Physiography Extent Various boundaries have been used to define particularly the northern but also the southern limits of the Atlantic Ocean. There are no universally accepted boundary conventions. In the north the situation is further complicated by the fact that the Arctic Ocean frequently is considered to be a dependent sea of the Atlantic. This is because the Arctic basin —which stretches from the Bering Strait across the North Pole to Spitsbergen and Greenland —resembles a semienclosed basin i.
The Walker circulation is seen at the surface as easterly trade winds which move water and air warmed by the sun towards the west. The western side of the equatorial Pacific is characterized by warm, wet low pressure weather as the collected moisture is dumped in the form of typhoons and thunderstorms.
The water and air are returned to the east.
Both are now much cooler, and the air is much drier. The Walker circulation is caused by the pressure gradient force that results from a high pressure system over the eastern Pacific Ocean, and a low pressure system over Indonesia.
The Walker circulations of the tropical Indian, Pacific, and Atlantic basins result in westerly surface winds in northern summer in the first basin and easterly winds in the second and third basins.
As a result, the temperature structure of the three oceans display dramatic asymmetries. The equatorial Pacific and Atlantic both have cool surface temperatures in northern summer in the east, while cooler surface temperatures prevail only in the western Indian Ocean.
Some of these changes are forced externally, such as the seasonal shift of the sun into the Northern Hemisphere in summer. Other changes appear to be the result of coupled ocean-atmosphere feedback in which, for example, easterly winds cause the sea surface temperature to fall in the east, enhancing the zonal heat contrast and hence intensifying easterly winds across the basin.
These anomalous easterlies induce more equatorial upwelling and raise the thermocline in the east, amplifying the initial cooling by the southerlies. This coupled ocean-atmosphere feedback was originally proposed by Bjerknes.
From an oceanographic point of view, the equatorial cold tongue is caused by easterly winds. Were the Earth climate symmetric about the equator, cross-equatorial wind would vanish, and the cold tongue would be much weaker and have a very different zonal structure than is observed today.
This also creates ocean upwelling off the coasts of Peru and Ecuador and brings nutrient-rich cold water to the surface, increasing fishing stocks. The most recent three-month average for the area is computed, and if the region is more than 0.
Equatorial winds gather warm water pool toward the west. Cold water upwells along South American coast. Warm water pool approaches the South American coast.
The absence of cold upwelling increases warming. Warm water is farther west than usual. Neutral phase[ edit ] Average equatorial Pacific temperatures If the temperature variation from climatology is within 0. Neutral conditions are the transition between warm and cold phases of ENSO. Ocean temperatures by definitiontropical precipitation, and wind patterns are near average conditions during this phase.
This component is an oscillation in surface air pressure between the tropical eastern and the western Pacific Ocean waters.
Low atmospheric pressure tends to occur over warm water and high pressure occurs over cold water, in part because of deep convection over the warm water.
Although the Southern Oscillation Index has a long station record going back to the s, its reliability is limited due to the presence of both Darwin and Tahiti well south of the Equator, resulting in the surface air pressure at both locations being less directly related to ENSO.
The western one is located over Indonesia and the eastern one is located over equatorial Pacific, close to the South American coast. Time increases from top to bottom in the figure, so contours that are oriented from upper-left to lower-right represent movement from west to east.
It is a large-scale coupling between atmospheric circulation and tropical deep convection. This overall circulation pattern manifests itself in various ways, most clearly as anomalous rainfall. The wet phase of enhanced convection and precipitation is followed by a dry phase where thunderstorm activity is suppressed.(thesubscriptLstandsforlowpass).Others[Tzipermanetal., ] have used this 12 month filter F on Nino index time series, but no name was given to this quantity.
a. Something that follows naturally from a particular action, operation, or course; a consequence or outcome. See Synonyms at effect. The Catholic Diocese of El Paso has learned that the Grand Jury has indicted Brother Edwin Gallagher, C.F.P and Brother Richard Fish, C.F.P.
for criminal misappropriation of funds allegedly committed while they were serving at St. Joseph elementary school in El Paso. Examine the phenomenon of El Niño and its impact on the environment.
Using social studies, language arts, and science, learners will develop a news story on past occurrences of El Nino, its global effect on weather patterns, predictions. El Niño Surface Oscillation 2. El Niño Southern Oscillation 3. El Niño Southern Ocean 4.
El Niño Surfing Organization (b) What does El Niño involve? 1. warmer water moves eastward along the equator 2. A slackening in the trade winds 3. A little South American boy making waves in a pool.
Environment Notes for UPSC IAS Civil Services Examination PDF and MS Word. Environment and ecology, Environment for General Studies 3 - GS 3.