El Niño and La Niña

the changes in pressure we see between the Eastern and Western Pacific oceans in different years.

In a La Niña year, the Walker circulation is actually much stronger. This results in cooler temperatures in the eastern Pacific. The impact of a La Niña year is that there is a drop in surface temperature in areas of Southeast Asia. This means there are more heavy rains in areas like the Philippines, Indonesia, and Malaysia. Much further north in Alaska, a La Niña year means drier conditions.

In terms of storm tracks, the storm track will be southerly in an El Niño year. This means more rain in Southern California. The storm track moves more northward in a La Niña year, resulting in more rain in the Pacific Northwest. In the Midwest, a La Niña year means more snow in those areas along with hotter and drier summers. In the Gulf states, El Niño translates to more precipitation. In Hawaii El Niño means there will be a dry season. So, you can see that these southern oscillations can lead to wide differences in the temperature and precipitation from year-to-year in all parts of the Pacific and in the United States itself.

In recent years, meteorologists have recorded far more El Niño events and fewer La Niña events. While there are not enough years to make a decent prediction about this, it is expected this phenomenon will increase further as a result of global warming. In addition to the frequency of the El Niño events, it has also been observed at the amplitude if the variability is also increased. You can expect than that the difference between an El Niño year and a La Niña year will be greater as global warming worsens.

EL NIÑO AND LA NIÑA

While it is believed that phenomena like La Niña and El Niño have existed for a very long time, meteorologist not record these until fairly recently. They noted that there was a recurring cycle resulting in weather extremes that fluctuated from dry conditions to very wet conditions in any given area that would be affected by the Pacific Ocean. The Pacific Ocean is one of the main drivers of weather in the United States because weather comes from the West in general. As you can see, weather affects everything from the

amount of fish gotten in Peru to the number of storms you see in the Gulf states. Figure 33 more clearly shows how a normal year compares to an El Niño year:

Figure 33.

While La Niña years have been present as long as El Niño years, we understand less about them. Because these are also extreme weather conditions, La Niña years and have devastating outcomes in different parts of the world. As you can imagine, the trade winds are very strong and the surface waters near the equator are colder. There is more bad weather in La Niña years, including more tornadoes and other cold weather conditions in the Midwest and in other parts of the world.