For one to understand the effects of El Nino (El Nino-Southern Oscillation) on the global weather, one has to know what it means in the first place. El Nino a.k.a. ENSO is defined as the following: a quasi-periodic climate pattern that occurs across the tropical Pacific Ocean with the estimate of intervals every five years. Usually, El Nino’s counterpart called La Nina usually follows afterward. La Nina is the opposite of El Nino in terms of effects. In regards to how El Nino affects weather, it all depends on what part of the world and the season. The continents greatly affected by El Nino are: North America, South America, Asia, and Australia. There are parts of Africa that are affected by El Nino. However, it is not certain on how Europe is affected. But, one case would be Great Britain in regards to the blizzard of 2010.
There are several factors which have to be considered in regards to El Nino affecting the weather. The first factor can be traced to is the Walker circulation or the “Walker cell.” It is a concept model of the air flow in the troposphere of the tropics which are the lines on the opposite sides of the equator (Tropic of Cancer for the North and Tropic of Capricorn for the South). The Walker cell is triggered from the pressure gradient force which is the product the east Pacific Ocean’s high pressure system. The catalyst for El Nino is a change in the Walker cell if the circulation or pressure weakens or reverses and goes the other way. If the Walker cell strengthens in circulation, La Nina is triggered.
The next factor would be the Kelvin waves which are waves in the ocean/atmosphere that serves as a balance to the planet’s Coriolis force (a deflection of moving objects). In regards to the equator, it serves as a guide. Near South America, the Kelvin waves cross over the Pacific toward South America. Thus, it creates a pool of warm water near the western part of South America. This plays a crucial factor to South America during El Nino.
Those factors create El Nino. In turn, those factors play an instrumental role of El Nino affecting the global weather pattern of the Pacific Ocean. How does El Nino affect the weather? The effects of El Nino differ from one location to another.
In terms of South America, the effects differ from one country to another. Due to the warm pool of water near South America by the Kelvin waves, the thunderstorms become stronger. Thus, the west coast of North America and South America experience more rainfall. Because the pool of warm water is near South America, it experiences the stronger end of it. That is not the only affect, it also reduces the upwelling of cold water during that time. During that time, it helps the fertilizer industry but hurts the fishing industry. In regards to fishing, certain catches increase while certain catches decrease.
Chile’s winters during that time have large rainfall. Certain countries will experience snowfall which is not common. In parts of the top of South America and in Central America, the weather becomes hotter and drier.
In the case of North America, in particularly the United States, it’s weather is affected due to the change in vector of the jet stream. In the northern part of the United States, the weather is drier and warmer for the most part. This is because, during El Nino, the jet stream travels across the southern half of the United States. In the southwest United States, expect more rainy weather as that area becomes wetter than normal. In the southeast United States, the weather is cooler than usual. During La Nina, Canada expects much colder weather due to the Polar Jet getting pushed further upward. El Nino can make some parts of the United States suffer a more frigid winter than normal.
Also, in the case of North America, El Nino has an effect on the Atlantic Ocean. It reduces the number of hurricanes formed. Hurricanes thrive on the warm ocean currents. This in part of the jet stream traveling across the southern half of the United States. Since the jet stream brings cooler air, it takes away the warm air that hurricanes need to feed upon. Cool air and/or a lack of warmth is poison to hurricanes.
In East Africa, the weather is drier than normal. In Australia, the weather gets hotter than normal thus creating brush fires. However, more research has to be conducted on how El Nino affects the weather in Europe and Russia.
Overall, El Nino has a mass but diverse effect on the global weather with prejudice towards the Pacific Ocean. The effect changes the direction of where the weather patterns circulates by reversing or redirecting their vectors.