apa itu EL NINO?

chiKenliTeL

Understanding El Ni駉


Everybody wants to know what the weather is going to do each day -- and with good reason, considering the many destructive storms and tornadoes that have hit the U.S. recently. In 1997-1998, the weather effect known as El Ni駉 has been a favorite topic of conversation, as it seems to have caused most of those weather woes. But just what is El Ni駉? It's a periodic disruption of the Pacific's climatic system.

Many places received extra rain in 1998.     


Usually, trade winds blow west across the Pacific, causing warmer ocean waters to "pile up" in the west: near Indonesia, the sea's surface is actually about a foot and a half higher than it is near Ecuador. However, on a cyclical basis, the trade winds die down, disrupting this normal pattern. The warmer waters stay east, raising the water temperature, rather than migrating west. This changes atmospheric circulation and weather patterns around the globe -- what we call El Ni駉.

This El Ni駉 has had some notable effects. Rainfall in southeast Asia was far below normal in 1997-1998, while rainfall along the Pacific coast of South America was much higher than normal. North America, Europe, and east Asia saw higher than normal temperatures. California was hard hit by El Ni駉 storms. Elsewhere in the world, dry conditions fostered severe forest fires and ongoing haze conditions.

In Peru, one of the hardest-hit areas, torrential rains have triggered floods and mudslides, washing away homes, farms, bridges, and highways. Floods have even uprooted a cemetery in Trujillo, sending coffins floating down the street.

Marine mammals from whales to otters have been especially battered. They survive on prey that breeds in cool, nutrient-rich waters, and the changes in water temperatures have made it difficult for them to find food. In Peru, 180,000 sea lions once lived along the coast, but just 30,000 now remain. The rest have died or migrated in search of food.

On average, El Ni駉 occurs every two to seven years. This El Ni駉 is expected to last through May, with normal conditions returning this summer. The term "El Ni駉," which refers to the Christ child, was given to this weather pattern by Peruvian fishermen who noticed that warm currents arrived one year at Christmastime.

guynextdoor

el nino... mmgpp.. then apa itu la nina plak? no pairs no credits... huhu

chiKenliTeL

Between 1997 and 1998 the damage caused by the El Ni駉 Southern Oscillation was catastrophic for many parts of the world, but is there another threat that causes headlines around the world as scientists learn more about 'La Ni馻' (or cold episode southern oscillation)? What is this phenomena?

La Ni馻 translates from the Spanish as "The Child Girl" and meteorologically is the opposite of the more well known El Ni駉. The term La Ni馻 refers to the extensive cooling of the central and eastern Pacific. The subsequent changes to the atmosphere and ocean circulation are as varied and diverse as those of the earlier El Ni駉 event.

Lower than normal temperatures across the central and eastern Pacific Ocean have important effects on the weather and in particular on rainfall amounts. Increased sea temperatures on the western side of the Pacific means that here the atmosphere has more energy and the frequency of heavy rain and thunderstorms is increased.

Places like north Australia, Papua New Guinea and Indonesia will have more cloud and more rain, (the opposite to the dry weather during El Ni駉 and the problem with smog and bush fires). The strong temperature contrast across the Pacific means the easterly trade winds will be enhanced for the Pacific Ocean.

La Ni馻 is preceded by the build up of cooler than normal subsurface water in the tropical Pacific. Wave action and easterly winds will pull this colder water to the surface off the coast of Peru and Ecuador and as the easterly trade winds strengthen the effect becomes stronger.

La Ni馻 does not always follow an El Ni駉 event but there is some correlation between a swing back to normal conditions and an initial weak La Ni馻 being set up.

Typically La Ni馻 will last for up to 12 months and will be a generally less damaging event than the stronger El Ni駉, that is not to say that the global impact will not be as diverse.

Globally La Ni馻, in very general terms, will mean that those parts of the world that normally experience dry weather will be drier and those with wet weather will be wetter. The Atlantic and Pacific hurricane activity will increase with La Ni馻 and the effects of severe droughts are likely in those already dry parts of the world.

Broadly speaking, the La Ni馻 event could give drier conditions in Central East Africa, SW USA, Northern Mexico, South America etc. Wetter conditions could be experienced in North/North East Australia, South Africa, Southern Asia (during the monsoon) and the northern half of South America, Central America and the Hawaiian Islands.

Whilst historically these are the effects of a La Ni馻 event, as we have seen with El Ni駉, nothing is certain and the global impact is still to be fully understood.

rudz

Originally posted by chiKenliTeL at 25-2-2007 10:54 PM

teman nak bagi satu soalan la...
berdasarkan imej kat atas... adalah jelas ianya adalah suhu pada permukaan lautan (SST)...so, soalan teman;
a) macamana depa ukur suhu tu... (teman tahu mmg ada buoy..but bil. terlalu sedikit & then kapal jugak buat observation but off course la skit sangat...)
b) suhu pada waktu malam dan siang adalah berbeza...so, suhu yg dipamerkan tu suhu waktu bila

DDT_pacak85

bagus thread ni ...

rudz

Originally posted by DDT_pacak85 at 2-3-2007 06:40 PM
bagus thread ni ...

teman pun rasa thread nie bagus...BUT mana pembuka thread nie ???

chiKenliTeL

allo ~~~saya di sini, bukan ac di sini

chiKenliTeL

more....



mtobin@ldeo.columbia.edu

Predictability of El Nino: Recent Developments
Francis P. A.牋

Thanks to燩rof. B. N. Goswami


CENTER FOR ATMOSPHERIC AND OCEANIC SCIENCE

Indian Institute of Science

Bangalore-12, India


Understanding牋El Nino:

Strong winds during La Nina pile up the warm water in the west, causing the thermocline to slope downwards to the west and exposing cold water to the surface in the east.

Relaxed winds during El Nino permit the warm water to flow back eastward so that the thermocline becomes more horizontal.

The trade wind fluctuations are both the cause and consequence of the sea surface temperature variations.

The ocean-atmosphere interactions permit a variety of natural modes of oscillation. The phenomena observed in the tropical Pacific presumably correspond to one of or some combination of those modes.

Despite these considerable observational and theoretical advances over the past few decades, many issues are still being debated, and each El Nino still brings surprises.牋

The prolonged persistence of warm conditions in the early 1990s was as unexpected as the exceptional intensity of El Nino in 1982 and again in 1997; nobody knew what to expect of El Nino in 2002.牋





How predictable is El Nino?
What are the reasons for the decadal modulation of El Nino,牋the apparent change in its

chiKenliTeL

A useful analogy for the Southern Oscillation牋is a slightly damped, swinging pendulum sustained by modest blows at random times. In the absence of noise, El Nino would be perfectly predictable because the Southern Oscillation would be perfectly periodic while its amplitude slowly attenuates.牋

Noise sustains the oscillation and makes it irregular.牋

The initial conditions do matter because they describe the phase of the Southern Oscillation and strongly influence the impact of random disturbances. For example, a burst of westerly winds when the oscillation enters its El Nino phase is very different from the impact of the same winds when the oscillation enters its La Nina phase.牋