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I just posted a piece on the IRI home page about the latest La Niña. The map I show here tells us where we in the world can expect shifts in rainfall due to La Niña. We also produced a set of three video interviews of IRI scientists Lisa Goddard, Brad Lyon, Dave Dewitt and Paul Block, who share their knowledge of the La Niña - El Niño phenomenom, aka ENSO.


La Niña and Rainfall. For high res PDF (3.2mb)

As of mid-January, moderate-to-strong La Niña conditions continue to exist in the tropical Pacific. Scientists at the International Research Institute for Climate and Society expect these to linger, potentially causing additional shifts in rainfall patterns across many parts of the world in months to come. These shifts, combined with socioeconomic conditions and other factors, can make some parts of the world more vulnerable to impacts. However, La Niña conditions do allow the IRI and other institutions to produce more accurate seasonal forecasts and help better predict extreme drought or rainfall in some parts of the world. This enhanced predictability could help societies improve preparedness, issue early warnings and reduce any potentially negative impacts from La Niña.

"Based on current observations and on predictions from models, we see at least a 90% chance that La Niña conditions will continue through March 2011," says IRI's chief forecaster, Tony Barnston.

The term La Niña refers to a period of cooler-than-average sea-surface temperatures in the eastern and central equatorial Pacific Ocean that occurs as part of natural climate variability. This situation is roughly the opposite of what happens during El Niño events, when waters in this region are warmer-than-normal (see our past story on El Niño). Both are part of a larger climate cycle known as the El Niño-Southern Oscillation, or ENSO. Because the Pacific is the largest ocean on the planet, any significant changes in average conditions there, such as those that occur during La Niña or El Niño, can have consequences for temperature, rainfall and vegetation in faraway places.


Climate scientists have found La Niña's signature in the widespread flooding that occurred in Pakistan last year, as well as flooding in West Africa, South Africa, and most recently in Queensland, Australia, where an area estimated to be the size of France and Germany combined was left underwater. Places such as Indonesia and northern South America have also been receiving above-normal rainfall. But La Niña probably isn't to blame for the recent flooding in southeastern Brazil, says Barnston. The more likely culprit there was a pocket of above-average sea-surface temperatures in the southwest Atlantic that promoted low atmospheric pressure and an increased tendency for heavy rainfall.

Read the whole piece here. The video interviews are on the same page....

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