What are you researching?

Fig. 1 The cover of Nature, featuring an article by us (March 2008). The blue and white in the diagram represents the ocean surface flow rate, with the white indicating the Gulf Stream. The yellow and orange above it is the tropospheric rising wind speed, showing a strong rising wind directly above the Gulf Stream

The reason why Earth is “the planet of life” is the fact that it has the “sky” and the “sea,” in other words, an atmosphere and an ocean. I am engaged in research looking into how these two major fluids on the earth interact and impact one another, known as atmosphere/ocean interaction. The resultant climate variability and change are also our research targets. We know quite a lot about how the atmosphere affects the oceans. However, we know much less about how the ocean influences the atmosphere, because we have very little meteorological observational data over the oceans. Recently, however, new satellite measurements and higher resolution numerical modellings, which are significantly improved from conventional methods, have allowed us to see interactions that we could never imagined before. 

What sort of research are you engaged in?

We are engaged in the analysis of a range of measurement data, with the aim of making new discoveries. For example, Fig. 1 shows an average updraft penetrating across the troposphere directly above the Gulf Stream in the North Atlantic. This was the first time this type of phenomenon had been observed. With this research, we further discovered that precipitation is concentrated in a narrow area above the Gulf Stream, indicating that a band of precipitation has been anchored by the strong current (Fig. 2a).

Fig. 2 Annual average precipitation values (color). The precipitation values are respectively obtained by (a) satellite precipitation measurement, (b) atmospheric circulation simulation with measured surface water temperature supplied, and (c) atmospheric circulation simulation with smoothed surface water temperature supplied. The green arrow in panel (a) represents the Gulf Stream. The contours represent ocean surface water temperatures

On the other hand, we are also engaged in numerical experiments in order to clarify mechanisms of various phenomena. In the example above, if the precipitation band is actually anchored by the Gulf Stream, then this band of precipitation ought to disappear if the Gulf Stream were stopped. Since we cannot stop the real Gulf Stream, in order to confirm this hypothesis we conduct experiments using a numerical model, which represents the atmosphere and ocean as numerical values on a computer. In one experiment, we used observed values for surface water temperature, which transfer ocean’s information to the atmosphere, and obtained realistic band of precipitation over the Gulf Stream (Fig. 2b). This confirmed that our numerical model can simulate the traget feature. In the other experiment, we smoothed out the water temperature gradient, which is steep over the Gulf Stream, and saw that this narrow precipitation band no longer occurs (Fig. 2c). This clearly showed that the precipitation band was caused by the Gulf Stream .

Fig. 3 (A) Average annual values for ocean surface pressure during winter in the North Pacific. To the north, the average area of low pressure known as Aleutian low pressure is clearly seen. (B) The strength of Aleutian low pressure (black), the averaged ocean surface pressure within the red box in (A), and the averages for 1950-1976 and 1977-2010 (red). Aleutian low pressure became rapidly stronger in the 1970s (the atmospheric pressure of the low pressure area became lower), a phenomenon known as a climatic regime shift.

Furthermore, it has been established that the Kuroshio Current near Japan also has similar impacts on the atmosphere. These results stimulate a number of international researchers to investigate how interactions between atmosphere and ocean impact, for example, climate variability and change over the North Pacific (Fig. 3).

What would you like to achieve in the future?

Fig. 4 Students take meteorological measurements.

First, I would like to attempt a fusion of numerical calculation and data analysis. Our third-year students are experimenting with meteorological measurement (Fig. 4) and learning to read the data they obtain.

Additionally, I would like to further develop atmospheric and oceanic research. Hokkaido University has made a great contribution to researching atmosphere/ocean interaction, and in a 2010-2014 national-level research project, four of the nine representative researchers either studied at or belonged to Hokkaido University. I hope we can continue to produce such world-leading research results.

I do hope that any students who are interested in research or becoming researchers will come along and develop their ability and skill with us. It is great pleasure to see students grow.

Discovering new phenomena within nature and explaining their mechanisms are very exciting experiences. When you find something completely unexpected, you will stand up and shout about it. I hope that I can let you know the joy of research.

Earth and planetary sciences involves various research areas: not only the atmosphere and the ocean, but also solid earth and planetary research, and even those with chemical and biological standpoints. I am sure that you will find an aspect of earth and planetary sciences that you’ll enjoy in our university.

References

(1) Minobe S. (joint), Climate Change in Japan and Changes to the Atmosphere and Ocean at Middle and High Latitudes, in “Oceans and Environment – Change the Ocean and Change the Earth,” Oceanographic Society of Japan (ed.) pp. 88-98, Kodansha (2001).

 

[1]A more detailed explanation can be found at　http://www.sci.hokudai.ac.jp/~minobe/kaisetsu