Professor Toshio Yamagata is one of the worlds leading climate scientists, his research findings include the discovery of the Indian Ocean Dipole. We had the pleasure of talking to Toshio last week. Here is his fascinating story.
Toshio, how did you end up becoming interested in climate science?
My hometown is about 100 kilometers north of Tokyo, and in the winter strong monsoon blows down from the mountainous areas. When I was a child, the dust from the fields was amazing. Thunderclouds come down with lightning from the mountainous areas every summer in the afternoons every day. In the spring, flowers bloomed in the gardens of each family, and in autumn, the foliage of deciduous trees was beautiful. My parents liked gardening, and I naturally became interested in the changing seasons.
At the University of Tokyo, I majored geophysics as a field where research can be done while enjoying nature. My supervisor was Professor Kozo Yoshida, who is famous for his research on coastal upwelling in the field of physical oceanography. I was interested in mathematical physics, so I chose the field of geophysical fluid dynamics (GFD), which treats fluid phenomena that occur on a rotating, stratified planet.
My younger work at that time includes the weak non-linear theory that explains why anticyclonic vortices keep longevity in the ocean and Jupiter, and the mechanism by which planetary waves become unstable to form vortices. In 1976, the GFD program of the Woods Hole Oceanographic Institution approved me to stay there for three months as a GFD fellow. This was an amazing opportunity to meet many giants in the field, such as Drs. Joe Pedlosky, Peter Rhines, Melvin Stern, Jack Whitehead, Geroge Veronis, Andrew Ingersoll, Willem Malkus, Louis Howard etc. They opened my young eyes to the world. In particular, main lecturer was Dr. Dick Lindzen; I was impressed by his simple Albedo-feedback model for climate. I didn't understand it well at the time, but I think it may have shaped the deep psychology of becoming a climate researcher.
After turning the age 30, I gradually wanted to deal with real phenomena that occur in the atmosphere and the ocean to understand the meaning of seasons, I daringly sent a letter with my articles to Dr. Kirk Bryan of GFDL at Princeton University in the United States, asking possibility of staying a couple of years as a visiting researcher. He immediately accepted me. There I met Dr. George Philander, and decided to go deeper into the study of tropical climate. This set the course of my life in science; it was in my early 30s. I moved to the US with my wife and my three-year-old son. At that time, I thought that the United States might become a place for my research. In retrospect, I think there are decisive moments in life that determine what follows.
When did you become suspicious that the Indian Ocean had a see-saw condition similar to the El Niño - La Niña phases in the Pacific Oceans?
The summer of 1994 was extremely hot in Japan, and a research team investigating the cause was formed by meteorologists. I had been studying El Niño model since I was in Princeton, so I joined the group. A little later, the AGU Western Pacific Geophysics Meeting was held in Brisbane, and I had the opportunity to exchange ideas with Dr. Gary Meyers of CSIRO. He informed me that there were abnormally dry conditions in Australia, and, according to his XBT section data, the eastern Indian Ocean was also colder than normal. We checked the oceanic semiannual Yoshida-Wyrtki Jet (which is trapped along the equator and flows eastward only during the monsoon break season: spring and fall) using the satellite data (SST and altimetry data) and found there was almost no eastward Yoshida-Wyrtki Jet in fall of 1994. It was amazing! This is the beginning of the story. It turned out that the unusual westward winds along the equator from early summer to late fall hindered the evolution of the fall Yoshida-Wyrtki Jet. By the way, the Yoshida-Wyrtki Jet (equatorial long Kelvin wave) was predicted theoretically by my supervisor Prof. Kozo Yoshida in the late 1950s and reported by Prof. Klaus Wyrtki in 1973 using the ship drift data. I was excited at finding this unusual event similar to El Nino in the Pacific and started checking all available atmospheric and oceanic data with my young postdocs from India. Those are Saji, Vinay and Behera. I named this Indian Ocean Dipole Mode and introduced the IOD index. There is another interesting story behind the scene just prior to publishing our paper in NATURE, but this will enter the realm of science historians.
