Mechanism of generating two types of El Niño under modern climatic conditions
Abstract
The contribution of horizontal and vertical advection and nonlinear dynamic heating to the formation of positive sea surface temperature anomaly during two types of El Niño is evaluated from the analysis of the ocean upper mixed layer heat budget using the GLORYS2v4 reanalysis data. The oceanic processes responsible for the increasing temperature anomaly during canonical and Modoki El Niños were identified for the modern climatic conditions (1992–2015). It is demonstrated that during the development phase of both types of El Niño the vertical and horizontal advection results in the growth of the upper mixed layer heat budjet in the tropical parts of the Pacific. The vertical advection plays the key role in the formation of heat anomaly in the eastern tropical Pacific for both El Niños while the horizontal advection prevails in the central tropical Pacific. The difference between the mechanism of heat content anomaly formation for canonical and Modoki El Niño is due to the different intensity of temperature growth. Moderate El Niños are characterized by intensive heating in the central tropical Pacific caused by zonal and meridional advection. During strong El Niños the contribution of vertical advection increases, especially in the eastern Pacific. Nonlinear dynamic heating is not supportive of the positive temperature anomaly growth, even causing the anomaly decrease in some cases.
Keywords
canonical and Modoki El Niño,
El Niño generat ion mechanism,
heat budget of the upper mixed layer of ocean
Supporting agencies: The study was undertaken within the scientific research topic АААА-А16-116032810086-4 and finantially supported by the Russian Foundation for Basic Research (project no. 18-05-00767).
About the Authors
A. M. Osipov
Lomonosov Moscow State University
Russian Federation
Faculty of Geography, Department of Meteorology and Climatology, post-graduate student
Russian Federation
Faculty of Geography, Department of Meteorology and Climatology, post-graduate student
D. Yu. Gushchina
Lomonosov Moscow State University
Russian Federation
Faculty of Geography, Department of Meteorology and Climatology, Professor, D.Sc. in Geography
Russian Federation
Faculty of Geography, Department of Meteorology and Climatology, Professor, D.Sc. in Geography
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For citations:
Osipov A.M., Gushchina D.Yu. Mechanism of generating two types of El Niño under modern climatic conditions. Lomonosov Geography Journal. 2021;(1):128-135. (In Russ.)
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