El Niño; What Is It and How Does It Affect the Global Climate.
If you happen to live anywhere bordering the eastern coast of the Equatorial (Tropical) Pacific Ocean (for example: California, Ecuador, Peru, etc.), chances are you have heard of the phenomenon known as El Niño. If you are inclined to winter sports such as skiing and snowboarding, as am I; you may know El Niño as the great bringer of rainfall to the west Americas, which to us mountain goers means plenty of snow on our beautiful mountain ranges; but what exactly is El Niño? And how in the world does this mysterious event of nature affect the Earth so drastically?
The term “El Niño” refers to a naturally occurring happening in the equatorial region of the Pacific Ocean characterized by warmer than normal waters (varying by +/- 0.5˚C). This event may occur every several years (anywhere from 2-7 years), usually near the end of the year mark, the warming most often beginning around December and carrying on into later months. After peaking, the waters tend to cool slowly through the winter and spring of the next year, allowing the effects to be felt globally for sometimes over a full year, although such long lasting effects in any one place are atypical. The effects of El Niño vary from region to region but are usually associated with strong rains in some areas and drought in others; I will go into more details of the effects later in the article. Now that I have described what “El Niño” represents, let’s discuss how it occurs and how it affects the global climate.
In order to understand how an El Niño season happens, it is important to first understand the normal atmospheric circulation within the Pacific region; Figure 1 shows an example of the normal conditions present in the Pacific. Easterly trade winds (winds from east to west) push warmer surface water in the western direction, causing pooling of warmer water on the western side of the Pacific. Due to this displacement of water from east to west, cooler, more nutrient-dense water from the deep ocean is upwelled on the western side of the Pacific. The pooled warm water on the west side of the Pacific cause the air to be warmer, inducing more condensation and precipitation in that area of the globe; the opposite being true for the east side of the Pacific, where colder water/air creates less tumultuous weather. The warm air in the west gradually moves toward the east as it cools and falls into the lower atmosphere, thus reinforcing the easterly winds and creating the normal cycle of atmospheric circulation.
Figure 1. Normal atmospheric conditions over Pacific Ocean.
During an El Niño season, however, irregular atmospheric conditions occur over the equatorial region of the Pacific Ocean. The strong easterly trade winds which provide the framework for normal atmospheric circulation are much weaker during this phenomenon. Therefore, the warm water which would normally pool on the west side of the Pacific becomes spread out amongst the central region. This changes the normal patterns of wet, unsettled weather from occurring in the west Pacific to being spread out on both sides of the Pacific evenly, relatively. This means less rainfall than normal for the west Pacific and more rainfall than normal in the east Pacific. Figure 2 shows the atmospheric circulation witnessed during an El Niño season.
Figure 2. Atmospheric conditions of Pacific Ocean during
The effects of El Niño can be felt worldwide. The most heavily affected areas being the East and West coasts of the Pacific Ocean. Most common consequences include increased rainfall across the south-western tier of the United States, Peru and other neighboring countries, drastically increasing the chances of flooding in those areas. As well as drought on the western side of the Pacific Ocean affecting areas such as Indonesia and Australia, sometimes associated with devastating brush fires in Australia and neighboring regions. The shift of water temperatures has negative effects on sea life in the eastern Pacific as well. Because less of the nutrient rich cold waters from the deep ocean are upwelled, fish have to migrate out of the area to find food, which severely affects the sea birds and mammals, such as seals and sea lions, making it much harder for them to fulfill their normal diets.
The National Oceanic and Atmospheric Administration (NOAA) operates a network of buoys throughout the tropical (equatorial) Pacific Ocean that measure temperature, as well as, ocean and wind currents. Collected data are analyzed by complex computer models designed to predict an El Niño season. However, even the most sophisticated technology we have today cannot predict the exact severity, duration, or impact of any particular El Niño.
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