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Noboru Nakamura by Edward Olsen

How many members of the Geophysical Sciences faculty have had a special showing of their art work? As far as we know, only Noboru Nakamura. He paints, he sculpts, and he makes ceramic pieces. These are a far departure from atmospheric physics and those frighteningly complex differential equations that describe fluid flow. How did a young man in Japan, with strong artistic leanings, end up as a professor of atmospheric dynamics at the University of Chicago?

When he was young he was involved in mountaineering. For years he belonged to a mountaineering club that made careful preparations before doing climbs. One of the preparation jobs was to collect current weather data and draw maps so there would be no surprises on the slopes. Noboru was picked to be the weather man for the club. Up to that time his interest in the sky and atmosphere was solely to gaze at the interesting shapes in clouds and delight in spectacular sunrises and sunsets. Preparing weather information for a mountain climb was more serious stuff. As time went on he became more and more intrigued with the motions of weather systems and curious about what drives and controls weather. Suddenly meteorology was appealing as a career option.

While Noboru had to make a tough choice between art and science, all of this was a little disturbing to his parents. He is an only child and they were concerned that he go into some profession that would give him financial security - something like economics or business administration. Nevertheless they thought science was better than art. Noboru went to the University of Tokyo, where he majored in geophysics but also participated in a wide-ranging extracurricular activities including Sumo wrestling.

After completing his undergraduate degree at Tokyo, he applied for graduate school at Princeton. Because his undergraduate record was somewhat "less-than-optimal" for science, his application for graduate work in atmospheric physics was not a simple decision. At the time, Professor Suki Manabe, one of the world's great climatologists, was on the faculty at Princeton. He looked at the transcript and intervened on Noboru's behalf. Noboru was accepted and Manabe is his hero to this day.

At Princeton Noboru took courses in fluid dynamics during the day and learned the concepts necessary for understanding atmospheric circulation and storms, while at night he spent hours in the art studio to work on various media. He received his Ph.D. in 1989 in Atmospheric Science, immediately followed by a showing of his art work in the Visual Art Department, which was well received.

He first entered a postdoctoral position at the University of Washington in Seattle. He worked there under Mike Wallace. Then, in 1990, he returned to Princeton for a second postdoc. In the autumn of 1992 he was hired by Chicago.

Noboru is a great admirer of Dave Fultz. Early in his undergraduate school work he read about Dave's experiments at Chicago and how they elucidated the dynamics of jet streams. He never thought he would be teaching at Dave Fultz's university. During his first years at Chicago Dave would occasionally pop into Noboru's classes to listen. Noboru was delighted by that. As he has developed his course work he has incorporated small, portable, reproductions of Dave Fultz's experiments. He finds them to be great teaching tools and the students react very positively to these physical models.

Lately Noboru has focused his research on the fluid dynamical problem of the transport of trace gases and aerosols through the upper atmosphere and around the earth. Transport across latitudes is especially important to understand. Pollutants from the northern hemisphere ultimately penetrate through into the southern hemisphere. The most famous case is that of the (much publicized) production and release of chlorinated hydrocarbon compounds (CFCs) in the industrial countries of the northern hemisphere. These compounds move across latitudes, eventually into the Antarctica where they are chemically very efficient (due to low temperatures) in the process of destroying the ozone layer of the stratosphere. This results in the annual "ozone hole" that has been so much in the news in recent years.

CFC transport is only one case. When large volcanoes erupt they propel huge amounts of fine volcanic ash into the upper atmosphere. This can temporarily affect the climate over large continental regions by reducing the amount of solar radiation reaching down, but the regional effects are modulated by the transport process. Exhausts from supersonic transports (SSTs) that fly in the tropics can also alter atmospheric chemistry of the polar region if there is fast cross-latitude transport.

What drives cross-latitude transport? In the stratosphere, it is the large-scale waves and eddies created by surface topography and land-sea contrasts. From our experience with a smooth jet ride we tend to think that the stratosphere is a serene place, but on a large horizontal scale it is quite violent particularly in winter. Understanding and successfully quantifying cross-latitude transport is tricky. Jet streams steer air masses across the continents. A pollutant, released from a particular region, has to punch through a jet stream or two in order to spread to the other hemisphere. This isn't always easy.

In the case of ozone destruction, for example, it is interesting that in the Arctic there is no large ozone hole development, even though CFCs are initially released primarily from the northern hemisphere. The Arctic, however, has a very different regime from the Antarctic. There is much more land mass in the north, hence much more topography that can create eddies. The eddies can move CFCs, however, they also promote the movement of heat from lower latitudes into the Arctic regions. The warmer spring air in the Arctic is not conducive to the formation of stratospheric ice crystals, which are the surfaces on which the chemical reactions that destroy ozone take place.

In the south there is only the Antarctic continent surrounded entirely by large uninterrupted of ocean, with no topography, and a weaker eddy formation regime. Antarctica is thus much colder than the Arctic polar regions, and an ideal place for high level ice crystal formation and ozone destruction.

Noboru has constructed novel methods to quantify diffusive transport. His methods are built around fine scale geometry of constituents. The finer the structure, the more efficient they are at being diffused. He uses fluid dynamical equations to extract geometrical information on diffusivity. He follows the courses of two gases from satellite measurements, nitrous oxide and methane, to infer transport across latitudes. Unfortunately, current satellite systems are only capable of rather coarse scale horizontal resolution - hundred kilometers or so at best. But even from these data he discovered that diffusivities are indeed minimal at the jet streams--a result everybody suspected but nobody was able to quantify. He hopes, that in the near future NASA will be able to provide instrumentation for higher resolution horizontal measurements in the stratosphere. Until that time, his methods will be used by atmospheric scientists to follow the diffusion of pollutants around the planet.