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Lookout for gales and waves

A group from Inpe studies the formation of cyclones in the South Atlantic andmaintains an on-line service of meteorological forecasts

From his meteorological laboratory at the National Institute for Space Research (Inpe), in São José dos Campos, 85 kilometers from the coast, the mathematician Dr. Valdir Innocentini helps to save ships and to avoid coastal tragedies. When he discovers that a cyclone is forming in the South Atlantic with the possibility of the generation and propagation of giant waves for the coastal regions, he calls radio and television broadcasters and newspapers on the Brazilian coast, in order to alert fishermen and sailors about the risk of going out to sea. At the same time, the data bank for the page of the naval meteorological forecast that Inpe maintains on the Internet is fed. The site: www.atlasul.inpe.br – with maps, graphs and texts that include wind speeds and waves heights. The data is updated daily and is available with forecasts for the coming three days in any part of the planet.

Available on the Internet since the 15th of February 2000, this meteorological service in real time was possible thanks to the System of Wave Forecasts that Dr. Innocentini and his team developed during the thematic project The Dynamics of the Cyclone Genesis in the South Atlantic , financed by FAPESP. The researches had the partnership of the Institute of Meteorological (IPM) of the São Paulo State University (Unesp) in Bauru and of the collaboration of the Institute of Sea Studies Admiral Paulo Moreira (IEAPM) of the Brazilian Navy, in Arraial do Cabo (RJ).

The work of the group has already helped the population of Rio de Janeiro to confront large tidal waters such as that of the 31st of May and of the 1st of June in 1999. On that occasion, Dr. Innocentini warned the Civil Defense two days ahead about the possible intensification of an extra tropical cyclone (formation of winds originating from the South or North Atlantic) close to the coast of the State of Rio de Janeiro, along with intense roughness of the sea. He recommended that people refrain from fishing and not even remain on the seafront to admire the waves.

“After our warnings, the fishing boats did not go out to sea. However, in that occasion in 1999 a ship sank and a tourist from São Paulo was carried away by the waves while admiring the tidal waves on the beach.”

“Alerting the authorities, the press and the updated page on the Internet that points to the places at risk, is only possible because the system, which is developed with the application of various mathematical models from satellites and buoys, can identify the tropical cyclones and extra tropical cyclones that occur in the whole of the Atlantic. Of these only the extra tropical cyclones get to Brazil and the system can forecast the evolution of these events for the following 72 hours.”

The cyclone – also called typhoon when it occurs in the Pacific Ocean, hurricane in the Caribbean and tropical cyclone in the Indian Ocean – is clearly visible on the images of the satellite. It is pushed along by converging winds close to the surface. They are intensive winds, more than 40 meters per second (m/s) or 144 kilometers per hour (km/h), and have a reduced area of action, (close to 400 kilometers in diameter). They need to have warm water in the ocean in order to develop. In general, they form in a small disturbance in the atmospheric pressure that happens along latitude of 10 degrees, in the very tropical zone, from east to west, and they hit their maximum force in the region of the Caribbean. They are characterized by an eye, the center of the storm which is free of cloud, and form trails (areas in which the wind acts with a certain spatial uniformity) which can reach an extension of 200 kilometers, with strong and intense winds that hit the Caribbean Sea, the Gulf of Mexico and Florida.

“The extra tropical cyclones in South America,” clarifies the researcher, “don’t intensify over the mainland as was initially thought, but over the ocean around latitude 35 to 45 degrees along the seaboard of Uruguay and of the Argentine. Normally they spring up in the Pacific, cross the Andes along with the cold fronts and when they reach the Atlantic they intensify, forming strong winds that generate trails of up to 5 kilometers in extension. Consequently, they transfer energy in the form of movement to the sea, creating waves that reach out towards the Brazilian coast, mainly between the months of April until October.” Although much less devastating than the extra tropical cyclones, the tropical cyclones are accompanied by winds over 15 meters per second, equivalent to 54 km/h, and they produce most of the waves that arrive on the beaches.”

