Tropical rainfall is on the rise, NASA scientists have said. Using a 27-year-long global record of rainfall assembled by the international scientific community from satellite and ground based instruments, the scientists found that the rainiest years in the tropics between 1979 and 2005 were mainly since 2001, a private television reported.
The rainiest year was 2005, followed by 2004, 1998, 2003 and 2002 respectively, said lead author Guojun Gu, a research scientist at Goddard Space Flight Center in Greenbelt, Md, US. "When we look at the whole planet over almost three decades, the total amount of rain falling has changed very little. But in the tropics, where nearly two-thirds of all rain falls, there has been an increase of five percent," Gu said.
Gu said the rainfall increase was concentrated over tropical oceans, with a slight decline over land. He said a warming trend in Earth's atmosphere and surface temperatures would produce an accelerated recycling of water between land, sea and air.
Warmer temperatures would increase the evaporation of water from the ocean and land and allow air to hold more moisture. Eventually, clouds that produce rain and snow would form with increasing frequency, he said.
The researchers found that during the El Nio years, total tropical rainfall did not change significantly, but more rain fell over oceans than usual, while the two major volcanoes both reduced overall tropical rainfall by about five percent during the two years following each eruption.
The researchers said with these effects removed from the rainfall record, the long-term trend now appeared more clearly in both the rainfall data over land and over the ocean.
The next step toward firmly establishing this initial indication of a long-term tropical rainfall trend is to continue to lengthen and improve our data record.
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