|Abnormal temperature spikes can also lead to unpredictable results during the El Niño period, Dmitry Aleksandrov believes.
Photo credit: Ilya Safarov
Wind, humidity, temperature, ocean currents, and other parameters can lead to unpredictable El Niño results. It is a phenomenon in which the temperature of the upper Pacific Ocean rises and the near-surface waters shift eastward. The onset of El Niño affects precipitation, fisheries in Peru, Chile, Ecuador, and changes in the planet's climate. How external factors determine the behavior of atmospheric-oceanic processes in the Pacific region was calculated by UrFU physicists. They published a description of the features of the unusual phenomenon and its scenarios in the journal Physica D: Nonlinear Phenomena.
"We used the classic Vallis model, which describes El Niño. This is a simple model, it takes into account the temperature difference between the east and west coasts, the heat exchange between the Pacific Ocean and the atmosphere, and the speed of air masses movement. We also took into account external noise - parameters that also affect atmospheric and oceanic processes, such as pressure changes, humidity, wind gusts, and ocean currents," says Dmitry Aleksandrov, Head of the Ural Federal University's Laboratory of Multi-Scale Mathematical Modeling.
According to UrFU physicists' calculations, external factors have a serious influence on this phenomenon. For example, the stronger the wind, the greater the temperature amplitude. Moreover, this can throw the system out of balance and cause unpredictable weather conditions.
"Our calculations have shown that the higher the intensity of the noise, the more unpredictable the consequences, the stronger the disturbances, the more intense El Niño will be. Sometimes a slight push is needed for the system to get out of equilibrium: a change in humidity or ocean currents. With the help of the model, we have managed to show how the process will develop under the influence of one or another factor. That is, we have not predicted the time of El Niño appearance or what will be its consequences for the global climate, we have calculated possible scenarios of this phenomenon and showed that under some conditions there will be one version of events, and under a different set of parameters - another," adds the physicist.
On the one hand, scientists still cannot predict when El Niño will come again, but, on the other hand, they have learned to predict how El Niño will behave. This is important because El Niño affects the climate as much as climate change affects the phenomenon. While El Niño was once thought to affect only South America, scientists are now certain that the abnormally warm water surface is having an effect throughout much of the Pacific Ocean, up to the 180th meridian. Moreover, global weather changes are more noticeable during El Niño periods: large-scale changes in ocean temperature, precipitation, atmospheric circulation, and vertical air movement over the tropical Pacific Ocean.
The essence of the process is this: there is a continuous warm current that originates off the coast of Peru and extends to the archipelago southeast of the Asian continent. It is an elongated area of heated water, about the size of the United States. The heated water evaporates intensely and releases energy into the atmosphere. Clouds form over the heated ocean. Typically, trade winds (constant easterly winds in the tropical zone) move a layer of this warm water away from the U.S. coast toward Asia. Near Indonesia, the current stops, and monsoon rains fall on southern Asia. During El Niño, the current is warmer than usual near the equator, so the trade winds are weaker or not blowing at all. The heated water spreads out to the sides and flows back to the U.S. coast. An anomalous zone of convection emerges. Rain and hurricanes hit Central and South America.
"We assume that extreme El Niño phenomena may become more frequent in the future and contribute to climate change, just as climate change affects El Niño occurrences. That is why El Niño is the process that should be taken into account in global climate models, but this is not done yet, because nobody knows how to take into account such unpredictable and complicated phenomenon," says Dmitry Aleksandrov.
El Niño is a natural phenomenon characterized by an abnormal increase in surface water temperature in the central and eastern equatorial zones of the Pacific Ocean. During El Niño the usual pattern of atmospheric processes in the tropical zone is disturbed, which can cause extreme climatic effects all over the world. Usually on the Pacific coast of South America the temperature of the ocean surface varies in the range of 15-19 degrees Celsius. During the El Niño period, the temperature rises by 2-10 degrees Celsius. The anomaly lasts from 8-9 months to a year or more.
Such fluctuations occur with periods from 2 to 10 years and exist (according to geological and paleoclimatic studies) for at least 300 thousand years. There have been several active El Niño cycles in the last decades: 1957–58, 1965–66, 1972–73, 1982–83, 1986–87, 1991–1993, 1994–95, 1997–98 and 2015–16.
Source/Credit: Ural Federal University