Understanding the Atlantic Niño dynamics is a key to prevent its socioeconomic impact in regions that are especially vulnerable such as the Gulf of Guinea.
The climatic effects of El Niño have strong socioeconomic and environmental implications all over the planet. The heavy rains that occur approximately every four years in the eastern equatorial part of the Pacific Ocean are attributed to this meteorological phenomenon that causes an increase in sea surface temperature.
However, El Niño is not the only phenomenon that alters the atmosphere general circulation, causes changes in humidity and regulates the rainfall regime in tropical regions. Something similar happens with the Atlantic Niño –named like this for its similarity with El Niño-, that is characterized by the appearance of warm sea surface temperature anomalies in the eastern equatorial Atlantic.
When it attains its full strength, the phenomenon increases rainfall and the frequency of extreme flooding over the West African countries bordering the Gulf of Guinea and in northeastern South America. Thus, understanding the dynamics and variables involved in the Atlantic Niño is key to prevent its socioeconomic impact in regions that are especially vulnerable such as the Gulf of Guinea.
To better understand this phenomenon, experts have been monitoring the sea surface temperature anomalies during Atlantic Niño events. Thanks to this, they have realised that not all Atlantic Niño events are alike, since some appear earlier than others or persist longer.
Now, a group of researchers from the Institut de Ciències del Mar (ICM) of Barcelona have identified the four most frequently recurring Atlantic Niño varieties, which display remarkable differences in rainfall response over West Africa and South America depending on the intensity of the equatorial trade winds. The results of their research have now been published in the journal Geophysical Research Letters.
“To understand the rainfall regime in West Africa related to this phenomenon we need to know not only when the sea surface temperature is above the average, but also how it is distributed throughout the basin and what is its persistence in time”, explains Ignasi Vallès, one of the authors of the study.
Moreover, the expert details that for the analysis they have used data obtained from observations between 1948 and 2019. “In total, we have used data from three different data sources of sea surface temperature and we have obtained very similar results, which gives a greater robustness to the study”, celebrates Ignasi.
The results of this work, carried out in collaboration with NOAA's Atlantic Oceanographic and Meteorological Laboratory (NOAA-AOML), help improve predictions of climate models in the Tropical Atlantic and adjacent continents. Moreover, they show that the sea surface temperature in the Tropical Atlantic is increasing, but its variability is decreasing, which can affect Atlantic Niño events, and consequently, have a significant impact on the climate .