Coupled cyclones
Dr. Innocentini relates that sometimes a tropical cyclone, in a weakening phase, is absorbed by another tropical cyclone that intensifies quickly. This was what happened between the 24th and the 26th of October 1999, with the tropical cyclone Irene. It began on the coast of Africa, crossed the Atlantic, passed over part of the Florida coast, continued up north and was close to New York, losing momentum. Then it joined forces with a extra tropical cyclone that was along the Canadian coast. After the coupling, a region with enormous trails was formed with speeds of up to 20 m/s (72 km/h).

The waves set out in a southerly direction in the Atlantic and arrived fiercely at the archipelago of Saint Peter and Saint Paul, the small group of Brazilian rocks located 950 kilometers to the northeast of the coast of Rio Grande do Norte, where the navy has had a scientific station since 1998. The two researchers who were on the Southeast island, where the station was installed, only survived because they went to the local lighthouse, the only safe point, but the waves destroyed the nestsof the birds and damaged part of the infrastructure of the station and the researchinstruments.

The phenomenon is rare. “It only happens once or twice a decade.” says the researcher. He and his team retraced the event with the application of a model for the generation and propagation of waves. Based on mathematical equations, formulated to quantify the physical processes that influence waves, the model combines various pieces of information, mainly those relating to surface winds, and calculates the evolution of the height of the waves at each point of the ocean.

Sea roughness
Although observation about the waves that reached the archipelago were lacking in order to confirm the model, the study – Waves on the North Coast of Brazil Generated by Hurricanes: the Case of 24th of October 1999, shows the waves being generated in the extreme north of the Atlantic, crossing the equator, propagating themselves on the Brazilian north coast and hitting the archipelago. From the results of the model, this extra tropical cyclone generated waves taller than 8 meters in open sea close to the Iberian Peninsula, the north coast of Africa and the Azores, which ended up arriving at Brazil. In spite of the forecasts of the site of Inpe, there are still shipwrecks and other disasters. For example, on the 14th of December of last year the researchers sent out an alert and on the 16th and 17th and in the following week there was intense sea roughness on the coasts of Santa Catarina, Paraná and São Paulo.

The result was that, on that weekend, a sailboat that left Angra dos Reis disappeared on Sunday 17th and was only found at night on the southern coast of Paraná with only one of its three crewmen. According to the report of the survivor, the sailboat was knocked over twice by very high waves that threw overboard the other crew members – considered to be experienced sailors. On the same weekend, at Ilhabela, a ship went down on the Ponta dos Castelhanos with 13 people, of whom 12 were saved, and in Rio de Janeiro 21 people were isolated on three islands and the rescue was done by helicopter as the sea was too rough.

A graduate in mathematics from USP where he took his masters in meteorology, Dr. Innocentini took his doctorate at the English university of Reading in 1986. In 1989, he began to work at Inpe and, and on visiting the Research Institute of the navy in Arraial do Cabo, was told by the technicians about the necessity of forecasting waves in the country. It was necessary to overcome considerable backwardness, which could be proved by the following passage on the Inpe web page at that time: “Although the forecasting of the agitation of the sea generated by the wind through objective techniques had initiated at the end of the 50s, the interest of Brazilian researchers for this question appears to have only been aroused at the end of the 80’s.”

The forecast was important for the Rio de Janeiro State coast, frequently hit by strong and unexpected tidal waters. It is commonplace for sailors to go out by boat to fish at some islands and when the tidal wave arrives, with very strong waves and winds, they can’t get back. For this reason even large boats of 30 to 50 feet (10 to 15 meters in length) sink. There are life losses and the navy is obliged to carry out rescues by helicopter. Besides the shipwrecks, Dr. Innocentini confirms that when the waves are very high, routine operations in the ports and on the oil rigs become difficult and there is a high risk of accidents.

An advanced model
The problems provoked by extra tropical cyclones happen mainly between Rio Grande do Sul and Espírito Santo, but, before the work of the Inpe team was completed, the maximum that was done was to study the sea. “The researchers of the Oceanographic Institute of the University of São Paulo (USP) collect data on Ilha Comprida for studies on the variation of the height of the sea and at the Polytechnic School of USP, in the capital , the engineers make projects that demonstrate the effects of the waves on various locations of the Brazilian coastline. However, nobody works with the forecasting of the waves generated by the action of the wind, in the time range between 1 and 30 seconds, which is the variation of time possible between the passage of two waves.”, states Dr. Innocentini.

