Without a troublesome pattern in the South Pacific, there is no influence to upset a normal summer pattern in the Southern Hemisphere. The winter warmth will surely be translated into summer heat. This will tend to provide a good base for the regular heat low, usually called the Barotse Low, to form early and drift gradually westward by the mid-summer. This area marks the regular base of operations for the ITCZ in southern Africa. Developing waves, after the Sahel pattern, drift westward and stagnate in the Etosha area.
The effect of the warm belt of water, offshore the West Coast, will be key. Increased warmth can bring, by insolation, even warmer waters offshore. A heat low coupling with such a favourable situation can foster a rainfall event that can last for some two to three weeks. Two such events, across January to March, will mean a wet year. The drift eastward, in tandem with a suitable cold front and upper trough, moves the rain area eastward across those areas on the eastern fringe of the previous wet zone, eventually to cross the southern subcontinent. The Congo Air factor means rains of intensity become widespread. The ready ability for Congo air to be brought southward, we have already witnessed twice during the usually unfavourable winter months. The heat low affords an attraction for the moist air circulating round the surface anticyclones to be advected inland towards the vortex: another favourable aspect.
But what about the persistent subtropical High-pressure belt? Surely, cells of this system will drift across the subcontinent some few times during the range of November through to April. The winter pattern has indicated a duration of weeks during the most favourable period (Cooler land/warmer seas). The summer season sees these cores following a more southerly track. The likelihood of our far north and northeast being consistently on the moist periphery of these cores provides a further optimistic note.
Excessive oceanic warmth can lead to two events: one very favourable for rain, the other unfavourable. The Benguela (El) Nino recurs approximately mid-decade. The cause or causes are improperly understood, but links with the Gulf of Guinea have been cited as a likely cause. Economically and ecologically, this event means turmoil and disaster. The rainfall benefits are usually plentiful. The last event peaked during February 1995. The Indian Ocean is a warm ocean by any standard. It hosts the tropical revolving storm known as a Cyclone. These storms usually develop around the Mauritius area and northward. Their tracks include the coastal waters of Madagascar and into the Mozambique Channel, on occasions.
Just occasionally, these storms make landfall and head up the Limpopo valley. They do bring considerable falls of rain to the areas in their path. But these storms are surrounded by ring of descending air (what goes up must come down syndrome) this means a zone of dry, rainless weather. People with longer memories may recall such names as Domoina and Imboia which made their dry mark during January and February 1984. The potential for these storms to drift inland as opposed to tracking southward down the Mozambique Channel is dependent upon the individual events. The Global Warming factor and its influence upon such potential is not known. A storm penetrating to the Makarikari area of Botswana will throttle active convection across northern and eastern Namibia comprehensively.
The ability to peer into the weather future is best measured in hours, rather than days. The time requirement really means months or even half a year. Much capable effort is being put into climatic forecasting. This provides percentage possibilities, across the summer month ranges, of monthly rainfall totals. In our type of climate, these efforts provide little of day-to-day practical value. When we with all our "press two buttons" capabilities have learnt to read nature and follow the preparatory signs of natural life preparing for the next season, we will be several worthy steps down the road of long-term, seasonal forecasting.
This outlook may sound very promising, or at least optimistic. The causes for this have been looked at. The dismal alternatives do not show up in the foreground. The likelihood of a dramatic, rapid turnaround of the state of the Pacific Ocean is not an event with any record. As on occasions in the past, it is an overall wait-and-see scenario.
John Olszewski
Windhoek
Thursday, October 20, 2005
Monday, October 17, 2005
Another Bird Link Found to Dinosaurs
Paleontologists working in northwestern Patagonia have unearthed the nearly complete skeleton of a small dinosaur whose bird-like appearance suggests that flight may have evolved twice -- not only in birds but also among the prehistoric raptors of the southern hemisphere.
The newly discovered fossil, of a rooster-sized carnivore known as a dromaeosaur, lived 95 million years ago and is the oldest raptor ever found in the southern continents. Its discovery may signal that dromaeosaurs are much older than previously thought.
"We're really just scratching the surface," said Peter Makovicky, dinosaur curator of Chicago's Field Museum and lead author of a report on the find published Wednesday in the journal Nature. "The evidence is that we have a distinct (dromaeosaurs) lineage -- the southern lineage."
Makovicky and a team of Argentine paleontologists led by Sebastian Apesteguia, of Argentina's Natural History Foundation, collected the fossil from a well-known site known as La Buitrera, "The Vulture's Nest," in Rio Negro province, about 700 miles southeast of Buenos Aires. The team named the new creature Buitreraptor gonzalezorum, after brothers Fabian and Jorge Gonzalez, who found the fossil.
