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  • New model offers better forecast of Asian monsoon and storm season

[HANOI] Researchers have developed a more accurate model for predicting the amount of summer rainfall and number of tropical storms in East and South-East Asia.

The study, published last month (22 January) in Proceedings of the National Academy of Sciences, advances understanding of the East Asian summer monsoon, a weather system that affects agricultural production and the lives of billions of people across the continent.

Researchers say the model could "significantly improve" monsoon and rainfall predictions in the region, which could aid governments and disaster-management specialists.

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Bin Wang, a meteorology professor at the University of Hawaii, United States and the study's lead author, says the new model is roughly twice as accurate in predicting rainfall and tropical storms in the summer months over East Asia compared with similar models developed over the past 30 years.

 

According to Wang, the predictions will be more accurate in mainland South-East Asia than in inland China, where colder fronts mix with tropical weather systems and oceans regulate land temperatures to a lesser extent.

The study sampled data collected from 1979 to 2009 to analyse the 'Western Pacific Subtropical High' (WPSH), a circulation system centred in the Philippine Sea that leads to precipitation and storms in East and South-East Asia.

The WPSH is largely influenced by springtime sea surface temperature fluctuations in the Pacific and Indian Oceans. By measuring these influences, the model can predict weather patterns for a given year across a wide area stretching from 5 to 40 degrees north of latitude, and from 100 to 140 degrees east of longitude, according to Wang.

Researchers noted that when the WPSH pressure is strong in the summer, monsoon rainfall tends to be above average over East Asia, but fewer storms make landfall in the western North Pacific.

"They have made a breakthrough," says Kyung-Ja Ha, a professor at Pusan National University in South Korea. "I believe that their work will give some insightful ideas to other monsoon scientists, stakeholders and policymakers."

But she notes that the model will need to be updated to take into account the effects of climate change.

The UN's Intergovernmental Panel on Climate Change reports that natural and human-induced climate change will increase the frequency of heavy precipitation and the average severity of tropical cyclones during this century.

However, it also says that there is a 66 to 100 per cent chance that the number of tropical cyclones will either fall or stay constant.

This article has been produced by SciDev.Net's South-East Asia & Pacific desk.

References

Proceedings of the National Academy of Sciences doi:10.1073/pnas.1214626110 (2013)