That is the reason why, between 1992 and 1994, he worked on a similar research project but prior to the present and also financed by FAPESP. On this project he developed a numerical model of waves based on work published in international magazines, to foresee the maritime roughness provoked by wind. However, he had difficulties to estimate if the model worked well and if the forecasts could be trusted, because there was no data about the phenomena on the Brazilian coastline.

Later, the Italian oceanographer Dr. Luigi Cavaleri, a researcher with the Istituto Studio Dinamica Grandi Massa, of Venice in Italy, provided data collected in the Mediterranean Sea referring to a month of measurements of winds and waves. From that moment on, Dr. Innocentini and the researcher Dr. Ernesto dos Santos Caetano Neto, of IPM of Unesp in Bauru, created a model for forecasting waves for the Mediterranean.

In 1997, Dr. Innocentini began to coordinate the present thematic project and, with the resources obtained, could count on a team of five researchers as well as the work stations (powerful computers) of the latest generation connected to the Internet. This allowed the development of a more advanced numerical model, initially based on information from two North American organizations, the National Center for Environmental Prediction (NCEP) and the National Oceanic and Atmospheric Administration (Noaa). This was necessary because, to have a good forecast on any part of the Brazilian coastline, it was necessary to have data about all of the Atlantic Ocean, from Canada and Great Britain to the Falkland Islands, since the waves that arrive on the coast of Brazil are generated above latitude 40 degrees in the North Atlantic, and below 40 degrees in the South Atlantic, in spots close to the poles.

In 1998, the team concluded its own system of forecasting waves for the Atlantic, the Atmospheric Model of Limited Area (Maal in the Portuguese acronym) that covers the Brazilian coastline. The system works with equations of atmospheric movements, use data, such as atmospheric pressure, relative humidity etc., from various sources and anticipate all of the meteorological parameters, including the winds that blow 10 meters above the surface. With the winds forecast by the atmospheric model, it is possible to know the location of the generation, propagation, refraction, and dissipation of the waves for all of the Atlantic.

Nowadays, the researchers are already providing information about winds and waves that happen daily in the Atlantic and make forecasts with up to 72 hours in advance for all of the seaboard of Brazil, especially for the north coastline of São Paulo. The information is broadcast by TV Vanguarda, of the Paraíba valley, and is available on the Inpe site. In the future, Dr. Innocentini and the team intends toimplement a model of waves more adequatefor shallow seas (with less than 50 meters of depth), that should generate information ever more detailed about the propagation in the coastal regions, firstly of the São Paulo north coast and later on for all of the Brazilian coastline. A job that should contribute even more to avoiding accidents and to open new fields of use, such as to facilitate the anchoring of ships and even to help surfers to choose their beach.

The wave model is passed on to Peru

Since last year, the Peruvian navy has been able to count upon a forecast model of waves for all of the Pacific, implanted by Dr. Valdir Innocentini and based on technology developed by technicians at Inpe. The goal is to know in detail how cyclones occur in the Pacific and to have a forecast model of waves for the small Peruvian bays, says Fernando Vegas Castañeda, lieutenant at the Division of Hydrographic and Navigation of the Peruvian navy. He heads a mission of four people who arrived in Brazil on the 3rd of January last for six months of training at Inpe and at USP.

The Peruvians received our technology and managed to stay ahead of Brazil, comments Dr. Innocentini. The reason is that their forecast model of waves was inserted into the project Naylamp (El Niño Anual Y las Amostras Médias del Pacífico), a proposal to study the effect of the phenomenon a El Niño on the Peruvian coast with a US$ 5 million financing from the World Bank. This grant allowed the purchase of six well equipped buoys (two are for replacement) at the price tag of U$ 250,000 each and computer equipment for the implementation of numerical models of wave forecasting.

