El Ninosouthern Oscillation

An El Niño event is a period of anomalous climatic conditions, centred in the tropical Pacific, that occurs at intervals of 2-7 years. Tiie most obvious sign ihat an El Niño event is underway is (he appearance of unusually warm surface water off the coast of Ecuador and Peru. This generally occurs within a few months of Christmas, and the name El Niño - meaning the Christ Child or, literally. 'The Boy' - was originally the local name for a seasonal warm current that flows south along the coast of Peru, particularly from Christmas time onwards.

Interest in the phenomenon of El Nifo goes hack to the mid-19th century, hut it was the El Niño event of 1972-7.1 that stimulated large-scale research into climatic fluctuations, which began to be seen as a result of the interaction between atmosphere and ocean. At the time. 1972 was known as the year of climate anomalies' - (here were devastating droughts in Australia, India, Africa and the (then) Soviet Union. and excessive rainfall around the Mediterranean and along the Pacific coast of South America. In addition, a number of important fisheries had greatly reduced catches. The most catastrophic and long-term collapse was that of the Peruvian anchoveta fishery, where the situation was exacerbated by overfishing. The extent to which these events were directly related to the El Niño event was not clear, but confidence in the world's ability to feed itself was badly shaken. This concern initialed political support for the large-scale climate research programmes ihat now form a significant part of scientific effort world-w ide.

(a)

Figure 5.21 (a) Schematic map showing the positions of the Indonesian Low and the South Pacific High. (This map should be studied in conjunction with Figure 2.3, showing the global wind pattern.)

(t)) The zonal atmospheric circulation between the Indonesian Low and the South Pacific High.

cool dry air sinks warm moist air rises

Was this article helpful?

0 0

Post a comment