Dr. Knut Stamnes' Seminal Paper Informs Research in Climate Change, "Greenhouse" Effect

Stevens Professor's is the most cited in the 50-year history of the influential journal Applied Optics


Professor Knut Stamnes of the Stevens Department of Physics and Engineering Physics is renowned for simplifying the process now used to remotely sense the particles in the atmosphere, the microbiological constituents of the ocean, and the composition of sheets of ice and snow. His incisive 1989 article introduced a new mathematical algorithm for the calculation of radiative transfer through layered material, and it continues to be a vital contribution to researchers around the world.

It is particularly valuable to atmospheric research because radiative transfer and energy balance essentially comprise the Earth’s climate. If, for example, incoming radiation increases without a subsequent increase in outgoing radiation, the energy balance of our atmosphere is reestablished by an increase in temperature. This is often described as the “greenhouse” effect. By enabling researchers to calculate radiative transfer in the atmosphere, Dr. Stamnes’ article helps to study and model the climate.

Applied Optics declares it the most cited article of the journal’s 50-year history in its recently released anniversary list.

“Dr. Stamnes’ research has proven indispensable for his peers and for researchers across multiple disciplines,” says Dr. Michael Bruno, Dean of the Charles V. Schaefer, Jr. School of Engineering and Science. ”The Applied Optics anniversary ranking makes the scope of its impact clear.”

The pivotal article, titled “Numerically stable algorithm for discrete-ordinate-method radiative transfer in multiple scattering and emitting layered media”, has become a benchmark for further innovation in the field of radiative transfer, and Dr. Stamnes uses the algorithm and the principles that underpin it to this day.

Dr. Stamnes and his collaborators Si-Chee Tsay and Warren Wiscombe of NASA, and Kolf Jayaweera of CSU Fullerton made it simple for researchers to determine the composition of a material by measuring how radiation—light, for instance— moves through it. They outlined a mathematical procedure and developed a computer program which allows researchers to calculate the transfer of radiation through a plane-parallel material based on the known optical properties of a system. They can thus measure the distribution of light transmitted through or reflected from a substance and compare observations with their calculations to determine its composition.

The approach has been exceedingly useful, with diverse applications in fields such as the study of aerosols, clouds, the atmosphere, and the climate; astronomy; and the propagation of light in organic tissue.

Because satellites pick up radiation from the earth in a process called passive remote sensing, Dr. Stamnes’ algorithm can be applied to study distant and inaccessible areas of the planet. This enables the detection of algal blooms, particles, and dissolved organic matter in the ocean, as well as the examination of radiative properties of snow and ice. Scientists use remote sensing to study the health of the ocean, vegetation rates, erosion, pollution, forestry, weather, and land use.

Dr. Stamnes currently uses the algorithm and its related principles to study the propagation of light in tissue. Light travels through tumors differently than it does through healthy tissue, and a device based on Dr. Stamnes’ algorithm would help distinguish the two in a simple and non-invasive manner. This makes for easier and more accurate skin cancer screenings, allowing doctors to detect tumors earlier and thus give treatment the greatest opportunity for success.

“The breadth of applications of Dr. Stamnes’ work is remarkable,” notes Dr. Rainer Martini, Director of the Department of Physics and Engineering Physics. “It is exhilarating to see the progression from theory and mathematical equations to the climate models cited in news and government policy, or a new screening method at a doctor’s office.”

Dr. Stamnes feels there is still much work to be done on remote sensing.

“New discoveries and applications have illuminated whole new areas of study within applied optics, and the research is extremely vibrant,” he says. “Remote sensing is a particularly competitive field, but with our capabilities Stevens can play a big role in its future.”

His research has been funded by the National Science Foundation, the U.S. Department of Energy, National Aeronautics and Space Agency, National Oceanic and Atmospheric Administration, and the Japanese Aerospace Exploration Agency.