Before Buitreraptor, a few teeth and other bone fragments were the only dromaeosaur remains known in the southern hemisphere. This scarcity contrasted sharply with the relatively abundant deposits in North America and Asia of such well known dromaeosaurs as velociraptor, Utahraptor and smaller species unearthed in China.
Paleontologists generally regard the northern raptors, especially the Chinese fossils, as part of the evolutionary lineage that produced modern birds. Archaeopteryx, regarded as the first true bird, is about 145 million years old, while the feathered raptors of Liaoning, China, are dated at 130 million years.
While Buitreraptor is considerably younger, its location deep in South America's southern cone suggests that dromaeosaurs generally may be 180 million years old, dating to the time when Earth's single land mass split into northern and southern pieces.
"To say dromaeosaurs are 180 million years old is not a stretch at all," said paleontologist Matthew Lamanna, of the Carnegie Museum of Natural History, in Pittsburgh. "You look at the fossil record and see Archaeopteryx is 150 million years old, so dromaeosaurs should already be around."
Makovicky noted, however, that, unlike northern dromaeosaurs, Buitreraptor has a long, heron-like skull and teeth without serrated edges, like a steak knife. "These are unusual features, and we think we have a predator of small prey," he said, possibly one that dined on small snakes prevalent in the region.
Lamanna said that the differences between the northern and southern species also come as no surprise. Once researchers established that dromaeosaurs were evolving on two separate super- continents, "the fact that they come to be different is what we would expect."
On the other hand, Makovicky said Buitreraptor is clearly a dromaeosaur, displaying many typical characteristics, including a spiked middle toe for gutting prey, heavy hind limbs for fast running, a long tail and powerful forelimbs -- but not powerful enough to fly.
Makovicky and the research team also noticed that Buitreraptor also shared characteristics with an unusual 65-million-year-old fossil from Madagascar known as Rahonavis -- thought to have been a primitive, long-tailed bird.
By Guy Gugliotta
The newly discovered fossil, of a rooster-sized carnivore known as a dromaeosaur, lived 95 million years ago and is the oldest raptor ever found in the southern continents. Its discovery may signal that dromaeosaurs are much older than previously thought.
"We're really just scratching the surface," said Peter Makovicky, dinosaur curator of Chicago's Field Museum and lead author of a report on the find published Wednesday in the journal Nature. "The evidence is that we have a distinct (dromaeosaurs) lineage -- the southern lineage."
Makovicky and a team of Argentine paleontologists led by Sebastian Apesteguia, of Argentina's Natural History Foundation, collected the fossil from a well-known site known as La Buitrera, "The Vulture's Nest," in Rio Negro province, about 700 miles southeast of Buenos Aires. The team named the new creature Buitreraptor gonzalezorum, after brothers Fabian and Jorge Gonzalez, who found the fossil.
Before Buitreraptor, a few teeth and other bone fragments were the only dromaeosaur remains known in the southern hemisphere. This scarcity contrasted sharply with the relatively abundant deposits in North America and Asia of such well known dromaeosaurs as velociraptor, Utahraptor and smaller species unearthed in China.
Paleontologists generally regard the northern raptors, especially the Chinese fossils, as part of the evolutionary lineage that produced modern birds. Archaeopteryx, regarded as the first true bird, is about 145 million years old, while the feathered raptors of Liaoning, China, are dated at 130 million years.
While Buitreraptor is considerably younger, its location deep in South America's southern cone suggests that dromaeosaurs generally may be 180 million years old, dating to the time when Earth's single land mass split into northern and southern pieces.
"To say dromaeosaurs are 180 million years old is not a stretch at all," said paleontologist Matthew Lamanna, of the Carnegie Museum of Natural History, in Pittsburgh. "You look at the fossil record and see Archaeopteryx is 150 million years old, so dromaeosaurs should already be around."
Makovicky noted, however, that, unlike northern dromaeosaurs, Buitreraptor has a long, heron-like skull and teeth without serrated edges, like a steak knife. "These are unusual features, and we think we have a predator of small prey," he said, possibly one that dined on small snakes prevalent in the region.
Lamanna said that the differences between the northern and southern species also come as no surprise. Once researchers established that dromaeosaurs were evolving on two separate super- continents, "the fact that they come to be different is what we would expect."
On the other hand, Makovicky said Buitreraptor is clearly a dromaeosaur, displaying many typical characteristics, including a spiked middle toe for gutting prey, heavy hind limbs for fast running, a long tail and powerful forelimbs -- but not powerful enough to fly.
Makovicky and the research team also noticed that Buitreraptor also shared characteristics with an unusual 65-million-year-old fossil from Madagascar known as Rahonavis -- thought to have been a primitive, long-tailed bird.
By Guy Gugliotta
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