When a drought occurs in Indonesia, there could be flooding later in Kenya. But what are the linkages between these two disasters?
The answer is a phenomenon discovered 10 years ago called Indian Ocean Dipole (IOD).
During normal conditions in the Indian Ocean, the sea surface temperature is warmer in the east and cooler in the west. When an Indian Ocean Dipole event occurs, the situation is reversed.
Cooling of the eastern part of the Indian Ocean results in less convection and less rain. Consequently, we see a longer drought in western Indonesia during the summer and fall.
Meanwhile, on the opposite side of the Indian Ocean, the abnormal warming results in enhanced cloud formation, more rain and serious flooding in eastern Africa. Current research has revealed that this IOD effect not only alters weather patterns in the surrounding region, but also influences the weather in Europe and East Asia.
When climate events collide
Sometimes, the Indian Ocean Dipole can occur together with El-Nino in the Pacific, causing extreme weather and disaster events. When this happened in 1997, there was serious drought and extensive forest fires in Indonesia and Malaysia.
The haze resulting from the fires spread for more than 3200 km, covering six southeast Asian countries, and causing serious health problems in the region. At the same time, giant red tides were triggered by the diople, leading to collapse of the marine ecosystem along a 400 km stretch of an archipelago in western Sumatra.
When the IOD and El-Nino combined again in 2006, the worst flooding in 50 years occured in the Horn of Africa, affecting 1.8 million people. The flooding was followed by outbreaks of cholera, malaria and Rift Valley Fever.
Understanding the dipole
Research on the diople effect is still at a preliminary stage. Scientists are investigating the mechanism, effects, and linkages with other phenomena. In 2006, Japanese scientists successfully predicted its occurrence in 2006 and 2007. This breakthrough brought a window of opportunity for the early detection and preparation for dealing with the extreme weather and disaster impacts attributed to the Indian Ocean Dipole.
In May of this year, the same Japanese scientists, as well as some other climate groups, predicted the IOD’s return in 2008.
Extreme weather, natural disasters and health problems during IOD in 2006.
“As far as we know, there is no such occasion in the past 100 years when we have had three consecutive positive IODs. The decadal change in the ocean’s condition, under global warming stress, is an underlying factor for such frequent occurrences of IOD. This is similar to the “perpetual IOD”, which could have occurred several thousand years ago,” explained Dr. Toshio Yamagata and Dr. Swadhin Behera of the Tokyo-based Frontier Research Centre for Global Change to The Hindu Business Line. “I hope regional people have enough time to prepare for possible impacts the event may have on local weather.”
In 2008, cooling in southern Java started much earlier than usual. In mid-June, the Indian Meteorological Department announced that monsoon rain hit India early for the first time in more than a century. Some scientists warned that the current condition in the Indian Ocean is suitable to trigger the IOD, and it might already be happening.
The extreme weather conditions and disasters associated with IOD are a serious concern for all people and governments in the region. They can exacerbate existing health, social, economic and food security problems.
Early Indian Ocean Dipole warning and disaster preparation are crucially needed for the countries that might be affected. It is essential that the relevant agencies in each country monitor the latest prediction results and actual observation in order to make the necessary decisions.
♦
For the latest predictions on Indian Ocean Dipole, please visit:
Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
For other related climate predictions, please visit
APEC Climate Centre
Australian Government, Bureau of Meteorology
European Centre for Medium-Range Weather Forecasts
International Research Institute for Climate and Society
National Oceanic and Atmosphere Administration
For more update on the IOD news and information, please visit the Marufish BLoG.
Acknowledgements:
Special thanks to Prof. Yamagata, Dr. Behera, Dr. Luo, Dr. Saji and Mr. Tripathy.
