U.S. Water News Online
LIMA, Peru -- Farmers in the high Andes Mountains may have
been able to predict El Nino for centuries by observing whether
nearly invisible clouds dimmed the light from a cluster of stars
called the Pleiades.
A tradition for potato farming handed down from one generation to
the next teaches that the brightness of stars in the constellation
during June roughly predicted the rainfall during the growing season
from October to May.
The brighter the stars, the more abundant the rain for a potato
crop highly vulnerable to drought. If poor rains are predicted,
villagers in the mountains of Peru and Bolivia delay planting for
Benjamin Orlove at the University of California at Davis and
co-workers reported in the journal Nature that modern
meteorology supports the farming tradition.
His study of satellite and weather data suggests that wispy cirrus
clouds high in the atmosphere are more prevalent during El Nino, a
warming of the Pacific Ocean that occurs roughly every two to seven
``What is remarkable is how detailed this cloud data is,'' Orlove
Orlove, who spent more than 31/2 years in the Peruvian Andes, said
the clouds obscure the dimmest five of the 11 main stars that form
the Pleiades. The dimmer stars are on the outer edges of the
constellation, so it appears to shrink when viewed with the naked
eye, he said.
The changes apparently only can be seen in the clear, dry air of
the high Andes, which have a unique weather pattern, Orlove said.
The farming tradition may extend back to the 15th century and the
Inca empire, said Alan Kolata, a University of Chicago anthropologist
who specializes in the Andes. He said the Incas, who unified the
central Andes tribes, had extensive astronomical knowledge even
though they lacked a written language.
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