Ocean temperature patterns in tropics and subtropics will change rainfall patterns

February 27th, 2010 - 5:36 pm ICT by ANI  

Washington, Feb 27 (ANI): A team of scientists has found that that ocean temperature patterns in the tropics and subtropics will change in ways that will lead to significant changes in rainfall patterns.

The research was carried out by a team of scientists headed by meteorologist Shang-Ping Xie at the University of Hawaii at Manoa’s International Pacific Research Center

Scientists have mostly assumed that the surfaces of Earth’s oceans will warm rather evenly in the tropics.

This assumption has led to “wetter-gets-wetter” and “drier-gets-drier” regional rainfall projections.

Xie’s team has gathered evidence that, although ocean surface temperatures can be expected to increase mostly everywhere by the middle of the century, the increase may differ by up to 1.5 degree Celsius depending upon the region.

“Compared to the mean projected rise of 1degree C, such differences are fairly large and can have a pronounced impact on tropical and subtropical climate by altering atmospheric heating patterns and therefore rainfall,” explained Xie.

“Our results broadly indicate that regions of peak sea surface temperature will get wetter, and those relatively cool will get drier,” he said.

Two patterns stand out.

First, the maximum temperature rise in the Pacific is along a broad band at the equator.

Already today the equatorial Pacific sets the rhythm of a global climate oscillation as shown by the world-wide impact of El Nino.

This broad band of peak temperature on the equator changes the atmospheric heating in the models.

By anchoring a rainband similar to that during an El Nino, it influences climate around the world through atmospheric teleconnections.

A second ocean warming pattern with major impact on rainfall noted by Xie and his colleagues occurs in the Indian Ocean and would affect the lives of billions of people.

Overlayed on Indian Ocean warming for part of the year is what scientists call the Indian Ocean Dipole that occasionally occurs today once every decade or so.

Thus, the models show that warming in the western Indian Ocean is amplified, reaching 1.5 degree C, while the eastern Indian Ocean it is dampened to around 0.5 degree C.

“Should this pattern come about, it can be expected to dramatically shift rainfall over eastern Africa, India, and Southeast Asia. Droughts could then beset Indonesia and Australia, whereas regions of India and regions of Africa bordering the Arabian Sea could get more rain than today,” said Xie. (ANI)

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