Mozambique and
Central Australia: Meteorologists blame La Nina Muddy brown waters and ensuing tragedy seemed to dominate the world news during the early quarter of 2000 and for good reason: wet season soakings were causing the worst floods in decades throughout the plains of Southern Africa and Central Australia. According to Dr Bill Wright of Australia's National Climate Centre in Melbourne, there is a broad-scale climate connection between the two countries and it is called La Nina. These weather events tend to build up and peak at the end of the calendar year, he says. Don't expect every La Nina to cause as much damage as this one, however. The La Nina in 1996, for example, caused little damage in Australia and merely caused the desert to bloom for a while. Why do Pacific events like El Nino Dr Wright explains that fluctuations in tropical Pacific rainfall patterns (associated with El Nino and La Nina) create changes in the normal atmospheric circulation patterns. These circulation changes can affect large areas of the globe for many months. "Tropical rainfall contain tremendous energy," he explains. "When it is redistributed, weather patterns are affected, leading to a complex change in events." The 'maritime continent' of south-east Asia, with its warm, shallow seas and high mountain ranges ensure there is a large area of moisture and rainfall. Dr Wright calls it the 'boiler box' of the earth's circulation. If something disrupts it, the change affects global weather. "It is no accident that El Nino-La Nina Southern Oscillation (ENSO) occurs over the Pacific," Dr Wright says. Wright points out that weather patterns are like 'teleconnections' in that they affect other weather patterns many thousands of kilometres away, often well away from the tropics or the Pacific. "For instance," he says, "El Nino is well known to result in unusually warm, dry conditions in the northwestern United States and western Canada, areas you wouldn't expect to be influenced by the tropics! Similarly, the Indian monsoon (and, of course, southeastern Africa including Mozambique) are also strongly influenced by El Nino and La Nina events in the tropical Pacific. As a matter of fact the 1991/92 El Nino caused 'the drought of the Century' in southeastern Africa, including southern Mozambique and Zimbabwe (but that's another story!)" © weather-wise.com 2000 |