The Asian monsoon is getting predictable

Robert Monroe at the UC San Diego News Center: For much of Asia, the pace of life is tuned to rhythms of monsoons. The summer rainy season is especially important for securing the water and food supplies for more than a billion people. Its variations can mean the difference between drought and flood. Now a Scripps Institution of Oceanography, UC San Diego-led study reports on a crucial connection that could drastically improve the ability of forecasters to reliably predict the monsoon a few months in advance.

Yu Kosaka and Shang-Ping Xie from Scripps and colleagues from NOAA found that a winter appearance of the climate phenomenon called El Niño in the Pacific Ocean can leave its mark on monsoon formation in the Indian Ocean a full six months later. In between is an atmospheric phenomenon called the Pacific-Japan pattern that provides the teleconnection between the two ocean basins and further poleward to East Asia.

“It has long been a mystery that climate anomalies in the region correlate better with El Niño in the preceding winter than with the one developing in the concurrent summer,” said Xie, a climate scientist and inaugural holder of the Scripps Roger Revelle Chair in Environmental Science. “The new paper shows that Indian Ocean temperature and atmospheric anomalies in the western Pacific are physically coupled, and their interactions amplify each other. We demonstrated that this new mode of coupled ocean-atmospheric anomalies is predictable a season ahead. Such predictions have tremendous benefits to society.”

... “The last sound El Niño makes is in the western Pacific Ocean,” Kosaka said, “because the positive feedback between the Indian Ocean and Pacific-Japan pattern we found amplifies climate anomalies in this region.” The last echoes of El Niño have devastating consequences to the region....

Researchers studied anomalies of observed (a) and modeled (c) Indian Ocean sea-surface temperatures as well as observed (b) and modeled (d) precipitation patterns to establish a link between El Niño and the Asian monsoon. Image by PNAS.