{"id":146732,"date":"2014-04-16T15:32:59","date_gmt":"2014-04-16T18:32:59","guid":{"rendered":"http:\/\/revistapesquisa.fapesp.br\/?p=146732"},"modified":"2015-12-21T16:49:31","modified_gmt":"2015-12-21T18:49:31","slug":"ocean-skies","status":"publish","type":"post","link":"https:\/\/revistapesquisa.fapesp.br\/en\/ocean-skies\/","title":{"rendered":"An ocean in the skies"},"content":{"rendered":"
\"A

Eduardo Cesar<\/span>A world of water: dark clouds over the Negro River and Manaus on February 18, 2014, harbingers of another Amazon rainfallEduardo Cesar<\/span><\/p><\/div>\n

From Manaus, Brazil<\/em><\/p>\n

Here in the city of Manaus and throughout this vast region of the North it rains a great deal throughout the year, but the rains are not all alike. Early in the year\u2014February and March\u2014it rains nearly every day, bathing the forest and the cities in showers that last for hours at a time but feature few instances of lightning. Late in the year\u2014September to November\u2014the storms are more intense and accompanied by enough electrical activity to awaken childhood fears, but the rainfall is localized and shorter in duration. In an effort to confirm and analyze the mechanisms of rain formation\u2014which differs in each region of Brazil, and even within regions\u2014and the effect of pollution in Manaus on climate in the Amazon, a group of 100 researchers from Brazil, the United States and Germany has begun to examine the sky around Manaus using radar and aircraft, under the auspices of the Green Ocean Amazon (GOAmazon) program. GOAmazon was officially launched on February 18, 2014 in Manaus, with a budget of R$24 million funded by FAPESP, the Amazonas Research Foundation (FAPEAM), the US Department of Energy and the National Science Foundation (NSF).<\/p>\n

The term \u201cgreen ocean\u201d was coined in 1999, during the first major campaign of the Large-Scale Biosphere-Atmosphere Experiment (LBA). While flying over the Ji-Paran\u00e1 Forest in the state of Rond\u00f4nia, researchers\u2014many of them now working under this new program\u2014noticed that the clouds were not behaving as expected. The clouds in this area of Amazonia near Bolivia were thought to be as high as 20 kilometers (km) and to contain a high concentration of particulates and droplets of rain\u2014characteristic of what are known as continental clouds. Instead, they had features of ocean clouds, with few particulates, more rapid formation and relatively low tops, as is typical in ocean areas. It was an ocean, but green rather than blue due to its position over the forest. Antonio Manzi, a researcher at the National Institute for Research in the Amazon (Inpa), who took part in that expedition and others for the LBA and is now a member of the GOAmazon team, remembers that 1999 was also the year in which they ascertained that so-called warm clouds, which do not form ice crystals, were prevalent in the region\u2014a surprising occurrence in continental areas.<\/p>\n

\"\"INFOGRAPHIC ANA PAULA CAMPOS ILLUSTRATION FABIO OTUBO <\/span><\/a>The volume of rain that falls over the Amazon Basin is equivalent to an ocean\u201427 trillion metric tons of rain each year on average, according to Manzi. Viewed in more concrete terms, were the rain to accumulate instead of filtering into the soil, it would form a sheet of water 2.3 meters deep along the 6.1 million square kilometers of the Amazon Basin, which extends through Brazil and several neighboring countries. Luiz Augusto Machado, a researcher at the National Institute for Space Research (INPE), calculated the average volume of rainfall throughout Brazil at 14 trillion metric tons per year. If the rain accumulated, it would submerge the entire country under a layer of water 1.7 meters deep. Machado also coordinates Projeto Chuva (the Rain Project), a component of GOAmazon, and now, in Manaus, he will conduct the final phase of a survey of the types and distribution of rain clouds in Brazil.<\/p>\n

It is not yet clear how this aerial ocean forms. \u201cClouds may or may not produce rain,\u201d says Gilberto Fisch of the Aeronautics and Space Institute (IAE) in S\u00e3o Jos\u00e9 dos Campos, a researcher with Projeto Chuva. \u201cWe often say that when there is water vapor, rain forms and then falls, but that is not always the case.\u201d Most cloud-forming droplets, which are tens of micrometers in diameter, disperse in the form of vapor. Only a small number grow in volume and become drops of one to five millimeters that fall because of gravity. Understanding how clouds form and grow, and in which ones rain actually forms, is one of the goals of the GOAmazon team.<\/p>\n

At one of the data collection points in the municipality of Manacapuru, 80 km west of Manaus, 120 instruments are operating day and night\u2014some of them exposed, others housed inside 15 containers\u2014collecting regional climate data. These are augmented by weather balloons released every six hours. Atop one of the containers is a radar instrument with a 100-km range that studies the shape and composition of rain-forming clouds. This type of instrument has performed the same service in other Brazilian cities since 2010. The cloud data will be collated with the data from the GPM (Global Precipitation Measurement) satellite, which is expected to be launched on February 27, 2014 from Japan and remain in orbit at an altitude of 400 km, sending data on rain clouds over nearly the entire planet. \u201cThe GPM will pass over Manaus twice a day, supplementing our data,\u201d Machado says.<\/p>\n

A research aircraft from the United States arrived in Manaus on February 16 and was expected to begin flying in the next few days to directly examine the types of ice crystals inside the clouds and measure levels of carbon dioxide (CO2<\/sub>) and particulates. Plans are for the US plane and another aircraft from Germany to fly over the city and the forest in September to measure any climate changes in the dry season.<\/span><\/p>\n

The experiments, to be completed in December 2015, are expected to generate short-term (two-hour) weather forecasts and more accurate computer models of atmospheric circulation. In some areas of Brazil, rainfall monitoring, which relies on weather satellites, is still very inaccurate, causing delays in alerts that could save lives before heavy rains arrive.<\/p>\n

\"Sweeping

Eduardo Cesar<\/span>Sweeping the sky: cloud radar (left) and rain radar instruments in Manacapuru, 80 km from ManausEduardo Cesar<\/span><\/p><\/div>\n

A metropolis in the forest
\n<\/b>With a strong industrial base, 700,000 vehicles and nearly two million residents, Manaus, capital of the state of Amazonas, is the world\u2019s largest tropical metropolis and is surrounded by hundreds of kilometers of forest. How does the pollution plume produced by this megacity in the middle of Amazonia alter the life cycle of the aerosols and clouds in forest preserve areas, and how do these elements interact in the atmosphere and cause more or less rain in the region?<\/p>\n

These are the key questions that the international GOAmazon experiment will attempt to answer in the years to come. A detailed set of measurements of aerosols, trace gases (carbon dioxide, methane and other gases) and clouds will be taken at six different sites. Three are located to the east, ahead of the prevailing winds over Manaus, so the atmosphere over these sites is not yet contaminated by the city\u2019s pollution plume. A fourth measurement station will be located in the city itself, and the remaining two are to the west in Iranduba and Manacapuru, where the atmosphere is already laden with the effect of the pollutants emitted in Manaus.<\/p>\n

\u201cNo other city has a scenario like that of the capital of Amazonas,\u201d notes Paulo Artaxo, coordinator of the thematic project linked to GOAmazon. \u201cWe know that pollution alters precipitation, but in what type of cloud and under what circumstances?\u201d Studies conducted by Scott Martin, a researcher at Harvard University and member of the GOAmazon team, have indicated that the effect of aerosols on climate in the Amazon varies depending on the time of year. It has also been observed that clouds passing over the city take on pollution and have higher reflectivity than those without pollution. The clouds over the forest have a particulate load equivalent to that of pre-industrial times.<\/p>\n