The four buoys in activity have sensors that measure the waves in detail, as well as diverse meteorological and oceanographic parameters. With this information, the Peruvian researchers intend to study and develop methods of forecasting the phenomenon El Niño, which periodically messes up the normal meteorological situation in the Pacific Ocean and causes disasters such as flooding and shipwrecks on the Peruvian coastline.

Vasco da Gama almost discovered Brazil

After studying the daily log of the expedition of Vasco da Gama who discovered the sea route to India, the team from Inpe managed, with their mathematical model, to rebuild the meteorological conditions of the voyage along the western coast of Africa, especially the storms confronted while going round Cape Hope (until that time called the Cape of Torments), both on the outgoing and incoming voyages.

The log of the Portuguese navigator, in part published in 1998 in the biography Vasco da Gama written by the Frenchwoman Geneviève Bouchon, has an intentional blank between the 22nd of August and the 27th of October of 1497, days consumed in the so called Large Loop: the ships got away from Africa and got close to the at that time officially unknown coast of Brazil. It was a military secret, the Spanish and others could not know of this route.

In the work Possible Difficulties that Accompanied the Voyage of Vasco da Gama to India, the team of Inpe explained that “the discovery of the route to India by the Portuguese navigators in the 15th century was the result of various unsuccessful expeditions into the Atlantic Ocean.” From these attempts the strategy of the Large Loop was devised, a maneuver in which the fleet sailed for the southwest after passing the Islands of Cape Verde. “Though this voyage was much longer, it was much quicker as the sails inflated more with the winds of the western sector of the subtropical anticyclone that pushed them to the extreme south of the African continent.” Furthermore, they avoided the doldrums close to the gulf of Guinea, as well as the winds of the right flank of the subtropical anticyclone that oppose sailing in a southerly direction.

The route designed by Vasco da Gama used the Large Loop for the first time in the history of sail navigation in the South Atlantic. On sailing to the south west, the ships made use of the Brazilian current and of the winds of the left flank of the subtropical anticyclone of the Atlantic, “avoiding numerous difficulties that they would have come up against on the route along the African coast.” There only remained one large obstacle confirmed by the team, “the greatest barrier to the expeditions was the Cape of Good Hope, where tropical cyclones are highly intense and generate extensive regions with strong winds and gigantic waves on the open sea.” The work relates a recent case with waves taller than 5 meters generated by a cyclone in the South Atlantic that made its way towards the cape of Good Hope.

“The expedition of Vasco da Gama was caught by surprise at the Cape of good Hope in November 1497 by an enormous storm on the outward voyage to India and almost all of the fleet sank in this region on the return trip in March of 1499, probably due to the intense cyclones migrating from the west.” Actually, the navigators had already known about the dangers and planned to enter into the region after October so as to avoid the worst weather. The researchers of Inpe felt the difficulties of the Portuguese navigators when analyzing what happens routinely at the Cape of Good Hope and when studying a specific event between the 11th and the 14th of June 1999, when two cyclones spawned winds and waves in the region. One of them was accompanied with surface winds with speed that went beyond 20 meters per second (72 km/h), enough to bring about waves five-meter high in an extensive region.

Not only did the experience and the bravery of the navigators play a major part in helping the adventurers cross the sea, it was the trysail canvases idealized by the savants of the “School of Sagres ” – Scholl of Navigators says Dr. Innocentini. “The trysail canvases were triangular sheets, capable of pushing the ships in a direction perpendicular to the wind. In this manner the navigators were able to beat the trade winds from the northeast that would have thwarted their return to Portugal.” He also points out that the astronomers and mathematicians of the “School of Sagres ” had developed tables for the declination of the stars as well as efficient navigational tools such as the astrolabe and the sextant, used to measure the position of the stars and to determine the position of the vessel. He concludes, “All of this development went on because of the necessity of new techniques, since that the knowledge that had been developed for sailing in the Mediterranean was inadequate for the Atlantic, the Tenebrous Sea as it was called at the time.”

The project
The Dynamics of Cyclic Genesis Concerning the South Atlantic (95/04573-5); Modality: Thematic project; Coordinator: Dr. Valdir Innocentini – The National Institute of Space Research (Inpe); Investment: R$ 39,230.05 and a further US$ 265,933.34

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