Indo-Pacific Ocean warming is changing global rainfall patterns, say researchers

It’s ‘according to a new study’ time again, as the Madden-Julian Oscillation (MJO) goes under the microscope. Another causes and effects puzzle.

New research by NOAA and a visiting scientist from India shows that warming of the Indo-Pacific Ocean is altering rainfall patterns from the tropics to the United States, contributing to declines in rainfall on the United States west and east coasts, reports Phys.org.

In a study published this week in the journal Nature, researchers report a doubling in the size of a warm pool of water spanning the western Pacific and eastern Indian Ocean in recent years.

This Indo-Pacific warm pool in what is already the warmest part of the global ocean is expanding each year by an area the size of California.

The expansion is changing a key weather and climate feature called the Madden-Julian Oscillation, which is characterized by a band of rain clouds that move over the tropical ocean from the Seychelles off Africa toward India and into the Pacific Ocean, influencing everything from monsoons in India to heat waves and flooding in the United States.

Warming ocean driving change in key climate pattern

The changes in the behavior of the MJO have brought a decline in rainfall to the central Pacific, the west and east coasts of the United States, north India, east Africa and the Yangtze basin in China.

These same changes are causing an increase in rainfall over northern Australia, the Amazon basin, southwest Africa and Southeast Asia, researchers conclude.

“NOAA is part of coordinated international efforts to extend the range of accurate weather forecasts out to lead times of two to four weeks and the MJO is one of the most important keys to the success of this enterprise,” said Michael McPhaden, a senior scientist at NOAA’s Pacific Marine Environmental Lab and co-author of the study.

“Our research provides a critical benchmark for determining which computer models to trust for extended range weather forecasting, based on their ability to simulate the observed behavior of the MJO in changing the climate.”

Though the entire Indo-Pacific Ocean has warmed, the warmest waters are over the west Pacific, creating a temperature contrast that drives moisture from the Indian Ocean to the west, enhancing cloud formation. This has changed the life cycle of the MJO. The length of time these clouds linger over the Indian Ocean has shrunk by four days from an average of 19 to 15 days.

Over the west Pacific, the clouds now reside five more days. It is this change in the residence of MJO-driven clouds that is altering weather patterns around the globe, researchers found.

Full article here.
– – –