Earlier this year we told you that a La Niña event was starting to occur. A La Niña event is when the water is cool across the equatorial Pacific Ocean. An El Niño event is when the water is warm across the equatorial Pacific Ocean, and is the opposite of a La Niña. These two events are important because both the La Niña and El Niño can affect weather systems across the Pacific Rim and beyond. Both events are commonly called the El Niño/La Niña-Southern Oscillation, or ENSO.
In the image to the right, we can see where cool water (shown in blue), stretches across the equatorial region of the Pacific Ocean. Earlier this year it is not a uniform deep blue, and instead had pockets of warm water contained within it. Now the image shows a strong, uniform deep blue indicating a strong La Niña event.
La Niña’s cold water signal is strong in the top two images. The left image shows ocean surface temperatures on December 15, 2010, as measured by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) on NASA’s Aqua satellite. In December 2010, sea surface temperatures were colder than average across the equatorial Pacific.
Now if we just knew what all that cold water meant to the weather! Instead, we get incredible rain in southern California when it’s supposed to be drier than usual.