Tic Toc, the ENSO clock, the origins of natural variability in climate.

reality

Let me introduce the actors in this play.

Chilean High 20-40S. Latitude, 240-290E Longitude. Maritime Continent 0-10S. Latitude, 120-180 Longitude. Aleutian Low 45-60N. Latitude 180-210 E Longitude. The blue line in the graph registers surface pressure in the region of the Aleutian Low. The orange line traces the difference in surface pressure between the Chilean High and the Maritime continent that is a name for the thousands of islands and the surrounding waters where low pressure prevails to the north of the Australian continent.

The difference in sea level pressure between Tahiti and Darwin is the basis of the Southern Oscillation Index. This is a good way of monitoring the movement of the centre of convection between Indonesia and the eastern Pacific Ocean. But this is really a local phenomenon that plays out along the equator. The bigger picture involves the atmospheric pressure differential that governs the rate of mixing…

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