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14: Equatorial Processes

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    Equatorial processes are at the center of our understanding the influence of the ocean on the atmosphere, and they dominate the interannual fluctuations in global weather patterns. The sun warms the vast expanses of the tropical Pacific and Indian ocean, evaporating water. When the water condenses as rain it releases so much heat that these areas are the primary engine driving the atmospheric circulation (figure \(\PageIndex{1}\)). Rainfall over extensive areas exceeds three meters per year (figure \(5.4.1\)), and some oceanic regions receive more than five meters of rain per year. To put the numbers in perspective, five meters of rain per year releases on average \(400 \ \text{W/m}^{2}\) of heat to the atmosphere. Equatorial currents modulate the air-sea interactions, especially through the phenomenon known as El Niño, with global consequences. I describe here first the basic equatorial processes, then the year-to-year variability of the processes and the influence of the variability on weather patterns.

    Average diabatic heating between 700 and 50 mb in the atmosphere during December, January and February of 1983–1989.
    Figure \(\PageIndex{1}\): Average diabatic heating between 700 and 50 mb in the atmosphere during December, January and February calculated from ECMWF data for 1983–1989. Most of the heating is due to the release of latent heat by rain. After Webster et al. (1992).

    • 14.1: Equatorial Processes
      Characterization of the tropical ocean, including equatorial surface currents and factors affecting surface temperature.
    • 14.2: Variable Equatorial Circulation: El Niño/La Niña
      History of different equatorial processes that have been described with the term El Niño. Theory of the process described as El Niño today, a disruption of the ocean-atmosphere system over the whole equatorial Pacific.
    • 14.3: El Niño Teleconnections
      Discussion of the teleconnections (statistically significant correlations between weather occurring at different parts of the Earth) associated with El Niño.
    • 14.4: Observing El Niño
      Discussion of instrument arrays used to observe El Niño.
    • 14.5: Forecasting El Niño
      Various models that have been used in efforts to predict El Niños, including atmospheric, oceanic, coupled, and statistical models. Comparing the quality of these forecasts.
    • 14.6: Important Concepts
      Summary of major concepts covered in this chapter.

    This page titled 14: Equatorial Processes is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Robert H. Stewart via source content that was edited to the style and standards of the LibreTexts platform.