The southern oscillation index soi is a measure of the intensity or strength of the walker circulation. Year djf jfm fma mam amj mjj jja jas aso son ond ndj. The southern oscillation entails a largescale pressure seesaw, on a time scale of 210 years, and with dipoles over the eastern south pacific and the greater indonesianaustralasian region, but spanning the global tropics. The soi is one measure of the largescale fluctuations in air pressure occurring between the western and eastern tropical pacific i. Oceanatmosphere coupled anomaly in the tropical pacific. The southern oscillation is an eastwest balancing movement of air masses between the pacific and the indoaustralian areas. At intervals that vary from 2 to 10 yr seasurface temperatures and rainfall are unusually high and the tradewinds are unusually weak over the tropical pacific ocean. From december 1997, this image shows the change of sea surface temperature from normal. The soi measures the difference in surface air pressure between tahiti and darwin. Ke trenberth, national center for atmospheric research, boulder, co, usa a 20 elsevier inc. The complete table going back to djf 1950 can be found here. Any strong change in enso statistics will therefore have serious climatic and ecological consequences. Southern oscillation an overview sciencedirect topics. We analyzed fossil coral reconstructions of enso spanning the past 7000 years from the northern line islands, located in the center of action for enso.
The connection between earths oceans and atmosphere has a direct impact on the weather and climate conditions we experience. The pattern can shift back and forth irregularly every two to seven years, and each phase triggers predictable disruptions of temperature, precipitation, and winds. Southern oscillation index soi teleconnections national. The southern oscillation index soi is a standardized index based on the observed sea level pressure differences between tahiti and darwin, australia. Jan 07, 2016 southern oscillation, in oceanography and climatology, is a coherent interannual fluctuation of atmospheric pressure over the tropical indopacific region. Here we provide a synopsis of our current understanding of the spatiotemporal complexity of this important climate mode and its influence on the earth system. The low phase of the so can be defined by anomalously lowhigh surface pressure at.
Ensoneutral is favored for the northern hemisphere summer 2020 60% chance. Ocean dynamics alter seasurface temperature, changing the atmospheric heating. Most global climate models do simulate enso, although. The southern oscillation index used for the figure is a composite number derived from observations of air pressure at sea level for cape. Enso is the anomalous and recurring pattern of cold and warm patches of water periodically developing off the western coast of south america. Sir gilbert walker discovered the southern oscillation, or largescale changes in sea level pressure across indonesia and the tropical pacific.
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