Everyone who flies has experienced turbulence – that uncomfortable sensation of dropping and shaking that happens as an airplane flies through a mass of unstable air. It’s always unpleasant, and can even be dangerous in some cases. Scientists have struggled for a long time to understand and predict turbulence and its effect on aircraft, automobiles, buildings and other common objects, but its causes have largely remained a mystery. Now St. John’s-based scientist Jahrul Alam is making inroads in the study of turbulence and he’s using a lot of computational muscle to conduct his research. Alam is an associate professor of mathematics at Memorial University of Newfoundland and an expert in the field of atmospheric turbulence. “I try to characterize atmospheric turbulence mathematically,” he says. To do that he’s harnessing the computing power of ACENET, using a mathematical simulation model called adaptive wavelet large eddy simulation. Turbulence is a complex process involving millions of tiny variables. To try and understand how it works Alam cuts his data down into atmospheric samples that measure 500 cubic meters in volume. “The smaller the sample the more accurately we can study the process, but turbulence has such huge degrees of freedom that we have to filter the data into manageable portions,” he says. “We could never measure it if we broke it down into something like cubic centimetres, for example. The calculations would be too large.” One of the great enigmas about turbulence is the fact that there is so much of it in places like Atlantic Canada where the ground is often cold. It’s one of the questions that Alam seeks to answer with his calculations. “We know that turbulence is created by heat rising from warm ground, but we don’t really understand why it would be so intense in places where the ground is cold,” he says. “Or at night.” In regions with a cool ground, episodes of wind gusting often manifest as short turbulence bursts, making it even more complicated to measure and predict. Varying ground conditions also add complexity to the study, says Alam. “When wind hits mountains, trees or buildings, turbulence is sometimes enhanced by the interaction.” Alam’s research will ultimately have huge practical applications in fields such as airline safety, structural design and environmental science. With climate change, incidences of serious turbulence will increase, he says – particularly the headline-grabbing incidents that involve injured passengers, aircraft damage and emergency landings. “If we can understand turbulence, maybe we can learn to predict it more accurately so that aircraft can avoid it,” says Alam. Alam says his study using wavelets and the ACENET computer network is unique and is producing some significant results. “These are techniques that very few people in the world are using,” he says. Climate change is also making Alam’s work more pressing. “If we continue global warming, the incidences of atmospheric turbulence will increase,” he says. At the same time, humans are constantly changing the surface of the planet by cutting down forests, building tall buildings and reengineering the ground. All of it has an impact on turbulence. “We need to understand it so that we can predict it and design better structures, and better aircraft and automobiles to deal with it.”
Showcase Tag: Atmospheric Science
Taking the Earth’s Temperature
The greenhouse effect is nothing new. In fact the phenomenon has been influencing the temperature of the Earth for billions of years. The existence of carbon dioxide molecules in the atmosphere acts as a blanket, trapping heat and allowing the Earth’s temperature to remain warmer than it would be otherwise. But in the last 200 years, human activity has been adding greenhouse gases into the atmosphere at rates exceeding any natural process, making the carbon dioxide blanket thicker and warming the Earth even more. As the planet warms up, most of the additional energy from the enhanced greenhouse effect is stored in the ocean – about 93% in total. The rest is distributed among the continents, in the frozen ices known as the cryosphere, and in the atmosphere. Dr. Hugo Beltrami is a professor at the Climate & Atmospheric Sciences Institute, the Environmental Sciences Program at St. Francis Xavier University and a new Canada Research Chair in Climate Dynamics. He and his graduate students conduct research in the area of global-scale climate change. They are using geothermal data obtained from mining exploration boreholes, reaching deep into the ground to study the changes of the temperature at the continental surface during the last millennium. It’s a complicated process. “We have to go down about 500 metres just to measure the remnants of past ground surface temperature changes that occurred in the last millennium,” he says. “If we want to estimate changes further in the past, we have to go much deeper.” Beltrami’s research is attempting to measure how much energy is stored in the ground and also how energy is distributed between the ground and the atmosphere. It’s critical information for environmentalists, policy makers, planners and scientists. As the ground becomes warmer, more carbon dioxide is released from soils, increasing the atmospheric concentration of greenhouse gases. Another aspect of Beltrami’s work relates to regional climate modelling. For example, he and his graduate students have conducted extensive research to project the potential effects of climate change on the propagation of the tick that carries Lyme disease in Nova Scotia and Ontario. He is also developing a climate services centre that will translate global climate model predictions into information that is useful at a local level. The information would allow individual municipalities to access local climate projections, increasing awareness of the potential consequences of climate change on things like infrastructure and public health. The service may also help to support the development of policies to build resilience and mitigate the societal impacts of a changing regional climate. Every part of Beltrami’s research requires his team to use intensive numerical modelling. The numbers are huge and the calculations would be impossible to run on a regular computer. He’s been a user of ACENET since the program started. “ACENET is an essential resource for us,” he says.
