El Niño Southern Oscillation och dess atmosfäriska fjärrpåverkan.
Physical geographyGeomorphologyClimate changeGreenhouse warmingCirculation patternsPedologyCartographyClimatologyNaturgeografiGeomorfologiMarkläraKartografiKlimatologiEarth and Environmental Sciences
This paper is a literature study aiming to describe scientists newest theories andknowledge concerning the El Niño and Southern Oscillation. Firstly I have described the?normal? conditions with rising and sinking air in Hadley- and Walker-cells in theequatorial Pacific and from there moved on to explaining the reversed circulation patternsand higher sea surface temperatures (SST) leading to rising air and anomalousprecipitation in eastern Pacific constituting the El Niño phenomenon. My outermostinterest regarding El Niño has been the associated teleconnections, especially in nontropicalareas. I have described the El Niño effect on the Indian summer monsoon, ontropical cyclones and on storms and precipitation on higher latitudes. Recently there hasbeen great concern due to increasing strength and frequency of El Niño-events and apossible influence from the greenhouse warming. However scientists do point to the factthat the series of contracted El Niños during the first half of the 1990´s not being uniquein a historical aspect. As for the increasing strength of El Niños (i.e. especially those in1982, 1986 and 1997) together with major flooding and draft, scientists have found thatanomalies in the El Niño per se (i.e. the SST) is not enough to explain a worldwideresponse. Some of the shown consequences and ?teleconnections? are instead due tonormal climate noise.The El Niño have been found to affect higher latitudes especially during the northernwinter, partly due to more frequent westerly flows during this period. The area with thegreatest teleconnection anomalies is without a doubt the southeastern Asia, Indonesia andnorthern Australia where major drought occurs in strong El Niño years.Research and evidence associated with ENSO is to a very high degree based uponstatistics. A strong relationship is said to occur with a correlation coefficient of 0.3. Mypersonal feel to this is that some scientists overestimate the use of statistics in definingrelationships between different climatic phenomena. Also some scientists seem veryeager, not to say desperate, to find new teleconnections associated with El Niño, whenclearly the relationships are still quite vague and circulation patterns too complex to fullygrasp.