highest rainfall in a century. The temperature in Colombo dropped to 18.8^oC on January 12, the lowest in more than 60 years.

Brazilian scientists have also claimed La Nina played a part in the heavy rainfalls that caused the worst natural disaster in five decades. Unprecedented storms hit the country on January 11-12, leading to mudslides and killing over 700 people. Maximum damage was caused in Rio de Janeiro, the country’s second largest city.

—DTE team

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