Earth's most prominent rainfall feature creeping northward

Washington, July 2 (ANI): A new research has determined that the rain band near the equator that determines the supply of freshwater to nearly a billion people throughout the tropics and subtropics has been creeping north for more than 300 years, probably because of a warmer world.

If the band continues to migrate at just less than a mile (1.4 kilometers) a year, which is the average for all the years it has been moving north, then some Pacific islands near the equator - even those that currently enjoy abundant rainfall - may be drier within decades and starved of freshwater by mid-century or sooner.

The prospect of additional warming because of greenhouse gases means that situation could happen even sooner.

The findings suggest "that increasing greenhouse gases could potentially shift the primary band of precipitation in the tropics with profound implications for the societies and economies that depend on it."

"We're talking about the most prominent rainfall feature on the planet, one that many people depend on as the source of their freshwater because there is no groundwater to speak of where they live," said Julian Sachs, associate professor of oceanography at the University of Washington and lead author of the research paper.

"In addition many other people who live in the tropics but farther afield from the Pacific could be affected because this band of rain shapes atmospheric circulation patterns throughout the world," she added.

The band of rainfall happens at what is called the intertropical convergence zone.

There, just north of the equator, trade winds from the northern and southern hemispheres collide at the same time heat pours into the atmosphere from the tropical sun.

Rain clouds 30,000 feet thick in places proceed to dump as much as 13 feet (4 meters) of rain a year in some places.

The band stretching across the Pacific is generally between 3 degrees and 10 degrees north of the equator depending on the time of year. (ANI)