The Consequences of Cold Events for Peru
Ing. Norma OrdinolaLaboratorio de Fisica
Universidad de Piura
Piura,Peru
nordinol@upiura.udep.edu.pe
Definition and Characteristics
In Peru, since 1983, El Niño has been associated with large ecological and socio-economic disasters, especially in its coastal areas. These impacts have been primarily associated with torrential floods in northern Peru and devastating droughts in the south, especially over the high Andes. The characteristics of La Niña are generally opposite to those of El Niño. During La Niña events the sea surface temperatures (SSTs) are colder than average in the central and eastern equatorial Pacific and the trade winds are stronger than normal. It is fair to state that La Niña, which can be represented by the positive phase of the Southern Oscillation, is not as well understood as El Niño, and that more attention has been given to El Niño events and their impacts than to La Niña.
Categories
Four categories of El Niño intensity have been identified: strong, moderate, weak and very weak. However, there are considerable differences within each of these categories. For example, while the 1972 and 1976 El Niño events evolved in a similar manner, the events in 1982-83 and 1997-98 developed in different ways. Until recently, El Niño researchers said that the 1982-83 event was a "Mega" Niño, with a probability of a recurrence taking place in a 200-400 year period. However, it was only 15 years later the world witnessed an even greater El Niño event, which was more intense and likely had a more severe global impact. This event can be truly called the El Niño of the century. Presently there are no such categories for intensity of La Niña and we are not sure what amount of sea surface temperature change is needed in order to produce a strong, moderate, weak, or very weak La Niña.
Predictability
Researchers thought that the atmosphere-ocean coupling events of El Niño and La Niña were predictable and that the large general circulation models could predict with reasonable accuracy the occurrences of these phenomena. However, models have reliability up to only 3 months. The Southern Oscillation is aperiodic and thus it is unpredictable. There are also some uncertainties about the intensity as well as the nature and magnitude of the impacts associated with these phenomena.
Societal Impacts
Societal impacts of both El Niño and La Niña are important. The ripple effect of these events cuts across several geographic and economic boundaries and affect virtually all socio-economic aspects of human activities in Peru. There are both winners and losers as well as direct and indirect impacts. Some of the sectors that are most affected are:
- Agricultural Impacts
La Niña effects are more pronounced during the Southern Hemisphere winter (July-August), when one can observe lower than average temperatures. For example, a few years with low temperatures (around 12 degrees Centigrade), and rice crops are badly affected. However, cotton production experiences an increase of 45% during cold event years. This actually took place in 1963, 1964 and 1996.
- Fishing Impacts
Higher yields and thus greater exports during cold events have had a positive influence on the fishing industry. For example, in 1996 the anchoveta and sardine catches increased with a corresponding increase in exports. Warm ocean temperatures are generally associated with a reduction of the catches of some species such as anchoveta.
- Health Impacts
La Niña greatly impacts the health sector because of the higher numbers of bronchial diseases and respiratory illnesses that occur, especially in central and southern Peru where the humidity is higher. Health problems also aggravate an already bad poverty and pollution situation, thereby augmenting human suffering.
- Climatic Impacts
La Niña is associated with severe drought conditions in coastal areas as well as decreased temperatures. During normal years there is a reasonable amount of rain in the mountainous areas of Peru, as a result of the easterly trade wind flow over the Andes. But there is no rainfall along the coastal regions, unlike the situation during El Niño years.
Why the Interest in La Niña?
El Niño events and their devastating effects across the globe have received considerable media attention. Therefore, it is only natural that the rest of the ENSO cycle including La Niña should also be examined and analysed for its characteristics and its consequences. These two extremes of the ENSO cycle events should be studied in an integrated and comprehensive manner. A piecemeal approach to the ENSO cycle with a focus on only one type of event (e.g., El Niño) should be avoided.