El nino and La nina phenomena explained

30 Dec, 2016 - 00:12 0 Views
El nino and La nina phenomena explained

The ManicaPost

Abraham Mudefi Enviromental Issues —
Greetings, I hope you are having a good rest this festive season. I had to take time from my break to pen off this episode of your favourite column on the environment.

This week I want to explain two weather phenomena that have great impact on our weather, agriculture, health and economy among other facets of our life. These concepts are the El Nino and the La Nina weather phenomena. We will understand why we sometimes have drought, severe flooding and sometimes just moderate weather conditions.

The El Nino and La Nino are some of the greatest weather phenomena that influences weather across the globe.

They are a natural force that can alter the atmospheric movement of trade winds to result in excess rain, drought, heat waves or extreme temperatures drops. The phenomena usually originate between the tropic of Capricorn and Tropic of cancer.

The energy required to power it is generated along the tropics. This usually extreme weather conditions is known as the El Nino Southern Oscillation (ENSO).

It is still a puzzle why these phenomena only originate between Australia and South America along the Pacific and not for example between Australia and Africa in the Indian Ocean or in the South Atlantic Ocean between Africa and South America.

Scientist uses data from ships, weather stations, ocean robots or satellite stations to determine the presence of the El Nino and La Nino phenomena.

When neither of these two phenomena does not seem evident the phase is called a neutral phase. A typical El Nino and La Nino takes between 6 to 12 months until weather patterns revert back to normal as is influenced by the trade winds, overhead sun and the local typographic conditions.

It also takes about 4 years for weather the phenomenon to swing between these two major phases. It is not really known what causes El Nino and La Nino.

Now for a closer examination of each of the two weather phenomena, starting with the El Nino weather concept.

The origins are not clearly known but some weather scientists believe that it was discovered by regular fishermen in the Tropical Pacific Ocean off coast of Australia.

They noted unusually cold currents near in the Australian Coast around Christmas time. In this coast upwelling Cold Ocean currents brought up ocean food and nutrients (Phosphorus and nitrates) to the Euphotic Zone.

This attracted lots of fish in the region due to excess food fueling the marine food web. During this time fish harvest declined the East Coast of South America due to the high temperatures that brought all food and nutrients further down to the ocean bed.

The cold water rises with ocean food and nutrients from the ocean bed that keeps fish and the marine life alive. So during an El Nino phase some regions have fewer fish than others depending on the ocean surface heating.

The El Nino weather phenomenon is not a storm but it is a complex phenomenon that is caused by unusually high Ocean Surface Temperatures. This occurs in the Eastern Tropical Pacific Ocean near the International Date Line off the Coast of South America.

This high temperature heat up the ocean surface resulting in high Ocean Surface Temperatures. Above the water warm air generates energy to alter the normal cycle of trade winds to a more local circulation called the Walker Circulation.

This happens between Australia and South America. The hot air generated in the coast of Australia (Western Pacific) is dumped in the Western Pacific, East coast of South America causing heavy rains in that region.

These warm trade winds causes the sea surface water to increase by 0.5 meters particularly across Indonesia as compared to Ecuador. The waters in Indonesia become relatively warmer by about 7.2 degrees Celsius compared to Ecuador.

This extra ordinary hot air currents carries a lot of moisture that is dumped in different parts of the world. As this happens other areas are starved of their normal seasonal rainfall leading to droughts.

Weather experts declare an El Nino when there is a distinct rise in temperatures in the East Pacific Ocean for a consecutive period of 3 months. There should also be an alteration of the atmospheric wind circulation movements (Trade Winds) and this has a consequent shift of rainfall patterns.

When this stream of warm air takes effect the normal West to East trade winds are weakened or reversed and moves towards the West. In recent years this concept has been recorded during the following years 1982 – 1983, 1997 – 1998, 2015 – 2016. The 1997 to 1998 is believed to be the most severe form of El Nino.

La Nina is the opposite of El Nino. The term has Spanish origins that mean “little Girl”. When there is no El Nino or La Nino the phase is called the Neutral Phase as stated before. The two weather phenomena, El Nino and La Nina take place after about 2 to 7 years.

It takes about 4 years for the oscillation from El Nino to la Nino to occur. The global winds are generally propelled by several factors that include where the sun is over head, the spinning of the earth, topographic variations and anthropogenic factors.

During a La Nina a reversal of the La Nino condition occur. It occurs when temperatures drop by between 3 to 5 Degrees Celsius in the East and Central Pacific Ocean close to the equator. The cool air usually occurs off the west coast of South America.

This interrupts the normal global trade winds when this occurs the movement of air from the west to the east does not bring with it the normal amount of moistures to effect a normal rainy season particularly for Southern Africa

The rapid drop or rise of Sea Surface Temperatures (SST) in the Tropical Pacific Ocean results in extreme weather conditions throughout the Globe. The increase in rainfall during the El Nino phase has resulted in flooding in most parts of the world.

This has led to deaths and destruction of property. In the 1997-1998 the El Nino phase killed many people and destroyed global property estimated at 8 Trillion dollars. El Nino also triggers tornadoes, cyclones and flooding. These high amounts of rainfall triggers water borne diseases like cholera and dysentery.

Other diseases vectors like malaria proliferate even in regions where they are unusually present. During the Lanina phase the cool air streams in the Eastern Pacific Ocean discourages the formation of rain in some regions across the globe particularly in regions East of the Pacific Ocean.

This triggers droughts due to the suppression of rain in the areas. Temperatures generally drop causing cold winters and summers with lower temperatures. These lower temperatures discourage rainfall in Southern Africa.

El Nina in Australia causes bush fires. The impact the two weather phenomena has a vast impact on the global business. Extreme weather generally discourages crop production resulting in crop failure. Many African countries depend on agriculture, drought and flooding robs communities of a livelihood.

The impact of El Nino and La Nina is greatest in poor developing countries. These countries have weaker Disaster Risk Reduction Strategies and their Response Network is weak. Such countries generally depend on donor countries to come to their aid when weather catastrophes strike.

The two weather phenomena cause scarcity of food and this drives the global and local market prices of food to astronomic levels. The impact in the North, Horn of Africa and Southern Africa is immense. In war torn and impoverished regions of Africa many people starve when such weather phenomenon occurs, worsening the difficulties already associated with War.

The EL Nino Southern Oscillation pattern is a definitive concept that is measured by the Sea Surface Temperatures between Tahiti French (Polynesia) and Australia (Port Darwin). This phenomenon can be predicted. Economists, Farmers, Civil Protection Services and communities should be on high alert and heed the predictions of the El Nino and La Nina effect.

This consequently requires planning. Authorities should find means and ways of mitigating the impact of these phenomena, particularly on food security, property damages and lives of people.

With the continued warming of the earth surface (Global Warming) the impact of El Nino and La Nino are likely to be exacerbated. Measures should be taken in the construction industries, farming (irrigation) to ensure that our communities are better prepared for this raving weather concepts. Happy New Year.

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