SOUTH AMERICA: LA NI[yen]A UNLEASHES ERRATIC DROUGHTS, FLOODS.

By Daniela Estrada / Tierramrica *

SANTIAGO, Chile, Mar. 13, 2008 (IPS/GIN) -- Meteorologists are still struggling to predict the local impacts of La Ni[currency]a, a cyclic climate phenomenon which has caused severe drought in Chile and catastrophic floods in Bolivia, Ecuador, Peru and Argentina.

The death toll has already reached about 100, and around 1 million people have been affected by recent floods and drought.

"La Ni[currency]a" and "El Ni[currency]o" are the extreme phases of the oceanic-atmospheric phenomenon known as "El Ni[currency]o-Southern Oscillation," which takes place in the equatorial region of the Pacific Ocean every two to seven years, affecting many regions around the world to varying degrees.

La Ni[currency]a is characterized by an atypical cooling of the surface waters of the ocean and an increase in the winds blowing east to west at the equator. The better-known El Ni[currency]o involves the opposite: warmer surface waters and weaker winds.

La Ni[currency]a tends to provoke intense rains in Colombia, Ecuador, the high plains of Bolivia and Peru and northwestern Argentina. It produces drought in Uruguay, southern Brazil, northeastern Argentina and central Chile.

According to Jorge Carrasco, chief of Chile's weather and climate department at the government's Meteorological Directorate, the current La Ni[currency]a episode began in May or June of 2007 and is expected to conclude between June and August of 2008, marking the beginning of a neutral period.

To predict the El Ni[currency]o-Southern Oscillation behavior, experts use historical data and dynamic and statistical climate models generated at centers in the United States, Europe and Asia, which have great computing capacity, Carrasco said.

The information generated by those centers is available to everyone over the Internet.

"Nearly all the countries [of South America] have quite broad knowledge of the rainfall patterns associated with the presence of El Ni[currency]o and La Ni[currency]a in their own territories, especially Peru, Ecuador and Colombia," the expert said.

Rosa Compagnucci, a professor of natural sciences at the University of Buenos Aires, added that "one must keep in mind that the interaction of the atmosphere with the ocean is not linear, and that means that one El Ni[currency]o or La Ni[currency]a event is never identical to another."

"Although we can predict in advance and with some certainty the occurrence of an event -- and in some cases even its potential intensity -- it is more difficult to predict its local impact," added the atmosphere and ocean expert.

The La Ni[currency]a occurrence now under way has been an atypical manifestation in Chile. Experts say there should have been heavier rainfall in the central region of Araucan a during the southern hemisphere summer months, but it never came. Across the country, 144 municipalities have declared agricultural emergencies due to the effects of the drought.

La Ni[currency]a also surprised meteorologists in Bolivia because instead of hitting the high plains -- in the western provinces of La Paz, Potos and Oruro -- it has affected the entire country, but especially Pando, in the north, and Beni and Santa Cruz in the east, which had already suffered heavy floods a year ago caused by rains from El Ni[currency]o.

Gualberto Carrasco, head of the climate unit at Bolivia's national weather and hydrology service, said: "This is the first time we've conducted a more exhaustive monitoring of La Ni[currency]a, because about the previous ones our information was quite general."

"In the short term it's important to strengthen the early warning system," said the expert from the weather and hydrology service -- known by its Spanish acronym, SENAMHI -- which is part of the Ministry of Sustainable Development and Planning.

Compagnucci added: "One of the difficulties Argentina faces is that the official forecasting agency, the National Meteorological Service, has dramatically reduced its scientific staff. If more meteorologists [were] trained, there would be greater awareness of these events of great socioeconomic impact."

Chilean expert Jorge Carrasco said the information produced by his country's Meteorological Directorate is presented to the relevant authorities on a regular basis, but he acknowledged that a greater effort could be made to provide basic information to the population about forecasts for droughts or floods to improve disaster prevention.

"There is sufficient information in terms of diagnosis and prediction [of the El Ni[currency]o-Southern Oscillation episodes]. The models are not 100 percent correct, but in general they have a good record three months out. As a result, there are data available for making decisions both at the governmental and personal levels," he said.

Meteorology professor at the University of Chile, Patricio Aceituno, added that "now under discussion is how to prepare programs" to adapt to and to mitigate climate change caused by human activities. "These programs should be inserted into permanent plans for mitigation and management of extreme climate situations, like drought and floods," he said.

"There is still great uncertainty about the changes that are going to occur in the next 50 years [due to global warming], but I would bet, with 100 percent certainty, that in the next 10 years there will be a major drought or flood," he said.

The Chilean experts point out that another phenomenon acts upon the El Ni[currency]o-Southern Oscillation, as well: the Pacific Decadal Oscillation, which manifests itself over decades and is believed to determine the frequency of La Ni[currency]a and El Ni[currency]o.

Studies indicate that the positive phase of the Pacific Decadal Oscillation, which has been taking place since the mid-1970s, is coming to an end. It is expected to begin its negative phase, in which La Ni[currency]a will become more frequent than El Ni[currency]o.

But other lines of research suggest that beginning in 2008, "when the new cycle begins of the approximately 11 years of solar activity, the probability of an El Ni[currency]o occurrence is on the rise, reaching maximum probability in 2012, the year -- according to predictions of NASA -- expected to have maximum solar activity," Compagnucci said.

(*With additional reporting by Marcela Valente in Argentina and Bernarda Claure in Bolivia. Originally published by Latin American newspapers that are part of the Tierramrica network. Tierramrica is a specialized news service produced by IPS with the backing of the United Nations Development Program and the United Nations Environment Program.)