Advanced Computing Helps Scientists Track Air Pollution
The health hazards and environmental impacts of emissions from industry, vehicles and other sources are well established: cardiovascular disease, asthma and premature deaths, as well as crop damage and disease outbreaks in certain tree species. Yet little is known about how particulate matter – tiny invisible specks of mineral dust, carbon and other chemicals – moves through the atmosphere and its effects on the health of local populations around the world. That’s changing thanks to the work of Dr. Randall Martin, an atmospheric scientist who uses remote sensing satellites, computer modeling and advanced research computing to identify the trends and magnitude of human exposure to these pollutants. Martin was among six Canadian researchers who met with MPs and Senators on Parliament Hill December 2nd to showcase how government investments in advanced research computing are having an impact internationally, nationally and locally. Organized by Compute Canada and co-hosted by the House of Commons speaker Andrew Scheer, the event attracted several Parliamentarians, including Senator Kelvin Ogilvie, and Minister of State (Science and Technology) Ed Holder who spoke about the importance of advanced computing to many of Canada’s biggest science projects. “Researchers in Canada generate data of unprecedented size and complexity, and our government is committed to ensuring that Canada stays at the cutting edge of this technology,” said Holder. For example, global modeling and the analysis of satellite data require intense calculations and vast data storage – expensive, state-of-the-art technologies that Martin and his team are able to access via ACENET and Compute Canada. “We wouldn’t be able to answer these scientific questions without this level of computational power,” said Martin. “These tools allow us to collaborate with Health Canada and Environment Canada to contribute to science-based decision making to protect the health and well-being of Canadians.” The Atmospheric Composition Analysis Group at Dalhousie is the only research group in the world that has applied satellite remote sensing to infer long-term concentrations of global, ground-level fine particulate matter. Traditional ground-based instruments for monitoring air pollution are located primarily in urban areas, leaving rural and remote communities with no data on the quality of the air they breathe. Martin’s group is able to paint a more comprehensive and accurate picture of air pollution for geographic regions as small as 10 kilometres, using publicly available satellite data generated over the past decade from space agencies around the world, including NASA. “NASA has invested billions of dollars in the preparation and launch of these satellites and in the data collection, and for relatively modest investments here in terms of computing and people, we can leverage that substantial investment,” he said. The biggest surprises from the research have been in areas of south and east Asia, north Africa and the Middle East where coal-fired generating plants and wind-blown mineral dust have contributed to significant air pollution. Other pollution “hot spots” were identified over eastern North America and northern Europe. This research is helping scientists and policymakers understand how chemicals in the atmosphere affect climate change and air quality. The Canadian government used Martin’s data to develop more stringent and comprehensive air quality standards for fine particulate matter, a major component of smog. His team’s work has also contributed to several high-profile global assessments conducted by the Organisation for Economic Co-operation and Development (OECD), the World Health Organization (WHO) and other international agencies. Martin’s group has also had a leading role in the development of an open-source, global, three-dimensional model of atmospheric composition called GEOS–Chem, which is used by more than 70 institutions worldwide. It allows assessment of sources and processes that affect air quality. “One possible benefit from our research is increased life expectancy for people around the world due to improved policies that clean the air that we breathe,” said Martin. “It could also contribute to a better understanding of the effects of human activities on climate change and lead to more informed decisions about how we might best deal with this complex issue.”
Understanding Greenhouse Gases
Karine Le Bris is an associate professor of physics at St. Francis Xavier University. Her research centres around the development of new optical detection techniques and characterization of greenhouse gases in the atmosphere. Part of her research involves the identification of the spectral signatures of greenhouse gases and the calculation of their global warming potential, a measure of the amount of heat a particular greenhouse gas traps in the atmosphere. The knowledge of the spectral signatures allows the detection of atmospheric gases using optical ground-based techniques or Earth-orbiting satellites, while the global warming potentials identify which gases should be mitigated in priority. The spectral signatures of most greenhouse gases are usually found experimentally using a device called a Fourier transform spectrometer, says Dr. Le Bris. However, the instrument does not always allow scientists access to the full spectral range of the gas. Sometimes, the isomeric composition of the gas is also not known. “Using a method called density functional theory, the spectral signature of a molecule – how much light a gas absorbs at a particular wavelength – can be estimated,” she says. “By comparing the theoretical data to the experimental ones, we can simulate the spectrum outside of the experimental range and sometimes have access to the isomeric distribution.” Dr. Le Bris enjoys spending time in the lab and conducts much of her research there, but she also relies on ACENET. “I’m mostly an experimentalist,” she says. “But I can’t do everything experimentally.” She uses the ACENET advanced computer systems to optimize the geometry of each isomer and find their vibrational frequencies – complex calculations that often take hours to run. “They are not the types of calculations I could do in a timely manner with a regular computer,” she says. While she admits to being motivated by a love of pure scientific research, Dr. Le Bris says that her work offers other researchers and scientists valuable data that they can use to understand and predict changes in the atmosphere – information that can help scientists, environmentalists and civic planners respond to the effects of climate change. “If we understand climate change in advance it helps us be prepared to deal with it.”