Monday, March 15, 2010

El Niño

In the Garden
By Catherine Dougherty
It has been over a decade since we have had such winter weather. After many years we have finally received enough moisture to take us out of the drought category and in spite of the damage across the map, the severe weather has been a blessing for many. Atlanta, Georgia was running out of water and with El Niño, the reservoir is full once again.

The term El Niño is used daily on the weather reports and is simply a pattern of unusually warm ocean temperatures in the Pacific. The opposite is La Niña, which characterized by unusually cold ocean temperatures. These fluctuations of the ocean atmosphere in the tropical Pacific are the cause of drastic weather changes around the globe so observations of conditions there are essential for the prediction of short term climate variations.

This warm water, first noted by a fisherman off the coast of South America, was considered a religious phenomenon since it arrived around Christmas and thus El Niño means ‘The Little Boy’ or ‘Christ Child’ in Spanish.

During El Niño the trade winds relax in the central and western Pacific and the result of lengthy scientific research indicates there is a sharp rise in sea surface temperature with weakening winds. Among the consequences of this warm water is an increase in rainfall across the southern tier of the United States. However the eastward displacement of the atmospheric heat source overlaying the warmest water results in changes of global circulation, which in turn forces changes in weather in regions far removed from the tropical Pacific. Rainfall follows the warm water eastward causing flooding in Peru and lack of normal rain causes drought in Indonesia and Australia.

A moderate El Niño competing with a strong North Atlantic and Artic Oscillation tends to produce more than the usual number of polar and Arctic air masses, which in turn are partly responsible for the cold, snowy season in the Northeast.

Notable El Niño’s occurred in1986-1987 and I can recall the roads washing that year with unprecedented rains. The one of 1991-1992 flooded barns and homes and made Caddo and Canadian Counties disaster zones. The El Niño of 1997-1998 was the strongest and resulted in substantial nationwide flooding. The arrival of these weather phenomenon can not be predicted with accuracy. Each time we think we know where a piece fits into the climate puzzle, another piece turns up that needs to fit in as well.