Geo-Final-Notes - Friday April 3 2015 Geo Final Notes Climate Classification and ENSO El Nio(ENSO El Nio Southern Oscillation El Nio and La Nia the term

Geo-Final-Notes - Friday April 3 2015 Geo Final Notes...

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Friday, April 3, 2015 Geo Final Notes Climate Classification and ENSO - El Niño (ENSO) El Niño Southern Oscillation - El Niño and La Niña the term El Niño means ‘Christ's child’ and was first used by Peruvian fisherman in the late 1800s to describe the warm current appearing off the western coast of Ecuador and Peru around christmas time El Niño describes the warm phase of a naturally occurring sea surface temperature oscillation in the the tropical pacific ocean La Niña describes the cold phase of a naturally occurring sea surface temperature oscillation in the tropical pacific ocean - ENSO shift in the interaction between the atmosphere and the ocean in the tropical pacific is the southern oscillation southern oscillation refers to a seesaw shift in surface air pressure at Darwin, Australia and the South Pacific Island of Tahiti. When the pressure is high at Darwin it is low at Tahiti and vice versa worldwide effects on temperature and precipitation strongest ENSO 1997-1998 and 1982-1983 - La Niña surface water temperature in the central and eastern pacific cool to below normal (x>0.5˚C) called La Niña - typical El Niño oceanic and atmospheric conditions include: deep layer of very warm ocean water across the was central equatorial pacific, with sea-surface temperature generally 1.5˚-2.5˚ C above average, and subsurface ocean temperatures typically 3˚-6˚ above average the depth of the oceanic thermocline a deeper than average oceanic thermocline across the east-central equatorial pacific, with depths typically ranging from 150-175M enhanced convective rainfall and below average air pressure across the eastern half of the equatorial pacific suppressed convective rain fall and above average air pressure across the western equatorial pacific and northern Australia weaker than average easterly trade winds across the eastern half of the equatorial pacific westerly winds at low levels of the atmosphere across the western equatorial pacific strong negative value of the southern oscillation index due to lower than average surface air pressure at Tahiti, French Polynesia and higher than average surface air pressure at Darwin Australia a weaker than average equatorial Walker Circulation 1
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Friday, April 3, 2015 changes in strength and position to the jet streams (over the eastern half of the pacific ocean) in both hemispheres in August-October increased upper level westerly winds lead to higher-than-average vertical wind shear and reduced hurricane activity across the tropical North Atlantic, and to below-average vertical wind shear and increased hurricane activity of the eastern tropical North Pacific - Southern Oscillation Index the cyclic warming and cooling of the eastern and central pacific leaves it’s distinctive fingerprint on sea level pressure when air pressure measured at Darwin is compared with pressure measured at Tahiti the difference between these two can be used to generate an “index” number a positive number indicates a La Niña (or ocean cooling), a negative
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