Atmosphere And Weather

Weather Effects of El Nino



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As the owners of a wholesale nursery in Oregon, we are always looking skyward to see what our gifts will be. Longer warmth into the fall and our growing season is extended. Early cold and it is stunted. Too much rain and the fields are too soggy to dig until late spring. Too little rain and the dirt is too hard to dig. This year, it looks like we're in luck as the official prediction is for neither El Nino nor La Nina. We are entering what is called an ENSO neutral year which basically means normal. ENSO means El Nino Southern Oscillation and it is near the southern hemisphere where an El Nino begins.




El Nino which occurs every 2 to 7 years happens when a natural series of current changes, winds, and storms occurs in the Pacific Ocean in the region around the equator. The ocean warms up a few degrees Celsius and the place on the equator where big thunderstorms normally occurs moves eastward. Winds usually blow strongly from east to west along the equator pushing more water into the western Pacific. Since the east loses some of its upper (sun-warmed) water to the west, it becomes colder as the west becomes warmer. However, in an El Nino situation, the equator winds are weaker and some of the warmer water from the west goes back into the eastern Pacific making it warmer. From there it becomes a vicious cycle. With warmer oceans, the winds become even weaker and the eastern waters become even warmer. El Nino grows.




An El Nino year in the U.S. brings a warmer than normal winter in the upper Midwest, Northeast, and Canada, and cooler, wetter weather to central and southern California, northwest Mexico, and the southwestern U.S. The Pacific may have increased coastal erosion due to stronger winds, but the Atlantic will spawn fewer hurricanes. Here in the Northwest, we get more fog but a warmer drier winter and an early spring. El Ninos in the U.S. give farmers and the weather people a lot to talk about; elsewhere in the world, the results can be devastating.




Along the coasts of Peru and Ecuador, warm and wet summers (their Dec-Feb) can cause major flooding along with loss of fishing as the nutrient-rich cold water of the Humboldt Current is replaced by warm water. Loss of fish species affects not only humans but birds which depend upon them for food. When birds aren't present, their droppings which sustain the fertilizer industry along the South American coast aren't either. All of these effects may become critical if El Nino persists into February, March, and April. During the 1972 El Nino, the world's largest fishery industry collapsed due to overfishing of Peruvian anchoveta. In 1982-83, both jack mackerel and anchoveta populations were reduced and scallops increased. Other species like hake, shrimp, and sardines moved to cooler waters. The red tides off the California coast may also be associated with El Nino.




El Nino years also cause dry conditions in Southeast Asia and Northern Australia which can provoke more brush fires and worsening haze. El Nino is a worldwide phenomenon and records of its effects reach far back in history. Some historians have suggested that the demise of the Moche and other pre-Columbian Peruvian cultures were the result of an especially strong El Nino. It has even been theorized that the French Revolution was caused partly by poor crop yields of 1788-89 in Europe caused by an El Nino.




El Nino, meaning, "the little boy or Christ Child," was so named because it occurs near Christmas. La Nina, "the little girl" is the cold phase of El Nino Southern Oscillation. La Nina usually follows an El Nino and meterologists say we are coming out of the La Nina which started in 2007. La Nina means drier weather for the Central Plains and wetter, colder weather for Northern California and the Northwest. Forecasts are generally good forward looking to 18 months but as we all know, sometimes there are surprises. For those of us who depend upon the land for our livelihood, the prediction of an Enso neutral year in 2009 is good news.

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